Ipamorelin vs Tesamorelin: differences, evidence and safety

Answer first

Both make the pituitary gland release the body's own growth hormone, but through different receptors. Tesamorelin copies the natural releasing hormone (GHRH) and is a prescription medicine in the United States. Ipamorelin mimics the hunger hormone ghrelin, failed its only published patient trial and is approved nowhere. No direct comparison of the two could be found in the sources reviewed.

At a glance

How they work

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

Tesamorelin is a laboratory-made copy of growth hormone releasing hormone (GHRH), the signal the brain normally sends to the pituitary ^[1].

• It is a chain of 44 amino acid building blocks, the full natural sequence. A short six-carbon chain (a hexenoyl group) is attached at the front end. That addition slows the breakdown that clears the natural hormone within minutes ^[1].
• It binds to the GHRH receptors on the pituitary about as strongly as the natural hormone. Growth hormone is then released in the usual pulses ^[1].
• In patients it raised IGF-1, a growth messenger made mainly in the liver, and its carrier protein IGFBP-3. Thyroid and stress hormones did not shift meaningfully in the approval trials ^[1].
• It is cleared fast. The half-life is about 11 minutes in healthy adults, and the peak level arrives after a median of 0.15 hours, roughly 9 minutes ^[1].

Ipamorelin is a lab-made peptide of just five building blocks, first described by Novo Nordisk in 1998 ^[2].

• It docks onto the receptor for the hunger hormone ghrelin. Blocking experiments showed that its effect runs through that receptor and not through the GHRH receptor ^[2].
• 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 ^[3].
• In pigs that were awake, the stress hormone cortisol and its trigger hormone did not rise, even far above the effective dose. No check of this "selectivity" in people could be found in the sources reviewed ^[2], ^[4].
• In mice it raised the proportion of body fat and made the animals eat more, while growth hormone itself lowered body fat ^[5].

The core difference is the door, not the room. Both end at the same pituitary cells, but tesamorelin uses the GHRH receptor and ipamorelin the ghrelin receptor. Two 2026 reviews therefore place them in different families ^[6], ^[7].

Both need a working pituitary. Ipamorelin cannot stand in for growth hormone ^[4], and tesamorelin's label rules it out when the brain–pituitary link is disrupted ^[1].

What the studies show

No study that compares ipamorelin and tesamorelin directly could be found in the published record reviewed for this page. The closest link is not a head-to-head test. In the 1998 pig work, the stress hormones stayed at the level seen with the natural releasing hormone that tesamorelin copies ^[2]. Tesamorelin itself was not part of that study.

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.

Tesamorelin: deep belly fat in HIV

Phase 3 RCT The first approval trial randomised 412 adults with HIV and lipodystrophy for 26 weeks. Lipodystrophy is a condition in which body fat is redistributed. The deep fat around the organs fell by 15.2 per cent on treatment and rose by 5.0 per cent on placebo (p < 0.001) ^[8].

The label puts the difference at 31 square centimetres, or 20 per cent ^[1].

Phase 3 RCT A second trial followed 404 adults for six months. Deep belly fat fell by 10.9 per cent, against 0.6 per cent on placebo (p < 0.0001). Fat on the arms and legs, and the fat just under the skin of the belly, did not change ^[9].

Body weight did not move in either trial, changing by −0.4 kg and +0.5 kg, neither different from placebo. The label states that the drug is not for weight loss ^[1]. Pooling five randomised trials, the average difference against placebo was 27.71 square centimetres of visceral fat ^[10].

Tesamorelin: what happens after stopping

Phase 3 RCT In the extension phase, 263 participants were randomised again for a further 26 weeks. Those who stayed on treatment held the reduction at 18 per cent below their starting point at 52 weeks. Those switched to placebo lost the gains of the previous six months, and the deep fat accumulated again ^[11].

Tesamorelin: liver fat and thinking

RCT One trial enrolled 61 people with HIV whose liver fat was at least 5 per cent. Twelve months of treatment lowered it by 4.1 percentage points more than placebo (p = 0.018). After a year, 35 per cent of the treated group were below the 5 per cent threshold, against 4 per cent on placebo ^[12].

Phase 2 RCT An academic trial treated 152 adults aged 55 to 87, average age 68, for 20 weeks. It found a favourable overall effect on thinking skills (p = 0.03), mainly in planning and mental flexibility.

Side effects were reported by 68 per cent on treatment, against 36 per cent on placebo ^[13]. No regulator has approved tesamorelin for anything to do with memory.

Tesamorelin: where the trials fell short

Phase 2 RCT In 73 people with HIV and abdominal obesity, there was no cognitive advantage over the comparison group (p = 0.673). The trial was open-label, meaning everyone knew who got what, and its authors call it underpowered ^[14].

Phase 2 RCT The trial enrolled 53 adults who already had type 2 diabetes. Twelve weeks of treatment changed nothing measurable in their insulin response, fasting glucose or long-term blood sugar ^[15].

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 ^[3].

Nothing more on what the peptide does in people could be found in the published record reviewed for this page. It measured a marker in the blood after a single dose. Nothing a patient would notice was measured ^[4].

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 ^[16].

Development stopped after this result ^[4]. A second mid-stage trial with 320 adults finished in May 2014, and the trial registry lists no results for it ^[17]. No study giving ipamorelin for longer than 7 days could be found in the sources reviewed ^[16].

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 ^[18].

In adult female rats, the shin bone grew slightly faster over 15 days, from 42 to 52 thousandths of a millimetre a day ^[19]. The gut effect in rats did not carry over to the human trial ^[16].

Safety

The two safety records differ mainly in how much is known. Tesamorelin has an official American product information built on its approval trials. For ipamorelin, human safety data come from one analysis of 114 participants and two side-effect reports ^[4]. That difference in data is not a ranking of risk.

