Ipamorelin: evidence, FDA status and research

Sold for anti-aging, fat loss and muscle. It does raise growth hormone in people, but the one outcome trial, in 117 bowel surgery patients, did not work.

Sold for

Ipamorelin is sold as the cleanest growth hormone secretagogue, for anti-aging, fat loss and muscle, usually paired with CJC-1295.

Studies say

Ipamorelin releases growth hormone in humans without the cortisol rise seen with GHRP-2 and GHRP-6, but the only outcome trial, in bowel surgery patients, was negative, and no study has measured body composition or aging, so the grade is C.

Why grade C. For the anti-aging and body-composition use ipamorelin is sold for, no human trial exists. The human data are a 40-volunteer dose-escalation pharmacokinetic study showing a single growth hormone pulse, a 114-patient randomised phase 2 trial in post-operative ileus that found no benefit, and a comparative hormone study of related peptides. The selectivity claim comes from rats and swine. ⁴⁶²

FDA. Ipamorelin is not approved by the FDA for any use and is sold online as a research chemical; its development for post-operative ileus was abandoned after a negative phase 2 trial. In 2023 the FDA placed it in Category 2 of its compounding lists, the category for substances with significant safety risks, and it remains there for outsourcing facilities (503B) although the nominations for pharmacy compounding (503A) were withdrawn in 2024. In October 2024 the Pharmacy Compounding Advisory Committee voted 12 to 0, with one abstention, against adding it to the 503A bulks list.

Written from 11 cited sources. Last refreshed 2026-10-27. Not physician reviewed.

What this means for you

What people take it for: Anti-aging, fat loss and muscle gain.
Can a US doctor prescribe it?: No. It is not approved and is sold as a research chemical.
Properly tested in people?: Not properly: animal or lab studies, or small uncontrolled human reports. small hormone tests, and a failed trial in 117 bowel surgery patients.

Evidence checklist

Randomised controlled trial Phase 2 ileus trial, but not the sold useyes
Human study over 100 people Phase 2 ileus trial, 114 analysedyes
More than one research group Novo Nordisk studies; no independent workno
Clinical outcomes, not surrogate markers Ileus trial negative; no body-composition datano
Human safety data beyond case reports Seven-day surgery trial; long-term unknownno

Drawn from the cited studies below. A dash means the sources give no information.

What it is

Ipamorelin is a synthetic five-amino-acid peptide developed by Novo Nordisk in the 1990s as a growth hormone secretagogue. It came out of a chemistry programme that removed two residues from GHRP-1 and found a compound that released growth hormone as well as GHRP-6 did. ²

What set it apart in the original pharmacology was selectivity. In pigs, GHRP-6 and GHRP-2 raised ACTH and cortisol along with growth hormone; ipamorelin did not, and none of them affected the other pituitary hormones. That finding is the origin of its reputation as the clean option. ²

How it works

Ipamorelin binds the ghrelin receptor (GHS-R1a) on pituitary cells and triggers a pulse of growth hormone; blockade experiments showed the effect runs through the GHRP receptor and not the GHRH receptor. Because the ghrelin receptor also drives gut motility, it was tried for the slowed bowel that follows abdominal surgery. ²⁵

What human research shows

Gobburu and colleagues infused ipamorelin at five escalating doses into eight healthy men per dose level. The peptide had a half-life of about two hours and produced a single growth hormone peak at about 40 minutes followed by an exponential fall back to baseline, with no second pulse at any dose. ⁴

The one trial with a clinical endpoint randomised 117 adults undergoing bowel resection to intravenous ipamorelin or placebo for up to seven days. Among the 114 analysed, median time to tolerating a solid meal was 25.3 hours with ipamorelin against 32.6 hours with placebo, a difference that was not statistically significant, and no secondary endpoint favoured the drug. The compound was well tolerated. ⁶

No study has measured muscle mass, fat, sleep, skin or any aging-related outcome after ipamorelin in people. ⁸

