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PeptideLimited humanNot FDA approved

Ipamorelin

Ipamorelin

Last reviewed October 27, 2026 · 11 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 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. 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 a treatment for postoperative ileus, a slowdown of the gut after surgery.[4]

Online it is often sold together with CJC-1295, a pairing FDA noted in its 2024 review of CJC-1295.[5]

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

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.[6]
  • 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 and bigger bones

  • 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 a little faster, from 42 to as much as 52 micrometers a day, and body weight rose. IGF-1 and bone turnover markers did not change.[7]
  • In young adult female rats given a steady infusion under the skin for 12 weeks, bone mineral content and body weight rose. The bones got bigger, not denser.[8]
  • In a rat model of gut slowdown after surgery, an IV dose sped up stomach emptying compared with no drug.[3]

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

Human studies

Two human studies, and the main trial found no clear benefit

  • In a study of healthy men given IV ipamorelin, in groups of eight, each dose caused one burst of growth hormone that peaked about 40 minutes later. The drug had a half life of about 2 hours.[6]
  • That study measured blood levels only and did not report side effects in its summary.[6]
  • A phase 2 placebo controlled trial enrolled 117 adults having bowel surgery and gave IV ipamorelin or placebo in the hospital for up to 7 days.[4]
  • Time to eating a solid meal was about 25 hours on ipamorelin versus 33 hours on placebo, a gap that was not statistically meaningful.[4]
  • Side effect rates were similar between the ipamorelin and placebo groups, and the drug was described as well tolerated.[4]
  • 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.

Limit: The only 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.[6] 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 without raising the stress hormones ACTH and cortisol beyond what GHRH does, unlike GHRP-2 and GHRP-6.[2] This selectivity has not been tested in a controlled human trial, and we found no human study of its effect on hunger.

Builds muscle

Not tested

No published human or animal study we found measured muscle growth or strength with ipamorelin. Rat studies showed weight gain and bigger bones, not proven muscle gain.[7][8]

Burns fat

Not tested

We found no study in people that tested ipamorelin for fat loss. In rats, it increased body weight rather than lowering it.[7][8]

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.[7][8] No human bone study exists.

Speeds gut recovery after surgery

No benefit in trials so far

In a placebo controlled trial of 117 adults after bowel surgery, IV ipamorelin did not meaningfully shorten the time to eating solid food, about 25 hours versus 33 hours on placebo.[4]

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.[6][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.[9]
  • Immune reactions and impurities. 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.[9]
  • No proven benefit. Its one sizable human trial did not show a meaningful effect, so any side effect comes with no proven upside.[4]
  • Unregulated products. Ipamorelin sold online is not an approved drug, so purity, strength and sterility are unknown.[9]
  • Banned in sport. WADA lists ipamorelin as a prohibited growth hormone secretagogue at all times.[10]

Regulatory status

Today: Ipamorelin is not FDA approved. FDA keeps ipamorelin acetate in Category 2, meaning significant safety risks, for outsourcing facilities (503B).[9] FDA also lists it among withdrawn nominations, and its May 2026 list for regular compounding pharmacies (503A) places it in no category.[9][11]

  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.[6]
  3. Results of the phase 2 bowel surgery trial were published, showing no significant benefit.[4]
  4. FDA placed ipamorelin acetate in Category 2 under the 503B interim policy.[9]
  5. FDA's updated page also lists ipamorelin acetate among withdrawn nominations, while keeping its 503B Category 2 listing.[9]

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. 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
  6. 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
  7. 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
  8. 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
  9. 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
  10. World Anti-Doping Agency. The 2026 Prohibited List, section S2.2.4 Growth hormone releasing factors. In force January 1, 2026. WADA 2026
  11. 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
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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