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L-Carnitine: what the studies show, status and safety

Status at a glance

MarketStatusDate
United StatesApproved, prescription only1985-12-27
European UnionApproved, prescription only—
GermanyScheduled substance—
United KingdomApproved, prescription only2025-06-16
AustraliaNot established—
CanadaApproved, prescription only1995-12-31
SwitzerlandApproved, prescription only—
Development stage
Approved
Strongest evidence
Meta-analysis
WADA status
Not listed
Last verified
2026-09-10
Version
1.0

Sold as a supplement. No injectable form is approved in any market.

L-Carnitine: what the studies show, status and safety

Summary

L-Carnitine is not a peptide. It is a small molecule the body builds for itself and also gets from food, above all red meat. Its job is to ferry long-chain fats into the part of the cell that burns them. Four countries license it as a prescription medicine for rare metabolic disorders and for dialysis patients. The same substance is sold freely as a supplement to swallow. The weight trials find about one kilogram, and the effect fades the longer people take it. Europe's food safety authority has turned down every health claim put to it.

Key findings at a glance

  • A prescription medicine in four countries since 27 December 1985. The United States approved it first, the injection followed on 16 December 1992. The United Kingdom, Canada and Switzerland classify it as prescription-only. Germany makes only the injected form prescription-only, so capsules stay on the shelf [1], [2], [3], [4], [5].
  • Europe has rejected every health claim. The food safety authority ruled against claims on cholesterol, sperm, energy metabolism and pregnancy in 2011. A fat metabolism claim was turned down in 2018 [6], [7].
  • About one kilogram, and it shrinks over time. Nine trials in 911 adults found 1.33 kg less weight than in the control groups. Thirty-seven trials in 2,292 adults found 1.21 kg. The effect fell significantly the longer people took it, p = 0.002 [8], [9].
  • Swallowing it does not fill the muscle. Muscle carnitine rose by 21 per cent only when high insulin levels were forced at the same time. That took 24 weeks [10].
  • The gut turns it into a metabolite tied to heart risk. People who eat meat made more than twenty times as much labelled TMAO as vegans and vegetarians, p = 0.001. High TMAO carried a relative risk of 1.62 for major cardiac events across 19 studies in 19,256 people [11], [12].
  • The hard outcome trials failed. A heart attack trial in 2,330 patients missed its main target, 9.2 against 10.5 per cent, p = 0.27. A sepsis trial in 250 patients missed its target. A cancer trial of the acetyl form made nerve damage worse, p = 0.01 [13], [14], [15].
  • Not on the doping list, but the drip can still be. The 2026 list does not name it. It does prohibit infusions above 100 millilitres per 12 hours, whatever they contain. The banned drug meldonium works the opposite way and lowers muscle carnitine [16].

What it is

L-Carnitine is a small molecule with seven carbon atoms, and it carries a permanent positive and negative charge at the same time. Chemists call that a betaine. It contains no amino acids joined end to end, so it has no peptide bond and no sequence [17].

The body makes it from the amino acids lysine and methionine in five steps, and the last step happens mostly in the liver. An adult carries about 20 grams of it, nearly all of it in skeletal muscle. Beef is by far the richest food source; salmon holds roughly twelve times less [18], [19].

As a medicine it is called levocarnitine. Sigma-Tau, today Leadiant Biosciences, holds the original American approvals for the brand Carnitor. The Swiss market carries Carnitene, the British one a paediatric oral solution [1], [4], [2].

Quick facts

FieldValueRef
NameL-Carnitine; as a medicine, levocarnitine[17], [20]
ClassQuaternary ammonium betaine, a vitamin-like nutrient made by the body. Not a peptide[17]
StructureSingle small molecule, no amino acids joined together, no peptide bond[17]
Formula and massC7H15NO3, 161.20 g/mol[17]
StereochemistryOnly the L-form works; the D-form disturbs carnitine-dependent processes[17], [21]
Half-life17.4 hours after infusion, following a fast distribution phase of 0.585 hours[21]
Absorption14 to 18 per cent from supplement amounts, against 54 to 87 per cent from ordinary food[22]
StatusPrescription medicine in the United States, United Kingdom, Canada and Switzerland; free food ingredient by mouth in the European Union[1], [2], [3], [4], [23]
OriginatorSigma-Tau, today Leadiant Biosciences[1]
ATC codeA16AA01[20]
CAS registry number541-15-1[17]
UNII0G389FZZ9M[17]
PubChem CID10917[17]
InChIKeyPHIQHXFUZVPYII-ZCFIWIBFSA-N[17]
DrugBankDB00583[24]

L-Carnitine: what the studies show, status and safety

How it works

The biochemistry is settled textbook material. What it does not explain is why adding more should change anything in someone who already has enough [21].

