Does it build muscle?

No published study has looked. The two human studies measured bowel recovery after surgery and growth hormone in the blood. Neither weighed anyone, scanned anyone or measured strength. Rats given it under the skin for 15 days grew faster and gained weight, and that is the whole of the evidence behind what it is sold for.

Why did the drug company stop developing it?

It did not work well enough. The 2014 trial in 114 people after bowel surgery missed its main target and showed no difference from a dummy drip on the other measures either. A larger 320-person trial finished in May 2014 and its results have never been posted or published anywhere. Development stopped there and it was never approved as a medicine.

The studies used a drip into a vein. It is sold as an injection under the skin. Does that matter?

It matters and nobody knows by how much. In 2024 the US regulator looked for measurements of ipamorelin given under the skin. It found none at all: no blood levels, no growth hormone response, no safety data. In rats, roughly a fifth of a dose sprayed into the nose reached the bloodstream. The regulator also noted that injecting a peptide under the skin is the route most likely to provoke an immune reaction.

Can a pharmacy legally make it up for me in the United States?

It is not on the list of bulk ingredients that pharmacies are allowed to compound with. In October 2024 the US regulator put that question to its advisory committee, having already proposed keeping ipamorelin off the list. The committee voted 0 in favour of adding it, 12 against, with 1 abstention, and the members who voted against said the safety and effectiveness data were not there.

Is it true that it raises growth hormone without raising stress hormones?

That is what the original 1998 study found, in rat cells, anaesthetised rats and conscious pigs. Ipamorelin released growth hormone without raising the stress hormones ACTH and cortisol, unlike the related compounds GHRP-2 and GHRP-6, which raised both. Nobody has repeated that measurement in a person.

Would it show up in a drugs test?

It is on the World Anti-Doping Agency's prohibited list, in the section covering substances that make the body release its own growth hormone. The regulator's 2024 review notes that ipamorelin has been found in vials confiscated from athletes in Germany, Belgium and Australia, and in confiscated vials in the United States.

Unregulated compound

This has no approved use in people anywhere in the EU, and is sold as a research chemical. Nobody checks what is in the vial, how pure it is, or how much it contains. Peptide Reader describes what the evidence says — it is not a suggestion to use it.

Gray market

Ipamorelin

Also known as NNC 26-0161

Still being tested in people

7 of 51 peptides sit at this level

Category: Gray market
Doping status: Banned in sport
Sources: 12

Ipamorelin is a small synthetic peptide that makes the pituitary gland — a gland the size of a pea under the brain — release a pulse of growth hormone. That pulse is the only thing anyone has measured properly in people. A 1999 study enrolled 48 healthy men and gave five different single amounts as a drip into a vein. In the men who received it, the pulse was over within six hours. It was later tested in hospital patients whose bowels had stopped working after surgery, where it failed to beat a dummy drip, and development stopped. It has never been approved as a medicine anywhere. No published study has looked at muscle, body fat, sleep or ageing. No study in people has ever used the injection under the skin that it is sold for.

IpamorelinWhat it is

What it is
Sold and legal
In your body
What changed
What can go wrong
Amounts studied
What people say
Unknowns
Questions
Sources

What it is

A synthetic five-amino-acid peptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) that prompts the body to release growth hormone. The chain contains building blocks outside the standard set — aminoisobutyric acid, and mirror-image forms of two others — so it cannot be written in one-letter code; we mark it unknown rather than print an incorrect string. Developed by Novo Nordisk in the 1990s and later tested by Helsinn for bowel paralysis after surgery.

How it is sold, and whether it is legal

Sold as: Injection under the skin.
Legal status in the EU: Not approved as a medicine in the EU or anywhere else. Named on the doping list among growth hormone secretagogues, alongside lenomorelin (ghrelin), anamorelin, macimorelin and tabimorelin (Antidoping Sweden, 2023 doping list, section S2, point 2.4).

What it does in your body

6 parts of the body · 3 from one small study, 2 only seen in animals, 1 claimed but never tested

It switches on the ghrelin receptor in the pituitary gland, which releases growth hormone. In the original characterisation (Raun et al., Eur J Endocrinol 1998, in rat cells, anaesthetised rats and conscious pigs) ipamorelin released growth hormone without raising stress hormones any more than GHRH did — unlike the related compounds GHRP-2 and GHRP-6.

