Hexarelin vs ipamorelin: both are lab-made peptides that make the pituitary release growth hormone through the ghrelin receptor. Hexarelin is the stronger releaser in human studies, but it also raises cortisol and prolactin and its effect fades by about 45% with daily use.[1][3][4] Ipamorelin was designed to be selective: in pigs it released growth hormone without raising stress hormones.[2] Neither is FDA-approved, and neither has a published trial showing benefits for muscle, fat loss or aging.[13][17]
See the hexarelin and ipamorelin profiles, or the growth hormone peptides hub.
Hexarelin vs ipamorelin at a glance
| Hexarelin | Ipamorelin | |
|---|---|---|
| Size | 6 amino acids; built from GHRP-6[1] | 5 amino acids[2] |
| Growth hormone release | Strong; about twice GHRH at 1 mcg/kg IV[1] | Similar to GHRP-6 in animals[2] |
| Cortisol and prolactin | Raised at higher doses[3] | Not raised in pigs[2] |
| Half-life / timing | Growth hormone back to baseline within about 4 hours[6] | Half-life about 2 hours[5] |
| Fades with daily use | Yes, about 45% over 16 weeks[4] | Not studied in people |
| Extra target | CD36 receptor in the heart[8] | None known |
| Longest human study | 16 weeks in older adults[4] | Up to 7 days IV after surgery[10] |
| FDA status | Not approved; not on compounding lists[15] | Not approved; advisers voted 0 to 12 against compounding[13] |
How each one works
Both belong to the growth hormone-releasing peptides (GHRPs), which act on the ghrelin receptor and add to the effect of the brain’s own growth hormone-releasing hormone.[18]
Hexarelin was made in the early 1990s by swapping one amino acid in GHRP-6. In 12 young volunteers, an IV dose released about twice as much growth hormone as GHRH, and it also worked under the skin (about 77% of the IV response) but barely by mouth.[1] Growth hormone peaked about 30 minutes after an IV dose, and the response was near its maximum at 2 mcg/kg.[6] Hexarelin also binds CD36, a receptor in heart tissue, which may explain heart effects seen in animals.[8]
Ipamorelin came from a Danish drug program in the 1990s. In rats and pigs it matched GHRP-6 for growth hormone release. Unlike GHRP-6 and GHRP-2, it did not raise ACTH or cortisol, even at doses more than 200 times its effective dose.[2] In healthy men, single IV infusions caused one growth hormone pulse that peaked at about 40 minutes and then faded, with a half-life of about 2 hours.[5]
Evidence quality
Both have short-term human data on hormone levels. Neither has outcome trials for the uses they are marketed for.
Hexarelin in people
- Long-term use: 12 healthy older adults injected 1.5 mcg/kg twice daily for 16 weeks. The growth hormone response fell by about 45% and returned to baseline four weeks after stopping. IGF-1, body fat, lean mass and bone density did not change significantly.[4][7]
- Heart surgery: in a small study of men with coronary disease, a single 2 mcg/kg IV dose during bypass surgery raised heart pumping within 10 minutes; GHRH and growth hormone did not.[9]
Ipamorelin in people
- Healthy men: a dose-ranging study measured blood levels and growth hormone only.[5]
- After bowel surgery: in a phase 2 trial of 114 patients, IV ipamorelin twice daily did not significantly speed recovery of gut function versus placebo.[10]
- Fat: in mice, ipamorelin increased body fat and food intake through effects not caused by growth hormone.[12]
Side effects and safety
Hexarelin
- Stress hormones: in healthy men, higher IV doses raised prolactin by up to 180% and cortisol by about 40%.[3]
- Sleep: four night-time doses reduced deep sleep in young volunteers and raised ACTH, cortisol and prolactin overnight.[11]
- No safety review: FDA has not published a safety evaluation of hexarelin.[14][15]
Ipamorelin
- Hospital data: in the surgery trial, adverse events were common in both groups (87.5% on ipamorelin, 94.8% on placebo).[10]
- Immune risk: FDA lists ipamorelin among compounding substances that may present significant safety risks, citing possible immune reactions.[14]
Both: a 2026 review of growth hormone peptides listed reported problems such as raised prolactin or cortisol, appetite changes, blood sugar disturbances, fluid retention and injection-site reactions.[17] Neither has long-term safety data in healthy adults.
Doses used in studies
No dose of either peptide is approved, so research doses are the only reference. A clinician decides whether any use is appropriate.
| Setting | Hexarelin | Ipamorelin |
|---|---|---|
| Single IV dose, healthy adults | 0.5 to 2 mcg per kg[6] | Five escalating 15-minute infusions in healthy men[5] |
| Repeated use | 1.5 mcg per kg under the skin twice daily for 16 weeks[4] | 0.03 mg per kg IV twice daily for up to 7 days after surgery[10] |
Two points stand out. Hexarelin’s response was close to its maximum at about 2 mcg per kg, while prolactin and cortisol rose at higher doses.[6][3] And no published efficacy trial has tested ipamorelin injected under the skin, which is how it is sold. Online dosing schedules come from forums and sellers, not from these studies.[17]
Legal status and access
- Ipamorelin: in October 2024, FDA’s compounding advisory committee voted 0 to 12, with one abstention, against adding it to the list traditional pharmacies may compound.[13]
- Hexarelin: it does not appear on FDA’s 503A nomination list or its safety-risk list, so it falls outside FDA’s interim compounding policies.[15][14]
- Sport: WADA bans both at all times; hexarelin appears as examorelin.[16]
Because neither is approved or eligible for compounding, there is no regulated product or price to compare. See peptides on the WADA prohibited list. This is general information, not legal advice.
Questions to discuss with a clinician
- Do you actually have low growth hormone? Diagnosed deficiency has approved treatments; see peptides vs HGH.
- Do you have heart disease, sleep problems or high cortisol? Hexarelin’s effects on the heart, sleep and stress hormones have only been studied in single or short doses.[9][11]
- Is your goal fat loss? Ipamorelin increased fat in mice, and neither peptide changed body composition in people.[12][4]
The verdict
Hexarelin is the more potent releaser in human studies, with intriguing single-dose heart data, but it raises stress hormones and loses some of its effect with daily use.[3][4] Ipamorelin looked more selective in animals but failed its one efficacy trial.[2][10] What is known: both raise growth hormone briefly. What is not known: whether either improves health, muscle or fat in people. For related comparisons, see ipamorelin vs GHRP-6, GHRP-2 vs GHRP-6 vs hexarelin and MK-677 vs CJC-1295 ipamorelin.