  • It is the ferry for fat. Long-chain fatty acids cannot cross the inner membrane of the mitochondrion on their own. Attached to carnitine they can, which is how they reach the machinery that burns them [21].
  • It buffers a second chemical balance. Inside the mitochondrion it soaks up surplus acetyl groups, which keeps free coenzyme A available for other reactions [25].
  • It gets into tissue through one door. A sodium-dependent transporter called OCTN2 pulls it into cells. When that transporter is faulty, the inherited form of carnitine deficiency follows [21].
  • The muscle store is hard to move. In healthy people the content only rose when insulin was pushed high at the same time, which took either a five-hour infusion in the laboratory or months of carbohydrate loading in a trial. Carnitine alone left the store unchanged [25], [10].
  • The kidney defends the level it wants. Normally 90 to 99 per cent of the filtered amount is reabsorbed. Push the blood level up and that efficiency drops, so the level falls back quickly [22].

That last point matters for the whole page. The body treats carnitine as something to keep constant, not as something to be topped up.

What the trials found

L-Carnitine is one of the most heavily studied supplements in existence. The pattern that emerges is consistent: small effects on measurements, and failure on the outcomes that decide whether people live better or longer.

Weight and body composition

Meta-analysis of randomised trials Nine trials in 911 adults found a mean difference of 1.33 kg against control. The 95 per cent confidence interval ran from 2.09 to 0.57 kg, and BMI fell by 0.47 points. A meta-regression showed the effect shrinking significantly as trials ran longer, p = 0.002 [8].

Meta-analysis of randomised trials The largest analysis pooled 37 trials in 2,292 adults. Weight fell by 1.21 kg, p below 0.001, BMI by 0.24 points, fat mass by 2.08 kg. Waist circumference and body fat percentage did not change. Restricting the pool to high-quality trials left only the weight effect standing [9].

What the weight meta-analyses actually found
9 trials, 911 adults
−1.33kg less than control
37 trials, 2,292 adults
−1.21kg less than control
43 trials, overweight and obese
−1.13kg less than control
8 meta-analyses, 16,352 people
−1.11kg less than control

Four separate pooled analyses of randomised trials, not a head-to-head comparison. The intervals overlap and all four land close to one kilogram. Sources [8], [9], [26], [27].

Meta-analysis of randomised trials An updated pool of 43 trials found 1.129 kg, interval 1.590 to 0.669. Statistical scatter between trials was high, at 63.4 per cent.

Body fat percentage did not move, at 0.874 per cent with an interval from 1.890 below to 0.142 above zero. The effect appeared only alongside lifestyle change, and not at all in dialysis patients [26].

Umbrella review Eight meta-analyses covering 16,352 people confirmed the size rather than changing it. Weight fell 1.11 kg, p = 0.005, and BMI 0.33 points, p = 0.026. Scatter between analyses reached 90.6 per cent. Trials ran between 8 and 30 weeks [27].

Muscle carnitine and fuel use

Randomised controlled trial Fourteen healthy young men took part over 24 weeks with muscle biopsies. Muscle carnitine rose by 21 per cent, p below 0.05, and stayed flat in the control group.

At moderate effort the carnitine group used 55 per cent less muscle glycogen. At hard effort lactate was 44 per cent lower and work output 11 per cent above baseline. Muscle carnitine rose only in the group that also received a large carbohydrate load, which pushes insulin up. Carnitine on its own did not move the store [10].

Controlled trial In twelve healthy men over 12 weeks, the carbohydrate-only group gained 1.9 kg of weight and 1.8 kg of fat, p below 0.05. The carnitine group gained neither. Muscle carnitine rose 20 per cent and whole-body energy expenditure 6 per cent. Six men per group is a very small study [28].

Randomised controlled trial Fourteen healthy men averaging 69 years took it for 25 weeks. Muscle carnitine rose from 20.1 to 23.9 millimoles per kilogram of dry muscle, p below 0.01. Fat oxidation during exercise rose 20 per cent. Insulin sensitivity did not change at all [29].

Muscle soreness and exercise

Meta-analysis of randomised trials Seven trials found less soreness at all five measurement points, from immediately after exercise to 96 hours later. Creatine kinase, myoglobin and lactate dehydrogenase were lower only at 24 hours. The effect showed up in resistance-training groups and in untrained people [30].

Umbrella review Across 53 meta-analyses, L-carnitine lowered creatine kinase and soreness with moderate certainty under the GRADE system. It sits in the same band as HMB, branched-chain amino acids, curcumin and ginseng [31].

Systematic review Eleven performance studies were reviewed without pooling, five giving it for 4 to 24 weeks and six as a single dose. Reported findings included lower perceived effort and higher peak power. The authors declined to combine such different preparations into one number [32].

Blood sugar, blood fats and liver enzymes

Meta-analysis of randomised trials Twenty-one trials covered 2,041 people with type 2 diabetes. The analysis expressed its results per unit of intake, so the effect sizes are not reproduced on this page. All were small. Under the GRADE system the evidence rated low for BMI, moderate for HbA1c and high for LDL cholesterol. Scatter between trials ran above 90 per cent throughout, and the authors ask for very cautious reading [33].

Meta-analysis of randomised trials Eighteen trials covered 1,161 adults, mostly with liver disease. ALT was lower by 8.65 international units per litre, AST by 8.52 and gamma-GT by 8.80. Under the NutriGrade system the evidence rated moderate for ALT and AST and low for gamma-GT. These are laboratory values, not clinical outcomes [34].