Study	Model	Finding
Raun 1998, pharmacology	Rat pituitary cells, rats and swine	Ipamorelin released growth hormone as potently as GHRP-6 without raising ACTH or cortisol, unlike GHRP-2 and GHRP-6. ²
Gobburu 1999, PK/PD	Humans, n=40 healthy men, dose-escalation infusion	Two-hour half-life and a single growth hormone pulse peaking at 40 minutes at every dose. ⁴
Beck 2014, post-operative ileus	Humans, n=114, randomised double-blind placebo-controlled phase 2	Time to first tolerated meal was 25.3 versus 32.6 hours, not statistically significant; no secondary endpoint met. ⁶
Venkova 2009, rat ileus model	Rats with post-operative ileus	Ipamorelin accelerated gastric emptying and colonic transit, supporting the later human trial. ⁵

Safety

In the 114-patient surgical trial, adverse events were common in both arms (87.5% ipamorelin, 94.8% placebo) as expected after bowel surgery, with nothing attributable to the drug over seven days. The selectivity data suggest less cortisol disturbance than GHRP-2 or GHRP-6, but that is from pigs. Long-term use has not been studied in people, so effects on glucose tolerance and IGF-1-related risks are unknown. Ipamorelin is detectable in urine by anti-doping laboratories, and online products are untested for purity. ⁶²¹¹

Questions for your clinician

Is there any controlled human trial for the use I have in mind?
What happens to glucose and IGF-1 with long-term use?
Would anti-doping tests matter for me?

Questions people ask

Has ipamorelin been approved by the FDA?

No. Novo Nordisk developed it, took it to a phase 2 trial for post-operative ileus that failed, and stopped. It has no approved indication anywhere. ⁶

How did the FDA's peptide category list change for ipamorelin?

In September 2023 the FDA put ipamorelin in Category 2, meaning compounding pharmacies may not use it because of significant safety concerns. In 2024 the nominators withdrew their nominations and it was removed from Category 2, and the FDA sent it to its Pharmacy Compounding Advisory Committee, where the agency's briefing weighed against placing it on the approved bulk substances list. Removal from a category is not approval. ⁷¹⁰

How does ipamorelin stack up against GHRP-2 and GHRP-6?

All three act on the ghrelin receptor and release growth hormone to a similar degree. In the original animal pharmacology GHRP-2 and GHRP-6 also raised ACTH and cortisol while ipamorelin did not, and in humans GHRP-2 and hexarelin raise cortisol and prolactin. Ipamorelin is also the only one of the group taken into a controlled clinical trial. ²⁹⁶

Citations

Cleveland Clinic: ghrelin overview my.clevelandclinic.org
Raun 1998, European Journal of Endocrinology: ipamorelin, the first selective growth hormone secretagogue pubmed.ncbi.nlm.nih.gov
Growth Hormone and IGF Research 2001: ipamorelin study doi.org
Gobburu 1999, Pharmaceutical Research: pharmacokinetic-pharmacodynamic modeling of ipamorelin in human volunteers pubmed.ncbi.nlm.nih.gov
Venkova 2009, Journal of Pharmacology and Experimental Therapeutics: ipamorelin in a rat model of post-operative ileus doi.org
Beck 2014, International Journal of Colorectal Disease: randomised proof-of-concept study of ipamorelin for post-operative ileus pubmed.ncbi.nlm.nih.gov
FDA: certain bulk drug substances for use in compounding may present significant safety risks fda.gov
Ghigo 1997, European Journal of Endocrinology: growth hormone-releasing peptides, review pubmed.ncbi.nlm.nih.gov
Arvat 1997, Peptides: effects of GHRP-2 and hexarelin on GH, prolactin, ACTH and cortisol in man pubmed.ncbi.nlm.nih.gov
FDA: bulk drug substances nominated for use in compounding under section 503A, category list fda.gov
Thomas 2012, Journal of Chromatography A: determination of prohibited small peptides in urine for sports drug testing pubmed.ncbi.nlm.nih.gov