Ipamorelin is sold widely as a growth hormone peptide. The human evidence behind it is small. It comes down to one dosing study in healthy men and one mid-stage trial after bowel surgery. Neither tested muscle, fat loss, sleep or aging, which are the uses it is marketed for.
It is research-only on this site. That means the page describes what studies used, not what anyone should take.
What ipamorelin is
Ipamorelin is a pentapeptide, a chain of five amino acids, first described by Novo Nordisk researchers in 1998 [1]. It binds the ghrelin receptor, the same target as the older growth-hormone-releasing peptides such as GHRP-6.
That 1998 paper is rat, swine and cell work, not human data. In swine, ipamorelin released growth hormone without raising ACTH or cortisol, even at doses over 200 times the effective dose. The authors called it the first selective growth hormone secretagogue. How it compares with sermorelin, which works on a different receptor, is covered separately.
The one human dosing study
In 1999, researchers gave ipamorelin by 15-minute infusion to healthy men at five dose levels, eight men per level [2]. The doses ran from 4.21 to 140.45 nmol/kg.
Its half-life was about 2 hours. Each dose produced a single pulse of growth hormone that peaked at 0.67 hours, then fell to negligible levels. The response varied more between people than the drug levels did. The study measured blood levels only; it did not measure any health outcome.
The bowel-surgery trial
The one published efficacy trial asked a narrow question. Could ipamorelin speed the return of gut function after bowel surgery [3]? It enrolled 117 adults, of whom 114 made up the analysis groups.
Patients got 0.03 mg/kg by vein, or placebo, twice a day for up to 7 days. Median time to a tolerated solid meal was 25.3 hours on ipamorelin and 32.6 hours on placebo. That difference was not statistically significant (p = 0.15). The authors found no significant difference on any key or secondary outcome.
Adverse events were common in both groups: 87.5% on ipamorelin and 94.8% on placebo. The authors called the drug well tolerated. They also note the trial was small and enrolled patients with a broad range of conditions.
A second phase 2 trial from the same sponsor tested higher doses in 320 patients. Its registry record lists it as completed in 2014, with no results posted [4].
What has never been tested in people
None of these studies measured ipamorelin’s effect on muscle, body fat, sleep, injury recovery or aging in people. The bone and growth findings often quoted online come from rats. Blends that pair it with another peptide add a second unknown; the evidence for the most common pairing is in CJC 1295 and ipamorelin.
The legal side, including what “research use only” labels mean, is in are peptides legal. For approved options with human trials, start at the recovery goal page.