Meta-analysis of randomised trials In women with overweight or obesity, fasting glucose fell by 2.93 milligrams per decilitre. Fasting insulin fell by 3.54 microunits per millilitre and the HOMA-IR index by 0.69. A companion analysis of ten trials found triglycerides lower by 8.01 milligrams per decilitre and total cholesterol by 7.85. HDL cholesterol was unchanged [35], [36].

Meta-analysis of randomised trials Six trials in 672 women with polycystic ovary syndrome found lower cholesterol, triglycerides, weight, BMI and waist measurements, all p below 0.05. Nothing in glucose metabolism changed significantly [37].

Dialysis and the heart

Randomised controlled trial The trial randomised 222 dialysis patients with low blood carnitine and analysed 148. The heart's ejection fraction rose by 5.43 per cent against a fall of 0.14 per cent in controls, p below 0.001. Left ventricular mass index fell by 8.89 grams per square metre. The trial was open-label with no dummy treatment [38].

Meta-analysis Twenty-seven trials in dialysis patients report large standardised differences for albumin, total protein, transferrin and prealbumin. All of these are laboratory markers, and the individual trials were mostly small [39].

Meta-analysis of controlled trials Thirteen trials covered 3,629 people after a heart attack. All-cause mortality was 27 per cent lower, odds ratio 0.73, p = 0.05. Ventricular arrhythmias were 65 per cent lower and angina 40 per cent lower. Heart failure and reinfarction did not change. Most of these trials predate modern reperfusion treatment [40].

Randomised controlled trial In 472 patients after a first anterior heart attack, the rise in ventricular volumes was smaller at 3, 6 and 12 months. Ejection fraction did not differ. Death and heart failure after discharge affected 14 of 233 against 23 of 239, which was not statistically significant [41].

Endpoints that were missed

Randomised controlled trial The follow-up trial enrolled 2,330 patients instead of the planned 4,000 and stopped early for slow recruitment. Death and heart failure at six months came to 9.2 against 10.5 per cent, p = 0.27. Only a secondary measure, mortality at day five, favoured treatment, hazard ratio 0.61, p = 0.041 [13].

The largest heart trial: death and heart failure at six months
L-Carnitinenot significant
9.2per cent of patients
Dummy treatmentp = 0.27
10.5per cent of patients

Randomised, double-blind trial in 2,330 patients after an anterior heart attack, stopped early. The difference was not statistically significant, p = 0.27. Source [13].

Phase 2 randomised trial The trial enrolled 250 adults with septic shock at 16 American centres. Organ failure scores after 48 hours fell by 1.27, 1.66 and 1.97 points across the three treatment arms, against 1.63 under dummy treatment. The chance that the highest arm was superior reached 0.78, below the pre-set threshold of 0.90.

Mortality at 28 days was 45.9 per cent under dummy treatment and 43.3 per cent in the highest arm [14].

Phase 3 randomised trial The trial gave acetyl-L-carnitine to 409 women on taxane chemotherapy. There was no benefit at 12 weeks and a significantly worse nerve damage score at 24 weeks, p = 0.01.

Severe neurotoxicity occurred eight times against once under dummy treatment. The authors describe it as the first study they know of in which a supplement increased this side effect [15].

A cancer guideline now advises against its use for that purpose because of a possibility of harm [42].

Umbrella review A review of 22 systematic reviews looked at chronic heart failure. It concluded that the benefits of L-carnitine and other supplements remain unclear. Coenzyme Q10 and tai chi reached moderate certainty [43].

Meta-analysis of randomised trials Eight fertility trials found better sperm motility and shape, but no change in sperm concentration. In the five trials that measured clinical pregnancy, the pregnancy rate did not change [44]. A separate trial in 60 men with poor sperm motility found the clearest improvement in those who started worst, and did not report pregnancies [45].

TMAO, the metabolite made from it

Human and animal study Gut bacteria break L-carnitine down into trimethylamine, which the liver oxidises into TMAO. In 2,595 people undergoing cardiac assessment, high blood carnitine predicted cardiovascular disease and future heart attack, stroke or death. That held only in those who also had high TMAO.

In mice, carnitine accelerated atherosclerosis, and suppressing the gut flora abolished the effect [46].

Human isotope study Forty meat eaters and 32 vegetarians or vegans were given labelled L-carnitine. Meat eaters produced more than twenty times as much labelled TMAO, p = 0.001. The decisive second step of the pathway is switched on by an omnivorous diet and by lasting supplement use. A single bacterium, Emergencia timonensis, carries it out [11].

Meta-analysis of prospective studies The pool covered 19 studies in 19,256 people with 3,315 events. High TMAO carried a relative risk of 1.62 for major cardiovascular events and 1.63 for death from any cause. For raised precursors, L-carnitine explicitly among them, the risk ran about 1.3 to 1.4 times higher [12].