The pituitary gland, and growth hormone in the blood: Ipamorelin switches on the receptor that the hunger hormone ghrelin normally uses, and the pituitary gland answers with one sharp pulse of growth hormone. Growth hormone in the blood peaks about 40 minutes after the drip starts. It has fallen back to very little by six hours. Nothing about it is sustained: it is a single pulse per dose.; One dose-finding study. 48 healthy men were enrolled; at each of five amounts, six were given ipamorelin as a 15-minute drip into a vein and two were given a dummy drip. Blood was sampled over the following hours. The same pulse had been seen before that in rat cells, anaesthetised rats and conscious pigs.; One small study; Source [01]Source [06]Source [07]
Stomach and gut: The receptor ipamorelin acts on also sits in the gut. That is why it was taken into hospital trials, to restart bowels that go quiet after abdominal surgery. In the one published trial, patients given ipamorelin managed a solid meal about seven hours sooner than patients on a dummy drip. The difference was small enough that it could have been chance. Time to a first bowel movement and time to being ready to leave hospital were no different.; One trial. 117 adults were enrolled and 114 were treated and analysed, all of whom had just had part of the bowel removed. Treatment ran from the first day after surgery until day seven or discharge.; One small study; Source [07]Source [08]
Blood sugar: Growth hormone works against insulin, so blood sugar tends to drift up when it rises. In the one trial that measured it, more people on ipamorelin had high blood sugar recorded when they left hospital than people on the dummy drip. The regulator that reviewed the compound treats this as the expected direction of travel. Every approved medicine that raises growth hormone carries a warning about blood sugar and diabetes on its label.; High blood sugar at discharge in 14.3% on ipamorelin against 8.6% on a dummy drip, among the 114 adults treated for up to seven days after bowel surgery. Nobody has measured blood sugar over months.; One small study; Source [07]Source [08]
Bones and body weight — in rats: Rats were given ipamorelin under the skin three times a day for 15 days. Their long bones grew faster and they put on weight, more so at higher amounts. The blood markers that usually go up when growth hormone is working did not move. Those markers are IGF-1, the hormone growth hormone normally triggers, and the substances in blood that show bone being built and broken down.; Adult female rats, three injections a day for 15 days, three amounts against an injection of the carrier liquid alone. No equivalent study has ever been done in a person.; Only seen in animals; Source [09]
Appetite: Ipamorelin acts on the receptor for ghrelin, the hormone that makes people feel hungry, so an appetite effect is the obvious thing to look for. Ferrets were given a chemotherapy drug that makes them sick. Ipamorelin injected into the belly cut the weight they lost on the third day, 48 to 72 hours in, by about 24%. It did not reduce the vomiting at all. In rats it increased weight gain. No published study has measured appetite in a person given ipamorelin.; Ferrets dosed every 24 hours and watched for 72 hours; rats over 15 days. Nothing in people.; Only seen in animals; Source [09]Source [10]
Sleep: Better and deeper sleep is the effect ipamorelin is most often sold and discussed for. No published study in people has measured sleep on ipamorelin — not with a sleep laboratory, not with a questionnaire, not at all. The only sleep-related number that exists points the other way. In the bowel surgery trial, trouble sleeping was recorded in more of the patients given ipamorelin than of those given the dummy drip.; The US medicines regulator searched the published literature, the trials register and two adverse event databases in 2024. It found one clinical trial in patients, the bowel surgery one, and the 1999 dose-finding study in healthy men. Neither measured sleep. Trouble sleeping was recorded in 10.7% on ipamorelin against 5.2% on the dummy drip in the bowel surgery trial.; Claimed, never tested; Source [07]Source [08]

What changed when it was measured

4 findings · 3 from one small study, 1 only seen in animals

Ipamorelin has been through two completed phase 2 studies in humans, both in bowel paralysis after surgery and both sponsored by Helsinn Therapeutics: NCT00672074 (117 participants, 2008–2009) and NCT01280344 (320 participants, 2011–2014). Neither registry entry has posted results, and no results have been published separately. Development was not taken further and the substance was never approved. No published study has looked at muscle mass, body composition or ageing — which are the uses it is sold for on the gray market. The 1998 characterisation contained no human data.

