Ipamorelin vs Sermorelin: differences, evidence and safety

Answer first

Both make the pituitary gland release the body's own growth hormone, through different receptors. Sermorelin copies the front part of the natural releasing hormone (GHRH) and was an approved American medicine until 2009. Ipamorelin mimics the hunger hormone ghrelin, failed its only published patient trial and appears in no approval register reviewed. The sources reviewed contain no direct comparison.

At a glance

How they work

Neither substance is growth hormone. Both act one step earlier. They prompt the pituitary gland, a small gland at the base of the brain, to release the growth hormone it already holds. The difference lies in which switch they press.

Ipamorelin is a lab-made peptide of just five building blocks, first described by Novo Nordisk in 1998 ^[1].

• It docks onto the receptor for the hunger hormone ghrelin. Blocking experiments showed that its effect runs through that receptor and not through the receptor for the natural releasing hormone ^[1].
• In healthy men, a single infusion into a vein produced one peak of growth hormone after about 40 minutes (0.67 hours). The final phase of its stay in the blood lasted about 2 hours ^[2].
• In pigs that were awake, the stress hormone cortisol and its trigger hormone did not rise noticeably, even far above the effective dose. No test of this "selectivity" in people could be found in the sources reviewed ^[1], ^[3].
• In mice it raised the proportion of body fat and made the animals eat more, while growth hormone itself lowered body fat ^[4].

Sermorelin is a lab-made copy of the first 29 building blocks of growth hormone releasing hormone (GHRH). The natural hormone is 44 building blocks long, and this fragment is the shortest piece that keeps its full activity ^[5].

• It docks onto the GHRH receptor on the growth hormone cells of the pituitary and switches them on ^[5], ^[6].
• Growth hormone then comes out in bursts, as it normally does. Somatostatin, the body's own brake on this circuit, keeps working ^[5].
• In older adults, the release of growth hormone began within 10 minutes of an injection under the skin and lasted about two hours ^[7].
• The peptide itself leaves the blood fast. Its half-life is roughly 10 to 20 minutes, because the kidneys filter it out and enzymes clip its front end ^[8]. Under a steady drip into a vein in 10 healthy men, the half-life was 4.3 ± 1.4 minutes ^[9].

The core difference is the door, not the room. Both end at the same pituitary cells, but sermorelin uses the GHRH receptor and ipamorelin the ghrelin receptor. A 2026 review therefore places them in different families, and the anti-doping list files them under different headings ^[10], ^[11].

Both depend on a pituitary gland that works. Ipamorelin cannot stand in for growth hormone ^[3], and sermorelin's action passes through the same gland and its brake ^[5].

What the studies show

No study that compares ipamorelin and sermorelin directly could be found in the published record reviewed for this page. The closest link is the 1998 pig work. It measured ipamorelin against the natural releasing hormone, of which sermorelin is a fragment, not against sermorelin itself ^[1].

What follows are separate studies of each substance. They involved different people, different questions and different lengths of treatment. The numbers cannot be set against each other to decide which works better.

Ipamorelin: growth hormone in healthy men

Phase 1 Forty-eight healthy men took part, and 40 of them were analysed across five dose levels. The more they received, the higher their growth hormone climbed. It peaked after about 40 minutes and fell back to barely measurable levels within 6 hours ^[2].

That is the entire published record of what the peptide does in people. It measured a marker in the blood after a single infusion. Nothing a patient would notice was measured ^[3].

Ipamorelin: the bowel-surgery trial

Phase 2 RCT Patients had just had part of their bowel removed. The trial asked how long it took until they could keep down a solid meal. Among 117 adults, the median, or middle value, was 25.3 hours on ipamorelin against 32.6 hours on placebo.

That gap was small enough to be chance (p = 0.15). No other measure differed meaningfully ^[12].

Development stopped after this result ^[3]. A second mid-stage trial with 320 adults finished in May 2014, and no published results for it could be found in the sources reviewed ^[13]. In the studies reviewed, nobody received ipamorelin for longer than 7 days ^[12].

Ipamorelin: animal findings

Animal data In rats after abdominal surgery, the share of a meal left in the stomach fell from 78 to 52 per cent, against 44 per cent in animals that had not been operated on ^[14]. The human trial failed all the same ^[12].

Animal data Over 15 days in adult female rats, the shin bone grew slightly faster, from 42 to 52 thousandths of a millimetre a day. After those 15 days, a test injection released slightly less growth hormone than at the start (P < 0.03), a sign of tolerance ^[15].