Meta-analysis of prospective studies A second pool followed 26,167 people for a mean of 4.3 years. The hazard ratio was 1.91 for death, p below 0.0001, and 1.67 for major cardiac and cerebrovascular events. Each 10 micromoles per litre of TMAO added 7.6 per cent to relative mortality risk [47].

This is an association in humans and causation only in mice. It is nevertheless the single most important open question about taking L-carnitine for years [46], [12].

What is still unknown

  • Whether the TMAO produced by supplement use actually raises cardiovascular risk in people. No trial has ever tested that endpoint [11].
  • Whether the small weight difference means anything for health, given that it fades with time and appears only alongside lifestyle change [8], [26].
  • What long-term use does in healthy people above the amounts covered by the formal risk assessment [48].
  • Whether an injection does anything for weight at all. Not one controlled trial has tested it [21].
  • Whether the substance causes cancer over a lifetime. Long-term studies were never done [21].

Side effects and safety

L-Carnitine is generally well tolerated, and the American label lists no contraindications at all. That is a statement about approved use in patients, not a clean bill of health for anything anyone might do with it [21].

  • The frequency table comes from very sick people. The American label lists events at five per cent or more in dialysis patients, without judging cause. Headache reached 22 per cent against 16 under dummy treatment, high blood pressure 20 against 14, diarrhoea 16 against 19, vomiting 15 against 16. Injection-site reactions ran 33 per cent against 59 [21].
  • Severe allergic reactions are on the label. Anaphylaxis, swelling of the larynx and bronchospasm are listed under warnings, some occurring within minutes of an injection. Rash, hives and facial swelling are reported for the oral forms [21], [49].
  • Seizures have been reported after marketing. The label states that seizures have occurred after both oral and intravenous use. That includes patients with no pre-existing seizure disorder. In people who already had epilepsy, attacks became more frequent or more severe [21].
  • Metabolites build up when the kidneys are weak. The label warns that chronic high oral use in severe renal impairment can accumulate trimethylamine and TMAO. That applies on dialysis too. In six dialysis patients over twelve days, blood carnitine rose from 32.4 to 66.1 micromoles per litre. TMAO rose from 289.1 to 529.0, both p below 0.05 [21], [50].
  • A fishy body odour comes from the same chemistry. Trimethylamine is the compound behind the inherited condition that carries that name. The odour is listed as an adverse reaction [51], [21].
  • It interacts with warfarin. Rises in INR have been observed, and the label asks for monitoring after starting treatment [21].
  • Animal reproduction studies were unremarkable. Rats and rabbits showed no harm up to 3.8 times the human exposure adjusted for body surface. Adequate studies in pregnant women are missing [21].
  • Mutagenicity tests were negative, carcinogenicity was never tested. Three standard assays came back negative. No long-term cancer study exists [21].
  • Acute overdose has not been reported. The label records no case of toxicity from overdose and notes that carnitine is easily removed from the blood by dialysis. Lethal-dose testing in rats and mice put the fatal amount far above anything used in people. Large amounts by mouth cause diarrhoea [21].
  • The long-term safety literature is thin. A formal risk assessment derived an observed safe level for continuous supplement use, which this page does not reproduce. Higher amounts have been tested without harm, but the data do not support a firm statement about taking it for years [48].

Why this page lists no doses

L-Carnitine is an approved prescription medicine in the United States, the United Kingdom, Canada and Switzerland, and the injected form is prescription-only in Germany. Where a medicine is approved, its dosing belongs to the official product information and to the doctor or pharmacist handling it, not to a reference page.

The amounts used in the studies above were chosen for those studies, in patients with defined conditions or under laboratory control. None of them transfers to a healthy reader. This page therefore gives no amounts, strengths, schedules or instructions, in any direction.

Development and approval status

From a rare-disease medicine to a fat-burner drip

  1. 1985First American approvalTablets and oral solution approved on 27 December for primary systemic carnitine deficiency, ref [1]
  2. 1992The injection is approvedIntravenous solution approved on 16 December for inherited metabolic disorders and dialysis, ref [1]
  3. 1995Heart remodelling trial472 patients, smaller ventricular volumes, unchanged ejection fraction, ref [41]
  4. 2006The large heart trial misses its target2,330 patients, 9.2 against 10.5 per cent, p = 0.27, stopped early, ref [13]
  5. 2011Europe rejects the first claimsCholesterol, sperm, energy metabolism and pregnancy claims all turned down, ref [6]
  6. 2013The TMAO findingGut bacteria turn carnitine into a metabolite tied to atherosclerosis in mice, ref [46]
  7. 2016Required in infant formulaEuropean law sets a minimum content for infant formula, ref [52]
  8. 2018Europe rejects the fat metabolism claimNo cause and effect relationship established, ref [7]
  9. 2026Status as at 10 SeptemberPrescription medicine in four markets, free food ingredient by mouth in the European Union
MarketBy mouthAs a medicineInjection for weight
United StatesSupplementPrescriptionNot approved
United KingdomSupplementPrescriptionNot approved
CanadaSupplementPrescriptionNot approved
SwitzerlandSupplementPrescriptionNot approved
GermanyFreePrescriptionNot approved
European UnionPermittedNational onlyNot approved
AustraliaNot checkedNot checkedNot approved

The status was checked on 10 September 2026. Three points need spelling out.

