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PeptideLimited humanNot FDA approved

Ipamorelin

Ipamorelin

Last reviewed October 27, 2026 · 25 sources · Written for general readers · Compare with another compound →

The bottom line

Ipamorelin is a small lab made peptide that makes the pituitary gland release a burst of growth hormone. Its only published sizable human trial, for slow gut recovery after bowel surgery, found no clear benefit, and no human study has tested it for muscle, fat loss, sleep or aging. In mice it actually increased body fat and appetite. It was never approved, and FDA lists it as a significant safety risk for compounding by outsourcing facilities.

Where the evidence stands

What it is

Ipamorelin is a five piece peptide made in the lab.[1] Scientists at Novo Nordisk in Denmark described it in 1998 as the first selective growth hormone secretagogue, meaning a drug that triggers growth hormone release without much effect on other hormones.[2]

It mimics ghrelin, a natural hunger hormone, by acting on the ghrelin receptor.[3] It was later tested as an IV treatment for postoperative ileus, a slowdown of the gut after surgery.[4] A second, larger IV trial of 320 people for recovery of gut function was completed in 2014, but we could not find its results.[5]

Online it is often sold together with CJC-1295, a pairing FDA noted in its 2024 review of CJC-1295.[6] A 2020 FDA funded review of the research found only one human trial that met its criteria, the bowel surgery trial.[7]

Some black market products have contained altered versions of it. Drug testers in 2018 identified a copy with an extra glycine building block added to the front end.[8]

Name
Ipamorelin (Ipamorelin)
Other names
ipamorelin acetate
Type
Peptide
Sequence
Aib-His-2Nal-Phe-Lys-NH2
CAS number
170851-70-4
Formula
C38H49N9O5
Molecular weight
About 711.9 g/mol

What it does in the body

Ipamorelin does not occur in nature. It is a five piece lab made peptide that switches on the ghrelin receptor, which tells the pituitary gland to release growth hormone.[2][3] Ghrelin, the natural hormone it copies, is tied to hunger.[3]

This is the biology, area by area. A change measured in the body, like a higher blood level, does not always mean a person feels a benefit. The claims check below covers that.

Hormones

Measured in people

In healthy men given IV ipamorelin, eight per dose level, each dose caused a single burst of growth hormone that peaked about 40 minutes later, and the drug's half life was about 2 hours.[9] No human study has shown that it keeps IGF-1 raised over weeks.

Stress and other hormones

Seen in animals

In pigs, ipamorelin did not raise the stress hormones ACTH and cortisol beyond what GHRH does, even at doses far above those needed for growth hormone release, while GHRP-2 and GHRP-6 did raise them. It also left FSH, LH, prolactin and TSH unchanged.[2] This has not been checked in a controlled human trial.

Gut

Measured in people

In rats after belly surgery, IV ipamorelin sped stomach emptying and the first bowel movement, and repeated doses raised stool output and food intake.[3][10] In 114 adults after bowel surgery, though, it did not meaningfully speed the return of eating: about 25 versus 33 hours, a gap that could be chance.[4]

Bones

Seen in animals

In female rats, it sped bone growth in length over 15 days and raised bone mineral content over 12 weeks, mostly by making bones bigger rather than denser.[11][12] In rats on steroid drugs, it raised bone formation on the bone surface about four times compared with steroids alone.[13]

Muscle and protein

Seen in animals

In adult female rats on steroid drugs for 3 months, ipamorelin kept calf muscle strength higher than steroids alone.[13] In steroid treated rats over 7 days, it stopped the loss of body nitrogen, a sign of protein breakdown, though less well than growth hormone itself.[14]

Fat and appetite

Seen in animals

In mice, ipamorelin raised body weight about 15% within 2 weeks and increased body fat, even in mice unable to make growth hormone, and in mice with normal growth hormone it also raised food intake and leptin, a hormone made by fat.[15] In ferrets given chemotherapy, it reduced weight loss by about 24% but did not stop vomiting.[16]

Blood sugar

Lab finding

In pancreas tissue taken from normal and diabetic rats, ipamorelin increased insulin release in the lab.[17] A 2026 review lists blood sugar changes among side effects reported with growth hormone peptides as a group.[18]

How it works

Ipamorelin binds the ghrelin receptor, which signals the pituitary gland to release growth hormone.[2][3]

  • In rats and pigs, it raised growth hormone without raising the stress hormones ACTH and cortisol beyond what natural GHRH does.[2]
  • Related peptides GHRP-2 and GHRP-6 did raise ACTH and cortisol in the same tests.[2]
  • In healthy men given it by IV, it caused one burst of growth hormone that peaked about 40 minutes later, and the drug itself had a half life of about 2 hours.[9]
  • In rats after surgery, it helped the stomach empty and contract through the ghrelin receptor.[3]

The selectivity for growth hormone was shown in animals. It has not been confirmed in large human studies.