Sermorelin: growth in children with growth hormone deficiency

Open-label multicentre study The study behind the 1997 American approval enrolled 110 previously untreated children before puberty, and 86 entered the efficacy analysis. Average growth speed rose from 4.1 ± 0.9 centimetres a year to 8.0 ± 1.5 after six months.

After twelve months it settled at 7.2 ± 1.3. At six months, 74 per cent counted as good responders. There was no comparison group ^[16].

Open treatment series An earlier series treated 18 children, 14 of whom had already had growth hormone. Growth speed increased in 12 of the 18. Four of the 14 previously treated children grew more slowly on sermorelin, for reasons the authors could not explain ^[17].

Sermorelin: where it fell short of growth hormone

Narrative review A 1999 review compared published studies indirectly. It concluded that growth speed rose less under sermorelin than under growth hormone itself. The review names no head-to-head trial and reports no final adult height for the treated children ^[5].

Sermorelin: hormone levels in older adults

Randomised crossover series Nine healthy young men, average age 26.2 years, were compared with 10 healthy older men, average age 68.0 years. The older men received two dose levels in random order, two weeks each.

Only the higher level raised average growth hormone across 24 hours (p < 0.001). It also raised IGF-1 (p < 0.005), a growth messenger made mainly in the liver. These are laboratory values, not measures of strength or wellbeing ^[18].

Placebo-controlled study Ten women and nine men aged 55 to 71 had four weeks of placebo, then 16 weeks of active treatment.

Growth hormone secretion at night rose by 107 per cent in the men and 70 per cent in the women (p < 0.05). IGF-1 rose by 28 per cent (p < 0.001). No clinical benefit was measured ^[7], ^[19].

Sermorelin: the study that measured strength

Open treatment series Eleven healthy men aged 64 to 76 were treated for six weeks. Night-time growth hormone release rose, but IGF-1 did not change.

Of six strength measures, two improved: the upright row (p < 0.02) and the shoulder press (p < 0.04). Weight, body fat, muscle tissue, blood sugar and blood fats stayed where they were ^[20].

Safety

The two safety records are thin in different ways. Sermorelin's official product information is no longer publicly available, so no table of side-effect frequencies can be quoted ^[21]. For ipamorelin, human safety data come from one analysis of 114 participants and two side-effect reports ^[3]. Neither gap is a ranking of risk.

Ipamorelin, from the bowel-surgery trial, against placebo ^[12], ^[3]:

• Raised blood sugar at discharge affected 14.3 per cent against 8.6 per cent.
• Low potassium in the blood affected 12.5 per cent against 3.4 per cent.
• Trouble sleeping affected 10.7 per cent against 5.2 per cent.
• Serious events occurred in 10 of 56 participants, or 17.9 per cent, against 9 of 58 on placebo (15.5 per cent). Most began after treatment had ended.

Two people in the ipamorelin group died after the surgical join in their bowel leaked. The FDA writes that it is unclear whether the deaths had anything to do with ipamorelin ^[3]. It still cites them as one reason for filing the substance among possible safety risks for compounding ^[22].

No test of ipamorelin for damage to genetic material, harm to fertility or an unborn child, or cancer could be found in the sources reviewed ^[3]. They contain no safety data at all for injection under the skin, the route used outside trials ^[3].

Sermorelin, from the clinical record:

• Brief facial flushing and pain at the injection site were the most frequently reported events. The review that reports them gives no percentages ^[5].
• Antibodies against the hormone appeared in 14 of 18 children in the 1987 series, with no visible effect on growth ^[17].
• Slower growth in four of 14 previously treated children is the most concrete harm signal in the record. The study did not establish its cause ^[17].
• Fasting blood sugar, the insulin response and blood fats stayed unchanged in both studies in older adults ^[18], ^[20].

Formal contraindications for sermorelin cannot be stated, because no valid product information sheet could be found in the sources reviewed ^[21]. The sources reviewed contain no data on pregnancy, breastfeeding, or impaired kidney or liver function. Reviews of this class of peptides describe rises in prolactin and cortisol, disturbed blood sugar, fluid retention, and muscle and joint pain ^[11], ^[23].

Regulators have also looked at both substances as compounding ingredients. An FDA advisory committee voted 0 in favour and 12 against allowing pharmacies to compound ipamorelin ^[24]. Sermorelin appears on none of the American category lists for compounding and on no list of substances judged to raise significant safety risks ^[25], ^[26].