Tesamorelin, from the product information ^[1]:

• Injection-site reactions such as redness, itching and pain affected 17 per cent against 6 per cent on placebo over the first 26 weeks.
• Joint pain affected 13 per cent against 11 per cent, and muscle pain 6 per cent against 2 per cent.
• Swelling of the ankles and feet affected 6 per cent against 2 per cent, and tingling 5 per cent against 2 per cent. The label links both to fluid retention.
• Long-term blood sugar reached 6.5 per cent or more in 5 per cent of treated participants against 1 per cent on placebo.
• Allergic reactions affected 4 per cent, and antibodies against the drug appeared in 50 per cent at 26 weeks.

The label rules tesamorelin out in four situations: an active cancer, a disrupted link between brain and pituitary, a known allergy, and pregnancy ^[1].

Ipamorelin, from the bowel-surgery trial ^[4], ^[16]:

• Raised blood sugar at discharge affected 14.3 per cent against 8.6 per cent on placebo.
• 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 17.9 per cent against 15.5 per cent, most of them 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 ^[4]. It still cites them as one reason for filing the substance among possible safety risks for compounding ^[20].

The FDA review lists no tests of whether ipamorelin damages genetic material, harms fertility or causes cancer ^[4]. The FDA also points to the warnings on approved growth hormone products, which cover tumours, blood sugar problems and water retention ^[4].

Why this page lists no doses. Tesamorelin is prescription-only in the one market where it is approved. Choosing an amount is a matter for the official product information and the prescribing doctor. This page therefore reports what the studies measured for both substances without repeating the amounts used.

Legal status

Tesamorelin has been prescription-only in the United States since 10 November 2010. Its only approved use is excess belly fat in adults with HIV and lipodystrophy ^[21]. The European application was withdrawn on 21 June 2012 ^[22], and the Canadian product has been cancelled since 30 September 2022 ^[23]. Ipamorelin is approved nowhere. In Australia it is prescription-only, and possessing it without authority is an offence ^[24]. An FDA advisory committee voted 0 in favour and 12 against its use in pharmacy compounding ^[25]. Both are banned in sport at all times under section S2.2.4 of the 2026 Prohibited List ^[26], as explained under peptides banned in sport. The monographs were checked on 6 and 7 September 2026.

Used together?

The peptide directory lists a blend named "Tesamorelin + Ipamorelin" under blends. Its entry describes a combination of an approved GHRH analogue with an unapproved ghrelin receptor agonist, and it notes that the mixture holds no approval. The directory also lists a three-part blend, "Tesamorelin + Ipamorelin + CJC-1295 (No DAC)".

No study of tesamorelin and ipamorelin given together could be found in the ipamorelin or tesamorelin 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 ^[4]. No clinical study has tested ipamorelin with CJC-1295 either, a pairing the FDA record calls fashionable ^[4].

Frequently asked questions

Which is better, ipamorelin or tesamorelin?

The studies cannot answer that, because no trial comparing the two could be found in the sources reviewed for this page. Over 26 weeks in 412 adults with HIV and lipodystrophy, tesamorelin lowered deep belly fat by 15.2 per cent. On placebo it rose by 5.0 per cent. Ipamorelin was tested in 117 adults after bowel surgery, on a different question, and missed its main goal.

Is ipamorelin or tesamorelin 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. Tesamorelin's official product information lists injection-site reactions in 17 per cent of treated participants, against 6 per cent on placebo. For ipamorelin, the human safety data come from one analysis of 114 participants, and for many standard safety tests no results could be found.

What is the difference between ipamorelin and tesamorelin?

Both prompt the pituitary gland to release the body's own growth hormone. Tesamorelin copies the natural releasing hormone, 44 building blocks long, and uses its receptor. Ipamorelin has five building blocks and acts on the receptor for the hunger hormone ghrelin. Tesamorelin is an approved medicine in the United States, while work on ipamorelin stopped in 2014.

Can ipamorelin and tesamorelin be taken together?

No study of the two given together could be found in the sources behind this page. The peptide directory lists a blend called Tesamorelin + Ipamorelin and notes that the mixture holds no approval. Combining them changes nothing about their status in sport, where both are banned at all times.

Are ipamorelin and tesamorelin approved medicines?

Tesamorelin is, but only in the United States, where it has been prescription-only since 10 November 2010. Its single approved use is reducing excess belly fat in adults with HIV and lipodystrophy. Ipamorelin is approved nowhere, and in Australia possessing it without authority is an offence.

Are ipamorelin and tesamorelin 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 tesamorelin among the copies of the natural releasing hormone and ipamorelin among the growth hormone secretagogues. Both count as non-specified substances, the stricter category, and tesamorelin's approval as a medicine does not change that.

Do ipamorelin or tesamorelin cause weight loss?

Tesamorelin's own label states that it is not for weight loss, because its effect on weight is neutral. In its two approval trials, body weight changed by −0.4 kg and +0.5 kg, neither different from placebo. For ipamorelin, no human study on body weight could be found in the sources reviewed for this page, and in mice it raised the proportion of body fat.

How long do ipamorelin and tesamorelin stay in the blood?

Tesamorelin has a half-life of about 11 minutes in healthy adults and reaches its peak level after roughly 9 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 routes, so they are not a like-for-like comparison.

Is tesamorelin sold as a research peptide the same as the approved medicine?

No. Twelve firms hold fourteen registrations of tesamorelin with the American regulator as an unfinished raw ingredient, which is not an approval of any medicine. Two 2026 reviews place tesamorelin, like ipamorelin, in the unregulated market for so-called research compounds, where composition and purity are unverified.