People asking which is better usually mean which works better. The record can't answer that, because no trial has put the two side by side. What it can answer is which one a US pharmacy may make. Sermorelin was an FDA-approved drug until 2009 and is compounded today [7]. Ipamorelin was never approved, and FDA's compounding advisers voted it down without a single yes [2].
They raise growth hormone through two different receptors
Your pituitary gland has two main accelerators for growth hormone. One is GHRH, the hormone your hypothalamus releases to say "make more." The other is the ghrelin receptor, the same receptor the hunger hormone ghrelin uses.
Sermorelin works on the first. It is a lab-made copy of the first 29 amino acids of GHRH, called GHRH(1-29) in the studies that led to its approval [12]. Ipamorelin works on the second. The 2014 phase 2 trial calls it a ghrelin mimetic [11], and the paper that introduced it calls it a selective growth-hormone secretagogue [9].
Neither contains growth hormone. Both depend on a pituitary that can still respond. That shared limit is why the useful first question for anyone with low growth hormone is whether a deficiency has been tested for, not which peptide to pick.
Side by side: the approval history decides more than the chemistry
| Sermorelin | Ipamorelin | |
|---|---|---|
| What it is | GHRH(1-29), a fragment of growth-hormone-releasing hormone | A five-amino-acid ghrelin mimetic [9] |
| FDA status | Approved as Geref until 2009; withdrawn at the maker's request, not for safety [7] | Never approved |
| Route to a US patient | Compounded drug, by prescription; 503B Category 1, under evaluation [6] | None: not on the 503A bulks list; 503B Category 2 since September 29, 2023 [3] |
| Advisory vote | None held | 0 yes, 12 no, 1 abstention on each form, October 29, 2024 [2] |
| Largest human study | 110 children with GH deficiency, open-label [12] | 117 adults after bowel surgery, randomized [11] |
| Strongest result | Height velocity in children rose from 1.6 to 3.1 inches (4.1 to 8.0 cm) a year at 6 months | None: the phase 2 trial missed its goal |
| Safety signals FDA raised | No current label, so no current official safety section | 2 deaths (cause unclear), more high blood sugar, immune-reaction risk [1] |
| Sport | Prohibited at all times, WADA S2.2.4 (GHRH analogs) [15] | Prohibited at all times, WADA S2.2.4 (secretagogues) [15] |
Neither has an FDA-approved adult use. Sermorelin's adult prescriptions are off-label.
Ipamorelin's human record is one dosing study and one failed trial
The first human study gave ipamorelin by IV to healthy men to see how the body handles it. Every dose level produced a single pulse of growth hormone, and the drug's half-life was about 2 hours [10]. It measured hormone levels only, not any benefit.
The second was the trial that mattered. Ipamorelin was developed to speed up gut recovery after bowel surgery, and 117 adults were randomized to it or to placebo. Median time to a first tolerated solid meal was 25.3 hours on ipamorelin and 32.6 hours on placebo. That gap was not statistically significant (p = 0.15), and no efficacy measure differed significantly [11].
Its "selective" reputation comes from animals. In rat pituitary cells and pigs, it released growth hormone about as strongly as the older peptide GHRP-6 without raising the stress hormones ACTH and cortisol [9]. No human trial has shown that this selectivity changes any outcome you would notice.
Sermorelin's record: clear in children, thin in adults
In children with growth-hormone deficiency, the use Geref was approved for, sermorelin worked. In an open-label study of 110 untreated children, height velocity rose from 1.6 inches (4.1 cm) a year to 3.1 inches (8.0 cm) at 6 months and 2.8 inches (7.2 cm) at 12 months [12]. There was no control group.
Adults are where the evidence runs out. In 11 healthy men aged 64 to 76, 6 weeks of sermorelin raised night-time growth hormone. It didn't change IGF-1, weight, or muscle and fat on DEXA scans, though 2 of 6 strength measures improved [13]. A second study often quoted used a close analog, not sermorelin itself, in 19 older adults [14].
| Study | Peptide | Who and how many | What it found |
|---|---|---|---|
| Gobburu 1999 [10] | Ipamorelin | Healthy men, 8 per dose level, IV | One growth-hormone pulse per dose; half-life about 2 hours |
| Beck 2014 [11] | Ipamorelin | 117 adults after bowel surgery, randomized | 25.3 vs 32.6 hours to first meal, not significant |
| Raun 1998 [9] | Ipamorelin | Rat cells, rats and pigs | Growth-hormone release without ACTH or cortisol rises (animal data) |
| Thorner 1996 [12] | Sermorelin | 110 children with GH deficiency, open-label | Height velocity 1.6 to 3.1 inches (4.1 to 8.0 cm) a year at 6 months |
| Vittone 1997 [13] | Sermorelin | 11 men aged 64 to 76, no control | Night-time GH up; IGF-1, muscle and fat unchanged |
| Khorram 1997 [14] | Close analog | 19 older adults | GH and IGF-1 rose; a different molecule |
Safety: FDA's ipamorelin review found signals; sermorelin has no current label
FDA's 2024 briefing went back through the surgery trial. Two patients on ipamorelin died after leaks at the surgical join, and FDA wrote that it is unclear whether the deaths were related to the drug [1]. Serious adverse events ran 17.9% on ipamorelin and 15.5% on placebo.
Two other numbers pointed the same way: high blood sugar at discharge, 14.3% against 8.6%, and insomnia, 10.7% against 5.2% [1]. FDA also notes that compounded ipamorelin may trigger immune reactions because of aggregation or impurities [3]. Those patients were recovering from surgery, so the figures don't describe healthy adults, but they are the only controlled safety data there are. Water retention questions are covered in does ipamorelin cause water retention.
Sermorelin's studies reported it as well tolerated, with no adverse changes in routine blood tests in the children's study [12]. Those studies were small and are decades old, and with no current FDA label there is no up-to-date official list of side effects. What is and isn't known is on is sermorelin safe.
Status: sermorelin has a pharmacy route, ipamorelin has none
Ipamorelin's path closed in steps. FDA placed ipamorelin acetate in Category 2 on both compounding lists on September 29, 2023 [4]. The nominations were withdrawn in September 2024, and FDA took it off the 503A Category 2 list on September 27, 2024, but still put the question to its advisers [5].
On October 29, 2024, the committee voted on whether to add ipamorelin: 0 yes, 12 no, 1 abstention for the free base, and the same for the acetate [2]. There is no USP monograph and no approved drug containing it, so the bulks list was its only possible route [1]. FDA keeps the acetate in Category 2 of its 503B list as of this update [3].
Sermorelin's history runs the other way. FDA approved Geref in 1990 and 1997, withdrew the approvals at the maker's request in 2009 [8], and found in 2013 that they were not withdrawn for safety or effectiveness reasons [7]. Today it is sold as a compounded drug and sits in Category 1 of the 503B list [6]. The full approval story is on is sermorelin FDA approved.
Sermorelin and ipamorelin together: no study has tested it
Some clinics pair a GHRH peptide with a ghrelin mimetic on the theory that pressing both accelerators works better. No published trial has tested sermorelin with ipamorelin. The more common pairing, CJC-1295 with ipamorelin, has no trial either, and both halves of that pair were voted down by FDA's advisers. That pairing has its own page: CJC-1295 and ipamorelin.
Related matchups: tesamorelin vs sermorelin and tesamorelin vs ipamorelin. What sermorelin costs from telehealth providers is on the sermorelin page. How this site weighs evidence and status is in how we check.