In the United States, sermorelin is dispensed only as a compounded preparation on a doctor's order. Such preparations undergo no regulatory review of safety, effectiveness or manufacturing quality ^[27]. Material bought outside a pharmacy, for either substance, has unverified composition, strength and purity.

Why this page lists no doses. Sermorelin is prescription-only by name in Germany and Australia. It was a prescription medicine wherever it was ever sold. Choosing an amount is a matter for a doctor, so this page reports what the studies measured for both substances without repeating the amounts used.

Legal status

Sermorelin held American approvals from 28 December 1990, as a diagnostic test, and from 26 September 1997, for children with growth hormone deficiency. Its maker stopped selling both in 2008 and asked for their withdrawal, effective 18 June 2009 ^[28], ^[29]. In March 2013 the regulator found that neither was withdrawn for safety or effectiveness reasons ^[30]. None of the registers reviewed for this page lists a current licence for it, but Germany and Australia name it as prescription-only ^[31], ^[32]. None of those registers lists an approval for ipamorelin, and in Australia possessing it without authority is an offence ^[33]. Both are banned in sport at all times under section S2.2.4 of the 2026 Prohibited List ^[10]. More at peptides banned in sport. Status as of 6 and 10 September 2026.

Used together?

The peptide directory under blends lists no product that combines ipamorelin and sermorelin. Its ipamorelin blends pair the peptide with other substances, such as CJC-1295 or tesamorelin.

No study of ipamorelin and sermorelin given together could be found in the ipamorelin or sermorelin monographs or in their sources.

The FDA record holds one side-effect report involving ipamorelin mixed with a second peptide. Because of the mixture, it was impossible to say what caused what ^[3]. CJC-1295 is built on the same backbone as sermorelin. For its pairing with ipamorelin, no clinical study testing the two together could be found in these sources ^[3], ^[34].

Frequently asked questions

Which is better, ipamorelin or sermorelin?

The studies cannot answer that, because no trial comparing the two could be found in the sources reviewed for this page. In 110 children with growth hormone deficiency, sermorelin raised average growth speed from 4.1 to 8.0 centimetres a year after six months. That study had no comparison group. Ipamorelin was tested in 117 adults after bowel surgery, on a different question, and missed its main goal.

Is ipamorelin or sermorelin safer?

No study putting the two side by side could be found in the sources reviewed for this page, so the data give no answer. For sermorelin, no current product information sheet turned up in that review. The most frequently reported events were brief facial flushing and pain at the injection site. For ipamorelin, the human safety data come from one analysis of 114 participants, and the sources reviewed report no results for many standard safety tests.

What is the difference between ipamorelin and sermorelin?

Both prompt the pituitary gland to release the body's own growth hormone. Sermorelin is the first 29 building blocks of the natural releasing hormone and uses that hormone's receptor. Ipamorelin has five building blocks and acts on the receptor for the hunger hormone ghrelin. Sermorelin was once an approved medicine, while work on ipamorelin stopped in 2014.

Can ipamorelin and sermorelin be taken together?

No study of the two given together could be found in the sources behind this page. The peptide directory lists no blend that contains both. Combining them would change nothing about their status in sport, where both are banned at all times.

Are ipamorelin and sermorelin approved medicines?

Neither is approved today. Sermorelin's American approvals from 1990 and 1997 ended on 18 June 2009 at the maker's request, after it stopped selling both products in 2008. None of the registers reviewed for this page lists an approval for ipamorelin. Germany and Australia name sermorelin as prescription-only, and in Australia possessing ipamorelin without authority is an offence.

Why was sermorelin withdrawn and ipamorelin dropped?

For different reasons. In March 2013 the American regulator determined that neither sermorelin product was withdrawn for reasons of safety or effectiveness. The withdrawal came from the maker, after sermorelin produced less growth in children than growth hormone and never found a market. Ipamorelin was dropped after its published trial after bowel surgery failed on its main question.

Are ipamorelin and sermorelin banned in sport?

Yes, both of them, at all times, in and out of competition. Section S2.2.4 of the 2026 Prohibited List names sermorelin among the copies of the natural releasing hormone and ipamorelin among the growth hormone secretagogues. Both count as non-specified substances, the stricter category.

How long do ipamorelin and sermorelin stay in the body?

Sermorelin leaves the blood within minutes, with a half-life of roughly 10 to 20 minutes. For ipamorelin, the final phase lasted about 2 hours after an infusion into a vein, in one study of healthy men. The figures come from different studies and methods, so they are not a like-for-like comparison.