Ipamorelin vs GHRP-6: both are injected peptides that trigger a short burst of growth hormone through the ghrelin receptor, and in animals they release similar amounts.[1] The difference is what else they do. GHRP-6, the 1984 prototype, drives hunger and roughly doubled cortisol and prolactin at the highest dose tested in healthy men.[2][4][7] Ipamorelin did not raise ACTH or cortisol in pigs, even at doses over 200 times its effective dose.[1] Neither is FDA-approved, and FDA lists both among compounding substances that may present significant safety risks.[13]
See the ipamorelin and GHRP-6 profiles, or the growth hormone peptides hub.
Ipamorelin vs GHRP-6 at a glance
| Ipamorelin | GHRP-6 | |
|---|---|---|
| Size | 5 amino acids[1] | 6 amino acids[2] |
| First described | 1998[1] | 1984[2] |
| Growth hormone release (animals) | Similar to GHRP-6[1] | The benchmark[1] |
| Cortisol / ACTH | Not raised in pigs[1] | Raised in pigs;[1] about doubled at highest dose in men[4] |
| Hunger | Raised food intake in mice[9] | Strong appetite effect in animals[7] |
| Half-life in people (IV) | About 2 hours[6] | About 2.5 hours[5] |
| Best human use | None proven; failed surgery trial[10] | Diagnostic growth hormone test[11] |
| FDA compounding status | Category 2 safety risk (503B); advisers voted 0 to 12 (503A)[13][15] | Category 2 safety risk (503B); category 3 (503A)[13][14] |
How they work
Ghrelin is a hormone, mostly from the stomach, that both triggers hunger and tells the pituitary to release growth hormone. GHRP-6 was discovered before ghrelin itself: Cyril Bowers and colleagues showed in 1984 that it released growth hormone in several animal species without changing other pituitary hormones such as LH, FSH, TSH or prolactin.[2]
Ipamorelin was developed by a Danish drug program as a cleaner version. In rat pituitary cells, rats and pigs, it released growth hormone with potency and strength similar to GHRP-6. In pigs, GHRP-6 and GHRP-2 raised ACTH and cortisol, while ipamorelin did not.[1] None of the peptides changed prolactin in that pig study.[1]
Both work best alongside the brain’s own growth hormone-releasing hormone (GHRH). In healthy men, low doses of GHRP-6 plus GHRH released more growth hormone than the two effects added together.[4] This is why ghrelin-type peptides are often paired with GHRH analogs; see CJC-1295 + ipamorelin.
Human evidence
GHRP-6
- First human study: in 17 healthy men, an IV infusion raised growth hormone in a dose-related way without changing LH, FSH, TSH or ACTH.[3]
- Diagnosis: GHRH plus GHRP-6 separated adults with growth hormone deficiency from healthy adults in a large hospital study.[11]
- Stroke: in a 2026 phase III trial from Cuba, GHRP-6 combined with epidermal growth factor did not meet its main goal of reducing disability at 6 months.[12]
Ipamorelin
- Healthy men: single IV infusions caused one growth hormone pulse peaking at about 40 minutes.[6]
- After bowel surgery: a phase 2 trial in 114 patients did not significantly shorten time to tolerating solid food.[10]
Appetite: the biggest practical difference
GHRP-6 is known for hunger. Injected into rats’ brains, it triggered eating separately from its effect on growth hormone.[7] Ghrelin, which uses the same receptor, made all nine volunteers in a London study eat more at a buffet, by 28% on average.[8] No controlled human feeding study of GHRP-6 has been published.
Ipamorelin is often marketed as appetite-neutral, but that claim has not been tested in people. In mice, two weeks of ipamorelin or GHRP-6 increased body fat, and ipamorelin raised food intake, through effects not caused by growth hormone.[9]
Side effects and safety
- GHRP-6: in healthy men, prolactin and cortisol roughly doubled, but only at the highest IV dose.[4] FDA cites possible effects on cortisol and blood sugar.[13]
- Ipamorelin: in the surgery trial, adverse events were common in both groups and similar to placebo.[10]
- Both: FDA warns that compounded versions may trigger immune reactions for some routes of use because peptides can clump and carry impurities.[13] A 2026 review lists appetite changes, raised prolactin or cortisol, blood sugar disturbances, fluid retention and injection-site reactions across this class.[17]
Doses used in studies
Neither peptide has an approved dose, so research doses are the only reference. A clinician decides whether any use is appropriate.
| Setting | Ipamorelin | GHRP-6 |
|---|---|---|
| Healthy men, single IV dose | Escalating 15-minute infusions[6] | 0.1 to 1 mcg per kg[4] |
| Diagnostic test | Not used | 1 mcg per kg IV with GHRH[11] |
| Patients, repeated doses | 0.03 mg per kg IV twice daily after bowel surgery[10] | IV twice daily for 7 days with EGF in stroke[12] |
Most of these studies gave the peptides by vein, in hospital or research settings, for short periods. Neither has a published efficacy trial using injection under the skin, the way they are sold online. Dosing schedules circulating online come from forums and sellers rather than research.[17]
Legal status
- Not approved: neither has FDA approval for any use.[13]
- Ipamorelin: in October 2024, FDA’s compounding advisers voted 0 to 12, with one abstention, against adding it to the 503A list. It has been in category 2 for outsourcing facilities since September 2023.[15][13]
- GHRP-6: category 2 for outsourcing facilities since September 2023, and category 3 (nominated without adequate support) on the May 2026 503A list.[13][14]
- Sport: WADA bans both at all times.[16]
See the FDA peptide compounding crackdown for context. This is general information, not legal advice.
Questions to discuss with a clinician
- Are you trying to gain weight or appetite? GHRP-6’s hunger effect is a side effect for most people and the main point for some; neither use is approved.[7]
- Do you have diabetes, high cortisol or a pituitary condition? Both peptides affect hormones beyond growth hormone in at least some studies.[4][13]
- Is there an approved alternative? For diagnosed growth hormone deficiency, see peptides vs HGH; for older GHRH-based options, see sermorelin vs ipamorelin.
The verdict
GHRP-6 is the better-studied prototype, with decades of hormone studies and a real diagnostic use, but it brings hunger and, at higher doses, more cortisol and prolactin.[4][11] Ipamorelin is the more selective peptide in animals, yet its one efficacy trial failed.[1][10] Neither has proven benefits for body composition. For more side-by-side reviews, see hexarelin vs ipamorelin and GHRP-2 vs GHRP-6 vs hexarelin.