What the research shows

We keep animal and human evidence apart. A result in animals is a reason to study something in people, not proof that it works in people.

Animal and lab studies

Animal studies showed growth hormone release, bigger bones and more fat

  • In rat pituitary cells, anesthetized rats and awake pigs, ipamorelin released growth hormone with little effect on other hormones.[2]
  • In adult female rats given shots for 15 days, bone length grew up to about a quarter faster and body weight rose, while IGF-1 and bone turnover markers did not change.[11] Over 12 weeks, bone mineral content rose because bones got bigger, not denser.[12]
  • In adult female rats on steroid drugs for 3 months, adding ipamorelin kept calf muscle strength higher and raised bone formation about four times compared with steroids alone.[13]
  • In mice, it raised body weight about 15% within 2 weeks and increased body fat even in mice unable to make growth hormone, which means the fat gain did not come through growth hormone. In mice with normal growth hormone it also raised food intake.[15]
  • In rats after belly surgery, IV doses sped stomach emptying and bowel movement, and repeated doses also raised food intake and weight gain.[3][10]
  • In ferrets given the cancer drug cisplatin, it reduced weight loss by about 24% in the late phase but had no effect on vomiting.[16]

Limit: The gut benefit in rats did not carry over to a clear benefit in the human surgery trial.

Human studies

A few human studies, and the main trial found no clear benefit

  • In healthy men given IV ipamorelin at five dose levels, with eight men per level, each dose caused one burst of growth hormone that peaked about 40 minutes later. The drug had a half life of about 2 hours.[9]
  • That study measured blood levels only and did not report side effects in its summary.[9]
  • A phase 2 placebo controlled trial enrolled 117 adults having bowel surgery, 114 of whom were analyzed, and gave IV ipamorelin or placebo in the hospital for up to 7 days.[4]
  • The median time to tolerating a solid meal was 25.3 hours on ipamorelin versus 32.6 hours on placebo, a difference that was not statistically meaningful.[4]
  • Side effects of any kind occurred in 87.5% of the ipamorelin group and 94.8% of the placebo group, a reminder that problems are common after surgery. The drug was described as well tolerated.[4]
  • A second, larger phase 2 trial of IV ipamorelin for recovery of gut function enrolled 320 people and was completed in 2014, but no results are posted on its registry page and we found no publication.[5]
  • In a drug testing study, one volunteer took ipamorelin as a nasal spray. It was broken down heavily, and both the drug and its pieces showed up in urine.[19]
  • Doctors interviewed for a 2020 FDA funded report described using ipamorelin, sometimes with CJC-1295, but these are reported practices, not trial results.[7]
  • We found no published controlled trials of ipamorelin for muscle, fat loss, sleep, healing or aging, and none of shots under the skin as it is sold online. A 2026 review likewise found no efficacy data for growth hormone related uses.[18]

Limit: The only published sizable human trial used IV doses in hospital patients and showed no proven benefit.

Claims check

The most common claims about this compound, and what studies actually found. Verdicts rate the evidence, not whether you should use it.

Raises growth hormone

Mixed results

In healthy men, IV ipamorelin caused a short growth hormone burst that peaked about 40 minutes after each dose.[9] But this was one small study, and no human study has shown lasting rises in IGF-1 or any benefit that follows from it.

Raises growth hormone without raising cortisol or hunger

Only in animals

In rats and pigs, ipamorelin raised growth hormone, and in pigs it did not raise the stress hormones ACTH and cortisol beyond what GHRH does, unlike GHRP-2 and GHRP-6.[2] Hunger is a different story: in mice it raised food intake and leptin, and repeated doses raised food intake in rats after surgery.[15][10] Neither point has been tested in a controlled human trial.

Builds muscle

Only in animals

In adult female rats on steroid drugs for 3 months, ipamorelin preserved calf muscle strength, and in steroid treated rats it improved nitrogen balance, a marker of protein buildup.[13][14] No human study has measured muscle size or strength with ipamorelin.

Burns fat

Only in animals

No human study has tested ipamorelin for fat loss. Animal studies point the other way: in mice it increased body fat, and in rats it increased body weight.[15][12]

Strengthens bones

Only in animals

In female rats, ipamorelin sped up bone growth over 15 days and raised bone mineral content over 12 weeks, mostly by making bones bigger rather than denser.[11][12] It also countered the drop in bone formation caused by steroid drugs in rats.[13] No human bone study exists.