Germany splits the substance in two. The prescription rules name the entry "L-Carnitin – zur parenteralen Anwendung –", so only the injected form needs a prescription and capsules do not [5]. Anyone injecting a vial bought abroad is using a prescription medicine without one.

The European Union has no centrally approved carnitine medicine; a full-text search of the agency's own list returned nothing, while a control search worked [53]. By contrast, food law expressly permits it as an ingredient [23]. Infant formula must contain at least 0.3 milligrams per 100 kilojoules, which is 1.2 milligrams per 100 kilocalories [52].

The Australian row is unverified. The poisons standard contains no carnitine entry, but the medicines register itself was unreachable on the day of checking [54].

In the United States, L-carnitine appears on none of the compounding lists, because it is part of an approved medicine already. Acetyl-L-carnitine does appear, in category 1, still under evaluation [55]. Neither is on the list of substances that may present significant safety risks [56].

American enforcement letters about carnitine target health claims made for supplements, not the substance itself [57]. For the wider picture see are peptides legal.

Anti-doping

L-Carnitine is not named on the 2026 prohibited list, and the catch-all clause for unapproved substances does not reach it. That clause requires the absence of any government approval for human therapeutic use, and four countries have approved it [16].

The route can still be a violation. Section M2.2 of the 2026 list prohibits, in its own words, “intravenous infusions and/or injections of more than a total of 100 mL per 12-hour period except for those legitimately received in the course of hospital treatments, surgical procedures or clinical diagnostic investigations”. A carnitine drip above that volume breaks the rule even though the substance itself is allowed [16].

The instructive contrast is meldonium, banned since 2016. It blocks carnitine synthesis and uptake and lowers muscle carnitine. What is prohibited is the carnitine-lowering drug, not carnitine [16], [58]. More context is at peptides banned in sport.

Compared with related peptides

SubstanceWhat it isStatusStrongest human evidence found here
L-CarnitineBetaine made by the body, carries fat into mitochondriaPrescription medicine in four markets; food ingredient by mouth1.21 kg less weight across 37 trials in 2,292 adults [9]
Acetyl-L-carnitineThe acetyl ester, studied mostly in the nervous systemUnder evaluation as a compounding substance in the United StatesWorse nerve damage than dummy treatment at 24 weeks in 409 women, p = 0.01 [15]
NAD+Coenzyme made by every cell, also not a peptideApproved nowhere for the uses marketedNo study comparing it with L-carnitine among the sources used here
GlutathioneTripeptide made by every cellMedicine in Japan and Italy; supplement elsewhereNo study comparing it with L-carnitine among the sources used here
SemaglutideGLP-1 receptor agonist, a true peptideApproved medicine for weight in many marketsNo study comparing it with L-carnitine among the sources used here
AOD-9604Fragment of growth hormone, marketed for fat lossApproved nowhereNo study comparing it with L-carnitine among the sources used here

The comparison that matters is with acetyl-L-carnitine, because the two are constantly treated as interchangeable. They are chemically related but regulated differently, and the largest trial of the acetyl form produced harm rather than benefit [15], [55].

The other four are in the table for a different reason. All are sold through the same shops and marketed with similar promises, and none has been compared with L-carnitine in any study used for this page.

Two of the six, L-carnitine and NAD+, are not peptides at all. They appear in this register because of where they are sold, not because of what they are [17].

Common misconceptions

  • "L-Carnitine, D-carnitine and DL-carnitine are the same thing." Only the L-form works. The D-form disturbs carnitine-dependent processes. That is why the medicine is defined as levocarnitine, with optical rotation between minus 29 and minus 32 degrees as a purity test [17], [21].
  • "If carnitine carries fat into the mitochondria, more of it burns more fat." That skips the decisive step. In well-nourished people the muscle store is not the limiting factor, and swallowing it does not raise that store. It rose by 21 per cent only under sustained high insulin over 24 weeks [10], [28].
  • "The injection works better because it skips poor absorption." The absorption gap is real. Supplement amounts deliver 14 to 18 per cent, and the largest oral amount tested as little as 5 per cent. What follows is a higher blood level that the kidney clears quickly, not a proven benefit. No controlled trial of intravenous carnitine for weight exists anywhere [59], [22], [14].
  • "The prescription product is the same as the tub from the sports shop." The molecule is identical; the two worlds are not. One is an approved medicine with product information, batch testing and adverse event reporting. The other is a food with no approval procedure and, in Europe, not a single permitted health claim [1], [7].
  • "L-Carnitine is a peptide." It is a single small molecule of 161.20 g/mol with no peptide bond. Being built from lysine and methionine makes it no more a peptide than adrenaline, which is built from tyrosine [17], [18].
  • "It is not on the doping list, so anything goes in sport." The substance is allowed; the drip may not be. Infusions above 100 millilitres per 12 hours are prohibited whatever they contain, and supplement contamination remains the athlete's own responsibility under strict liability [16].
  • "Carnitine comes from meat, so taking it can only be healthy." This is exactly where the most interesting recent finding sits. Gut bacteria convert it into a metabolite linked in large prospective studies to more cardiac events and higher mortality. Lasting intake switches that pathway on [11], [12].