Fast and short. After a 15-minute drip into a vein, growth hormone in the blood peaks at about 40 minutes and is back to very little by six hours. The compound itself has a half-life of about two hours, meaning half of it is cleared from the blood in that time. In the bowel surgery trial the outcome was measured within a day or two of the first dose. The longest anyone has been given ipamorelin in a published study is seven days. Nobody has published what happens after a month, a year or repeated courses.

Time until someone could eat a solid meal again after bowel surgery: 25.3 hours from the first dose, against 32.6 hours on a dummy drip. The difference was not statistically significant, meaning it is within what chance can produce.; 114 adults who had had part of the small or large bowel removed, treated from day one after surgery until day seven or discharge; One small study; Source [08]
Time to a first bowel movement, and time until ready to leave hospital: No difference between ipamorelin and the dummy drip on any of these. The trial's own combined measure of upper and lower gut recovery did not separate the groups either.; The same 114 adults after bowel surgery; One small study; Source [07]Source [08]
Growth hormone in the blood: One pulse per dose, peaking about 40 minutes after a 15-minute drip started and down to very little by six hours. The men given a dummy drip, and those given the lowest amount, released so little growth hormone that both were left out of the analysis.; 48 healthy men enrolled; at each of five amounts, six were given ipamorelin and two a dummy drip, as a single dose; One small study; Source [06]Source [07]
Bone growth rate in rats: 42 micrometres a day on the carrier liquid alone, against 44, 50 and 52 micrometres a day on the three increasing amounts of ipamorelin.; Adult female rats, injected under the skin three times a day for 15 days; Only seen in animals; Source [09]

What can go wrong

8 effects, 3 serious

No safety results have been published from either phase 2 study, even though they finished in 2009 and 2014. Both also involved a different patient group and a short course of treatment. Switching on the ghrelin receptor increases appetite and can affect blood sugar control. The effects of repeated use over years have not been studied.

Death after surgerySerious: Both had had bowel removed for colon cancer and both developed a leak where the bowel had been joined back together. One died of high blood potassium, blood poisoning and a perforated ulcer, with clots in the aorta, the body's main artery. The other died of kidney failure and blood poisoning, with pneumonia. The trial authors and the US regulator both say it is not known whether ipamorelin had anything to do with them. The regulator still counted them as a reason for concern.; Two of the 56 people given ipamorelin in the one published trial; Source [07]Source [08]
Serious complications after surgery — infection, a leak at the join in the bowel, readmission to hospitalSerious: Infections were the most common, at almost the same rate in both groups: six people on ipamorelin and six on the dummy drip. Most of these happened after treatment had finished. The trial was too small to tell whether the small excess on ipamorelin means anything.; 10 of 56 people on ipamorelin (17.9%) against 9 of 58 on the dummy drip (15.5%); Source [07]
An immune reaction to the injection itselfSerious: Small peptides can clump together in the vial, and the body can start making antibodies against them. That can range from nothing noticeable to a severe reaction. The US regulator raised this specifically for ipamorelin in 2024. Injecting under the skin is the route it is sold for. The regulator noted that this route carries more of this risk than a drip into a vein. It said it could not rule the risk out, because the information needed to judge it does not exist.; Not measured. No study of ipamorelin has ever tested for it.; Source [07]
High blood sugar: Expected from anything that raises growth hormone. Every approved medicine that raises growth hormone carries a label warning about poor blood sugar control and diabetes. Nobody has measured what happens over months.; 14.3% on ipamorelin against 8.6% on the dummy drip, measured at hospital discharge; Source [07]
Low potassium in the blood: Potassium is one of the salts the heart and muscles need to work. This was the clearest imbalance between the two groups in the trial. It was picked up on hospital blood tests in people who had just had surgery, so it is not known whether it would happen outside that setting.; 12.5% on ipamorelin against 3.4% on the dummy drip; Source [07]
Trouble sleeping: Recorded by the hospital staff during the treatment days. It is the only sleep figure that exists for ipamorelin, and it runs opposite to what the compound is usually sold for.; 10.7% on ipamorelin against 5.2% on the dummy drip; Source [07]
Feeling sick, being sick and a swollen belly: Everyone in the trial had just had bowel surgery, which causes all three by itself, so these figures say little about the compound. Three people on ipamorelin stopped treatment early, for feeling sick, high blood pressure or low blood pressure. Three on the dummy drip stopped for low blood sodium, being sick, feeling sick or a swollen belly.; The most common problems in the trial, in both groups, and slightly less common on ipamorelin than on the dummy drip; Source [07]Source [08]
Reports sent to the US regulator by the public: One was a 32-year-old man who used a nasal spray containing ipamorelin once a day for 17 days and had watering eyes and headache. The website that sold it took payment by Venmo to avoid the authorities, and it no longer works. The other was a 46-year-old man who injected an ipamorelin and sermorelin mixture for two months and developed left elbow pain. The pain eased but did not go away after he stopped. A second database covering food and supplements had no reports at all. Two reports is not a safety record — almost nobody reports anything bought outside a pharmacy.; Two reports in total up to 30 September 2023, both non-serious, both about products made up by a compounding pharmacy; Source [07]