Speeds gut recovery after surgery

No benefit in trials so far

In a placebo controlled trial of 114 analyzed adults after bowel surgery, IV ipamorelin did not meaningfully shorten the time to tolerating solid food, a median of 25.3 hours versus 32.6 hours on placebo.[4] A larger 320 person trial of gut function recovery was completed in 2014, but no results are posted.[5]

Improves sleep and recovery

Not tested

We found no study of ipamorelin for sleep or exercise recovery in people or animals. The human studies measured hormone levels and gut recovery only.[9][4]

Known risks and side effects

  • FDA flagged serious events. FDA cites a published study reporting serious adverse events, including death, after IV ipamorelin was used to improve gut movement, and says it lacks safety data for other injection routes.[20]
  • Immune reactions and altered products. FDA warns ipamorelin may trigger immune reactions, partly because it can contain clumped or impure peptide and unusual building blocks that are hard to test.[20] Black market products have also contained altered copies of the molecule.[8]
  • Sterility recalls and unregulated vials. FDA recall records list 18 Class II recalls from 2018 to 2022 of compounded ipamorelin products, all because sterility could not be assured.[21] In August 2026 FDA warned an online seller that its ipamorelin blend, labeled for research use only, was an unapproved new drug meant for people.[22]
  • Appetite, fat and hormone effects. In mice it raised appetite and body fat.[15] A 2026 review lists raised prolactin and cortisol, blood sugar changes, fluid retention, muscle and joint aches, and injection site reactions among side effects reported with growth hormone peptides.[18]
  • No proven benefit, banned in sport. Its one published sizable human trial did not show a meaningful effect, so any side effect comes with no proven upside.[4] WADA lists ipamorelin as a prohibited growth hormone secretagogue at all times.[23]

Regulatory status

Today: Ipamorelin is not FDA approved. FDA keeps ipamorelin acetate in Category 2, meaning significant safety risks, for outsourcing facilities (503B).[20] FDA also lists it among withdrawn nominations, and its May 2026 list for regular compounding pharmacies (503A) places it in no category, even though HHS Secretary Robert F. Kennedy Jr. announced in February 2026 that about 14 peptides, reportedly including ipamorelin, would move back to Category 1.[20][24][25] Kennedy Jr. said in February 2026 that it would move back to Category 1.[20][24][25]

  1. Novo Nordisk scientists published the first description of ipamorelin.[2]
  2. A study in healthy men described how IV ipamorelin moves through the body and triggers growth hormone.[9]
  3. A 320 person phase 2 trial of IV ipamorelin for gut function recovery was completed, with no results posted.[5]
  4. Results of the first phase 2 bowel surgery trial were published online, showing no significant benefit.[4]
  5. The first of 18 sterility recalls of compounded ipamorelin products recorded through 2022 began.[21]
  6. An FDA funded report found only one published human trial of ipamorelin.[7]
  7. FDA placed ipamorelin acetate in Category 2 under the 503B interim policy.[20]
  8. HHS Secretary Robert F. Kennedy Jr. said about 14 peptides, with ipamorelin named among them in reports, would move back to Category 1.[25]
  9. FDA's updated page also lists ipamorelin acetate among withdrawn nominations, while keeping its 503B Category 2 listing.[20]
  10. FDA warned an online seller that its ipamorelin blend, labeled for research use only, was an unapproved new drug.[22]