Frequently asked questions

Is L-carnitine a peptide?

No. L-Carnitine is a single small molecule of 161.20 g/mol with no peptide bond and no amino acid sequence. Chemists classify it as a betaine. It appears in this peptide register only because it is sold as an injection alongside research peptides.

Is L-carnitine a prescription medicine?

In four countries, yes. The United States approved it on 27 December 1985 and the injection on 16 December 1992, and the United Kingdom, Canada and Switzerland classify it as prescription-only. The approved uses are inherited metabolic disorders causing carnitine deficiency, and carnitine deficiency in dialysis patients. Nowhere is it approved for weight, fat burning or sport.

Why does this page list no L-carnitine doses?

Because levocarnitine is an approved prescription medicine in four countries. Where a medicine is approved, the dosing belongs to its official product information and to a doctor or pharmacist. The amounts used in the studies described here were chosen for those studies, in defined patient groups. None of them transfers to a healthy reader.

How much weight did the L-carnitine trials show?

About one kilogram. Nine trials in 911 adults found 1.33 kg less than control, and 37 trials in 2,292 adults found 1.21 kg. Two further pooled analyses landed at 1.13 and 1.11 kg. The effect shrank significantly the longer trials ran, p = 0.002, and appeared only alongside lifestyle change.

Does L-carnitine burn fat?

The transport role is real, but the chain of reasoning breaks at the next link. In well-nourished people the muscle store is not what limits fat burning. Swallowing carnitine does not raise it either. Muscle content rose by 21 per cent only under high insulin levels sustained over 24 weeks. Europe's food safety authority rejected the fat metabolism claim in 2018.

What is the TMAO problem with L-carnitine?

Gut bacteria convert L-carnitine into trimethylamine, which the liver oxidises into TMAO. Meat eaters produced more than twenty times as much labelled TMAO as vegetarians and vegans, p = 0.001, and lasting intake switches the pathway on. High TMAO carried a relative risk of 1.62 for major cardiac events across 19 studies in 19,256 people. That is an association in humans, with causation shown only in mice.

Is L-carnitine banned in sport?

The substance is not named on the 2026 prohibited list, and the catch-all clause does not reach it, because four countries have approved it as a medicine. The method can still be prohibited: infusions and injections above 100 millilitres per 12 hours are banned outside hospital care. Meldonium, which lowers muscle carnitine, has been banned since 2016.

Only on prescription. German prescription law names the entry "L-Carnitin – zur parenteralen Anwendung –", so the injected form is prescription-only while capsules are freely sold. Injecting a vial bought abroad means using a prescription medicine without a prescription, and for a purpose approved nowhere.

What is the difference between L-carnitine and acetyl-L-carnitine?

They are related but not interchangeable. Acetyl-L-carnitine is an ester studied mostly in the nervous system. In the United States it is still under evaluation as a compounding substance, while levocarnitine is an approved medicine. In the largest trial of the acetyl form, 409 women on chemotherapy had significantly worse nerve damage than under dummy treatment at 24 weeks, p = 0.01.

Does L-carnitine have side effects?

The label lists no contraindications, but it does list several warnings. Severe allergic reactions including anaphylaxis have occurred, sometimes within minutes of an injection. Seizures have been reported after marketing, after both oral and intravenous use, in people with and without a pre-existing seizure disorder. A fishy body odour and stomach complaints are the common ones. INR should be watched in people taking warfarin.