Who it is known to be dangerous for

Nobody has established this. Ipamorelin has never been approved, so it has never been given the warnings section that an approved medicine gets. What is on record: the one human trial deliberately excluded people with Crohn's disease, irritable bowel syndrome and complicated bowel operations, so nothing is known about them. Anything that raises growth hormone raises the questions listed on the labels of approved growth hormone products. Those labels warn about tumours, poor blood sugar control and diabetes, raised pressure inside the skull, fluid retention, and hip and spine problems in children. Ipamorelin works by asking the pituitary gland to release its own growth hormone. The regulator states plainly that it will do nothing in someone whose pituitary cannot produce any. In mice, both switching the ghrelin receptor on and blocking it interfered with fertilisation, implantation of the embryo and its development. No pregnancy data of any kind exist for ipamorelin. It is on the World Anti-Doping Agency's prohibited list, in the section covering substances that make the body release its own growth hormone.

The amounts the studies used

4 amounts

These are the amounts the studies below gave their participants, and they are here as facts about those studies. They are not a recommendation, not a starting point and not a range to pick from. What a person should take, if anything, is a question for a doctor who knows them.

Gobburu et al. 1999, the only study of ipamorelin in healthy people, measuring growth hormone release: Five single amounts were tested, one per group of eight men: 4.21, 14.02, 42.13, 84.27 and 140.45 nanomoles per kilogram of body weight. Each was given as a 15-minute drip into a vein. Six men in each group received ipamorelin and two received a dummy drip.; A single dose; Source [06]Source [07]
Beck et al. 2014 (trial NCT00672074), bowels restarting after bowel surgery: 0.03 mg per kilogram of body weight, infused into a vein, twice a day; From the first day after surgery until day seven or leaving hospital, whichever came first; Source [03]Source [08]
NCT01280344, the larger follow-up trial in people recovering from bowel surgery. It finished in 2014 and no results have ever been posted or published: Four groups, all infused into a vein. Three received ipamorelin: 0.03 mg per kilogram twice a day, 0.06 mg per kilogram twice a day, or 0.06 mg per kilogram three times a day. The fourth received a dummy drip three times a day.; Up to 10 days in hospital, with a 14-day follow-up visit afterwards; Source [02]
Johansen et al. 1999, rats. This is the only published study that gave ipamorelin under the skin repeatedly — the way it is sold — and it was not in people: 18, 90 or 450 micrograms a day per rat, split over three injections under the skin, against the carrier liquid alone; 15 days; Source [09]

What people report

What follows is what people say online. It is not evidence, it is not graded, and it is not checked by anyone. People who had a bad time and people who are selling something both post more than people for whom nothing happened. It is here because you would go and read it anyway, and knowing who is talking is better than not.

Almost nobody takes it on its own

Post after post is about ipamorelin mixed with CJC-1295 or tesamorelin, injected under the skin, often at night. When one poster asked in July 2026 whether ipamorelin alone was enough for sleep, one reply was 'No point to that' and another was 'Never tried ipa alone'.

Read in r/Peptides, the thread 'Ipamorelin alone vs. Ipamorelin + CJC (no DAC) for sleep?' (26 July 2026, 9 comments). Other July 2026 threads in the same subreddit are titled 'Cjc 1295 no dac Ipamorelin', 'Tesa + Ipa Lab results' and 'CJC-1295 AND IPAMORELIN SIDE EFFECT'.