Sources

  1. U.S. FDA and NCATS Global Substance Registration System (GSRS). Ipamorelin, UNII Y9M3S784Z6. FDA GSRS
  2. Raun K, Hansen BS, Johansen NL, Thogersen H, Madsen K, Ankersen M, Andersen PH. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-561. PMID 9849822
  3. Greenwood-Van Meerveld B, Tyler K, Mohammadi E, Pietra C. Efficacy of ipamorelin, a ghrelin mimetic, on gastric dysmotility in a rodent model of postoperative ileus. J Exp Pharmacol. 2012;4:149-155. DOI 10.2147/JEP.S35396
  4. Beck DE, Sweeney WB, McCarter MD. Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Int J Colorectal Dis. 2014;29(12):1527-1534. PMID 25331030
  5. Helsinn Therapeutics (U.S.), Inc. Safety and Efficacy of Ipamorelin Compared to Placebo for the Recovery of Gastrointestinal Function. ClinicalTrials.gov NCT01280344. NCT01280344
  6. Tu M, Albuquerque E, Benedict A, San Antonio M, Kasim S, Mattingly A, Rupp T. FDA Evaluation of CJC-1295 Related Bulk Drug Substances. Briefing document for the Pharmacy Compounding Advisory Committee meeting of December 4, 2024. U.S. Food and Drug Administration; November 15, 2024. FDA briefing document
  7. University of Maryland Center of Excellence in Regulatory Science and Innovation (M-CERSI). Summary Report: Ipamorelin Acetate. Prepared for the U.S. Food and Drug Administration under grant 5U01FD005946. December 2020. M-CERSI report
  8. Krug O, Thomas A, Malerød-Fjeld H, Dehnes Y, Laussmann T, Feldmann I, et al. Analysis of new growth promoting black market products. Growth Horm IGF Res. 2018;41:1-6. PMID 29864719
  9. Gobburu JV, Agersø H, Jusko WJ, Ynddal L. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res. 1999;16(9):1412-1416. PMID 10496658
  10. Venkova K, Mann W, Nelson R, Greenwood-Van Meerveld B. Efficacy of ipamorelin, a novel ghrelin mimetic, in a rodent model of postoperative ileus. J Pharmacol Exp Ther. 2009;329(3):1110-1116. PMID 19289567
  11. Johansen PB, Nowak J, Skjaerbaek C, Flyvbjerg A, Andreassen TT, Wilken M, Orskov H. Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats. Growth Horm IGF Res. 1999;9(2):106-113. PMID 10373343
  12. Svensson J, Lall S, Dickson SL, Bengtsson BA, Rømer J, Ahnfelt-Rønne I, Ohlsson C, Jansson JO. The GH secretagogues ipamorelin and GH-releasing peptide-6 increase bone mineral content in adult female rats. J Endocrinol. 2000;165(3):569-577. PMID 10828840
  13. Andersen NB, Malmlöf K, Johansen PB, Andreassen TT, Ørtoft G, Oxlund H. The growth hormone secretagogue ipamorelin counteracts glucocorticoid-induced decrease in bone formation of adult rats. Growth Horm IGF Res. 2001;11(5):266-272. PMID 11735244
  14. Aagaard NK, Grøfte T, Greisen J, Malmlöf K, Johansen PB, Grønbaek H, Ørskov H, Tygstrup N, Vilstrup H. Growth hormone and growth hormone secretagogue effects on nitrogen balance and urea synthesis in steroid treated rats. Growth Horm IGF Res. 2009;19(5):426-431. PMID 19231263
  15. Lall S, Tung LY, Ohlsson C, Jansson JO, Dickson SL. Growth hormone (GH)-independent stimulation of adiposity by GH secretagogues. Biochem Biophys Res Commun. 2001;280(1):132-138. PMID 11162489
  16. Lu Z, Ngan MP, Liu JYH, Yang L, Tu L, Chan SW, Giuliano C, Lovati E, Pietra C, Rudd JA. The growth hormone secretagogue receptor 1a agonists, anamorelin and ipamorelin, inhibit cisplatin-induced weight loss in ferrets: Anamorelin also exhibits anti-emetic effects via a central mechanism. Physiol Behav. 2024;284:114644. PMID 39043357
  17. Adeghate E, Ponery AS. Mechanism of ipamorelin-evoked insulin release from the pancreas of normal and diabetic rats. Neuro Endocrinol Lett. 2004;25(6):403-406. PMID 15665799
  18. Dominikowski A, Rękoś Z, Olejarz M, Szczepanek-Parulska E, Domin R, Ruchała M. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. Front Endocrinol (Lausanne). 2026;17:1822475. PMID 42395176
  19. Semenistaya E, Zvereva I, Thomas A, Thevis M, Krotov G, Rodchenkov G. Determination of growth hormone releasing peptides metabolites in human urine after nasal administration of GHRP-1, GHRP-2, GHRP-6, Hexarelin, and Ipamorelin. Drug Test Anal. 2015;7(10):919-925. PMID 25869809
  20. U.S. Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. Content current as of April 22, 2026. FDA
  21. U.S. Food and Drug Administration. openFDA Drug Enforcement Reports: recalls of products listing ipamorelin (18 Class II recalls initiated 2018 to 2022). Accessed October 29, 2026. openFDA recalls
  22. U.S. Food and Drug Administration. Warning letter 733652 to an online peptide seller. August 24, 2026. FDA warning letter
  23. World Anti-Doping Agency. The 2026 Prohibited List, section S2.2.4 Growth hormone releasing factors. In force January 1, 2026. WADA 2026
  24. U.S. Food and Drug Administration. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the FD&C Act (categories list). Updated May 14, 2026. FDA 503A categories
  25. Atta H. 5 Things to Know About the FDA's Peptide Reversal. American Journal of Managed Care (AJMC). August 21, 2026. AJMC news
Medical disclaimer

This page is educational information only. It is not medical advice and does not replace care from a licensed medical provider. Do not use this page to decide whether to take any substance. Talk to a licensed medical provider first.

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