Sources

  1. U.S. Food and Drug Administration. Drugs@FDA, query via the openFDA interface for the generic name “levocarnitine”, 10 September 2026. Twelve approvals, including NDA 018948 (Carnitor tablets and oral solution, original approval 27 December 1985, priority review, Type 1 new molecular entity), NDA 019257 (10 April 1986) and NDA 020182 (injection, 16 December 1992), sponsor Leadiant Biosciences, Inc. https://api.fda.gov/drug/drugsfda.json
  2. electronic medicines compendium. Levocarnitine Paediatric 30% Oral Solution alcohol free & sugar free, Aspire Pharma Ltd, PL 35533/0268, Summary of Product Characteristics, first authorised 16 June 2025, text revised 28 April 2026, legal status prescription only medicine. Retrieved 10 September 2026. https://www.medicines.org.uk/emc/product/9538/smpc
  3. Health Canada. Drug Product Database, public API, queried 10 September 2026: DIN 02144328, 02144336, 02144344, 02492105, 02562685 and 02566958, all schedule prescription. https://health-products.canada.ca/api/drug/
  4. Swissmedic. List of authorised preparations (packages file), evaluated 10 September 2026: Carnitene injection solution (authorisation 43716), syrup (47597), oral solution (48508) and chewable tablets (48509), Alfasigma Schweiz AG, ATC A16AA01, dispensing category B.
  5. Arzneimittelverschreibungsverordnung (German prescription regulation), Annex 1 to section 1 no. 1 and section 5, full text from gesetze-im-internet.de, checked 10 September 2026. Entry: “L-Carnitin – zur parenteralen Anwendung –”.
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  7. EFSA Panel on Dietetic Products, Nutrition and Allergies (2018). L-carnitine and contribution to normal lipid metabolism: evaluation of a health claim pursuant to Article 13(5) of Regulation (EC) No 1924/2006. EFSA Journal 2018;16(1):5137. Adopted 13 December 2017, question EFSA-Q-2017-00564. DOI 10.2903/j.efsa.2018.5137. PMID 32625683.
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  11. Koeth RA, Lam-Galvez BR, Kirsop J, Wang Z, Levison BS, Gu X et al. (2019). l-Carnitine in omnivorous diets induces an atherogenic gut microbial pathway in humans. J Clin Invest 129(1):373-387. PMID 30530985. ClinicalTrials.gov NCT01731236.
  12. Heianza Y, Ma W, Manson JE, Rexrode KM, Qi L (2017). Gut microbiota metabolites and risk of major adverse cardiovascular disease events and death: a systematic review and meta-analysis of prospective studies. J Am Heart Assoc 6(7):e004947. PMID 28663251.
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  15. Hershman DL, Unger JM, Crew KD, Minasian LM, Awad D, Moinpour CM et al. (2013). Randomized double-blind placebo-controlled trial of acetyl-L-carnitine for the prevention of taxane-induced neuropathy in women undergoing adjuvant breast cancer therapy. J Clin Oncol 31(20):2627-2633. PMID 23733756. ClinicalTrials.gov NCT00775645 (SWOG S0715).
  16. World Anti-Doping Agency. The 2026 Prohibited List, International Standard. Sections S0 (non-approved substances), M2.2 (infusions above 100 mL per 12 hours) and S4.4.3 (meldonium). Full text checked 10 September 2026; a search for “carnit” returned no match.
  17. PubChem, Compound CID 10917 (levocarnitine), PUG-REST query 10 September 2026: C7H15NO3, 161.20 g/mol, exact mass 161.10519334, InChIKey PHIQHXFUZVPYII-ZCFIWIBFSA-N, IUPAC name (3R)-3-hydroxy-4-(trimethylazaniumyl)butanoate, CAS 541-15-1, UNII 0G389FZZ9M.
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  20. WHO Collaborating Centre for Drug Statistics Methodology. ATC/DDD Index, code A16AA01 levocarnitine, group A16AA “Amino acids and derivatives”, retrieved 10 September 2026. https://atcddd.fhi.no/atc_ddd_index/?code=A16AA01
  21. DailyMed (U.S. National Library of Medicine). CARNITOR (levocarnitine) Injection, Structured Product Label, setid cf801cc4-775e-433d-9d32-e5d9a98981d3, Leadiant Biosciences, Inc. Full text retrieved 10 September 2026.
  22. Rebouche CJ (2004). Kinetics, pharmacokinetics, and regulation of L-carnitine and acetyl-L-carnitine metabolism. Ann N Y Acad Sci 1033:30-41. PMID 15591001.
  23. Commission Regulation (EC) No 953/2009 of 13 October 2009 on substances that may be added for specific nutritional purposes in foods for particular nutritional uses. OJ L 269, 14.10.2009, p. 9. Annex, category 4 “Carnitine and taurine”. CELEX 32009R0953, full text retrieved 10 September 2026.
  24. Wikidata, entity Q20735709 (L-carnitine), Special:EntityData, retrieved 10 September 2026: DrugBank DB00583, ChEMBL CHEMBL1149, ChEBI 16347, KEGG D02176, RxNorm 42955, DSSTox DTXSID4023208.
  25. Stephens FB, Constantin-Teodosiu D, Laithwaite D, Simpson EJ, Greenhaff PL (2006). An acute increase in skeletal muscle carnitine content alters fuel metabolism in resting human skeletal muscle. J Clin Endocrinol Metab 91(12):5013-5018. PMID 16984983.
  26. Askarpour M, Hadi A, Miraghajani M, Symonds ME, Sheikhi A, Ghaedi E (2020). Beneficial effects of l-carnitine supplementation for weight management in overweight and obese adults: an updated systematic review and dose-response meta-analysis of randomised controlled trials. Pharmacol Res 151:104554. PMID 31743774.
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  28. Stephens FB, Wall BT, Marimuthu K, Shannon CE, Constantin-Teodosiu D, Macdonald IA, Greenhaff PL (2013). Skeletal muscle carnitine loading increases energy expenditure, modulates fuel metabolism gene networks and prevents body fat accumulation in humans. J Physiol 591(18):4655-4666. PMID 23818692.
  29. Chee C, Shannon CE, Burns A, Selby AL, Wilkinson D, Smith K, Greenhaff PL, Stephens FB (2021). Increasing skeletal muscle carnitine content in older individuals increases whole-body fat oxidation during moderate-intensity exercise. Aging Cell 20(2):e13303. PMID 33464721.
  30. Yarizadh H, Shab-Bidar S, Zamani B, Vanani AN, Baharlooi H, Djafarian K (2020). The effect of L-carnitine supplementation on exercise-induced muscle damage: a systematic review and meta-analysis of randomized clinical trials. J Am Coll Nutr 39(5):457-468. PMID 32154768.
  31. Talebi S et al. (2024). Nutritional interventions for exercise-induced muscle damage: an umbrella review of systematic reviews and meta-analyses of randomised trials. Nutr Rev 82(3):331-349. PMID 37460208.
  32. Mielgo-Ayuso J, Pietrantonio L, Viribay A, Calleja-González J, González-Bernal J, Fernández-Lázaro D (2021). Effect of acute and chronic oral l-carnitine supplementation on exercise performance based on the exercise intensity: a systematic review. Nutrients 13(12):4359. PMID 34959912.
  33. Mirrafiei A, Jayedi A, Shab-Bidar S (2024). The effects of L-carnitine supplementation on weight loss, glycemic control, and cardiovascular risk factors in patients with type 2 diabetes: a systematic review and dose-response meta-analysis of randomized controlled trials. Clin Ther 46(5):404-410. PMID 38594107.
  34. Pirmadah F, Ramezani-Jolfaie N, Mohammadi M, Talenezhad N, Clark CCT, Salehi-Abargouei A (2020). Does L-carnitine supplementation affect serum levels of enzymes mainly produced by liver? A systematic review and meta-analysis of randomized controlled clinical trials. Eur J Nutr 59(5):1767-1783. PMID 31385062.
  35. Liu H et al. (2025). Effects of carnitine supplementation on glycemic markers in women with overweight and obesity: a systematic review and meta-analysis of randomized controlled trials. Diabetes Res Clin Pract 231:112981. PMID 41177307.
  36. Yu Y et al. (2026). Impact of L-carnitine supplementation on lipid profile parameters in overweight and obese women: a systematic review and meta-analysis of randomized controlled trials. Nutr Metab (Lond). PMID 42332819.
  37. Liao D et al. (2022). Clinical evidence of the effects of carnitine supplementation on body weight, glycemic control and serum lipids in women with polycystic ovary syndrome: a systematic review and meta-analysis. Gynecol Endocrinol 38(1):2-8. PMID 34633275.
  38. Higuchi T, Abe M, Yamazaki T, Okawa E, Ando H, Hotta S et al. (2016). Levocarnitine improves cardiac function in hemodialysis patients with left ventricular hypertrophy: a randomized controlled trial. Am J Kidney Dis 67(2):260-270. PMID 26508680.
  39. Zhou J, Liu J, Lin Q, Shi L, Zeng Z, Guan L et al. (2020). The efficacy of L-carnitine in improving malnutrition in patients on maintenance hemodialysis: a meta-analysis. Biosci Rep 40(6):BSR20192463. PMID 32490516.
  40. DiNicolantonio JJ, Lavie CJ, Fares H, Menezes AR, O'Keefe JH (2013). L-carnitine in the secondary prevention of cardiovascular disease: systematic review and meta-analysis. Mayo Clin Proc 88(6):544-551. PMID 23597877.
  41. Iliceto S, Scrutinio D, Bruzzi P, D'Ambrosio G, Boni L, Di Biase M et al. (1995). Effects of L-carnitine administration on left ventricular remodeling after acute anterior myocardial infarction: the CEDIM trial. J Am Coll Cardiol 26(2):380-387. PMID 7608438.
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  44. Khaw SC, Wong ZZ, Anderson R, Martins da Silva S (2020). l-carnitine and l-acetylcarnitine supplementation for idiopathic male infertility. Reprod Fertil 1(1):67-81. PMID 35128424.
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  55. U.S. Food and Drug Administration. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the FD&C Act, as at 14 May 2026. Acetyl-L-carnitine appears in category 1; L-carnitine itself is not listed. https://www.fda.gov/media/94155/download
  56. U.S. Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks, page as at 22 April 2026. Full text searched for “carnitin” on 10 September 2026, no match, with a working control search.
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  58. Porter C, Constantin-Teodosiu D, Constantin D, Leighton B, Poucher SM, Greenhaff PL (2017). Muscle carnitine availability plays a central role in regulating fuel metabolism in the rodent. J Physiol 595(17):5765-5780. PMID 28605113.
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Cite this page

myPeptides Research & Editing. "L-Carnitine: what the studies show, status and safety." mypep.app, 10 September 2026. https://mypep.app/peptides/l-carnitine

The status of every market was checked against the named authority on 10 September 2026. Where a check failed or a source was missing, the page says so rather than filling the gap.

VersionDateChange
1.010 September 2026Initial publication

Identifiers

IdentifierValue
CAS number541-15-1
PubChem CID10917
UNII0G389FZZ9M
InChIKeyPHIQHXFUZVPYII-ZCFIWIBFSA-N
DrugBankDB00583
ChEMBLCHEMBL1149
WikidataQ20735709
Molecular formulaC7H15NO3
Molecular weight161.2

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Last reviewed: September 2026

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