Comparison
GHRP-6 vs Ipamorelin
Both are gHRPs & ghrelin mimetics, so the meaningful differences are in kinetics, evidence and regulatory status.
On published evidence alone, GHRP-6 is the better documented of the two (clinical trials). That is a statement about the state of the literature, not a recommendation.
| GHRP-6 | Ipamorelin | |
|---|---|---|
| Class | GHRPs & ghrelin mimetics | GHRPs & ghrelin mimetics |
| Evidence | Clinical trials | Preliminary human |
| Human trials | ~10 | ~5 |
| Half-life | ~15-30 minutes | ~2 hours |
| Reported range | 100-300 mcg | 200-300 mcg |
| Frequency | 2-3x daily | 1-3x daily, on an empty stomach |
| Routes | Subcutaneous, Intramuscular | Subcutaneous |
| FDA approved | No | No |
| Research use only | Yes | Yes |
| Banned in sport | Yes | Yes |
| Studied for | Appetite stimulation, Growth hormone elevation, Recovery research | Growth hormone elevation, Recovery, Sleep quality, Body composition |
| Reported side effects | Pronounced hunger, Elevated cortisol and prolactin, Water retention, Head rush | Head rush on injection, Transient hunger, Water retention, Lethargy |
GHRP-6
GHRP-6 is a hexapeptide agonist at the growth hormone secretagogue receptor and was the first of the class to be characterised. Its defining clinical feature is a strong, rapid increase in hunger through central ghrelin-receptor activation, considerably greater than ipamorelin or GHRP-2. That appetite effect is the reason it is selected in bulking contexts and avoided in fat-loss contexts.
Ipamorelin
Ipamorelin is a pentapeptide agonist at the growth hormone secretagogue receptor, the same receptor targeted by endogenous ghrelin. Unlike the earlier GHRPs it produces a GH pulse without meaningful elevation of adrenocorticotropic hormone, cortisol or prolactin, which is the basis of its reputation as the cleanest compound in the class. It is short-acting and is typically dosed alongside a GHRH analog to exploit the synergy between the two receptor pathways.
GHRP-6 vs Ipamorelin: common questions
What is the difference between GHRP-6 and Ipamorelin?
Both are gHRPs & ghrelin mimetics. GHRP-6: The original growth-hormone-releasing hexapeptide, now used as much for its pronounced appetite stimulation as for GH release. Ipamorelin: The most receptor-selective of the growth-hormone-releasing peptides, notable for leaving cortisol and prolactin essentially unchanged.
Which has stronger evidence, GHRP-6 or Ipamorelin?
GHRP-6 has the stronger evidence base (clinical trials, about 10 human studies) compared with Ipamorelin (preliminary human).
Are GHRP-6 and Ipamorelin FDA approved?
Neither is FDA approved for any indication.
References
Regulatory and primary sources
- PubChem compound record (CID 4345065) ↗ · structure, identifiers, synonyms
- WADA Prohibited List ↗ · current year
- FDA: Unapproved drugs and "research use only" products ↗ · regulatory status of non-approved products
- CAS Registry Number 87616-84-0 ↗ · chemical identity
- PubChem compound record (CID 9831659) ↗ · structure, identifiers, synonyms
- CAS Registry Number 170851-70-4 ↗ · chemical identity
Published literature
- Growth hormone-releasing peptides.Eur J Endocrinol 1997.PubMed 9186261 · doi:10.1530/eje.0.1360445
- Growth hormone in obesity.Int J Obes Relat Metab Disord 1999.PubMed 10193871 · doi:10.1038/sj.ijo.0800807
- Diagnosis of adult GH deficiency.Pituitary 2008.PubMed 18404387 · doi:10.1007/s11102-008-0110-x
- The Safety and Efficacy of Growth Hormone Secretagogues.Sex Med Rev 2018.PubMed 28400207 · doi:10.1016/j.sxmr.2017.02.004
- Growth hormone releasing hexapeptide-6 (GHRP-6) test in the diagnosis of GH-deficiency.J Pediatr Endocrinol Metab 1996.PubMed 8887178
- Physiology of ghrelin and related peptides.Domest Anim Endocrinol 2005.PubMed 15927771 · doi:10.1016/j.domaniend.2005.02.033
- Growth hormone secretagogue receptor family members and ligands.Endocrine 2001.PubMed 11322507 · doi:10.1385/ENDO:14:1:009
- Growth hormone-releasing peptides and their analogs.Front Neuroendocrinol 1998.PubMed 9465289 · doi:10.1006/frne.1997.0158
- Injectable Peptide Therapy: A Primer for Orthopaedic and Sports Medicine Physicians.Am J Sports Med 2026.PubMed 41476424 · doi:10.1177/03635465251357593
- Therapeutic Peptides in Orthopaedics: Applications, Challenges, and Future Directions.J Am Acad Orthop Surg Glob Res Rev 2026.PubMed 41490200 · doi:10.5435/JAAOSGlobal-D-25-00236
- Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance.Sports Med 2026.PubMed 41966639 · doi:10.1007/s40279-026-02437-0
- Therapeutic Peptides in Aesthetic, Metabolic and Endocrine Conditions: Effects, Safety, Clinical Applications, and Future Perspectives.Int J Mol Sci 2026.PubMed 42123471 · doi:10.3390/ijms27093890
- A new era of doping? Use of peptide and peptide-analog drugs in recreational and professional sport and bodybuilding: a critical review.J Sports Med Phys Fitness 2026.PubMed 41880199 · doi:10.23736/S0022-4707.26.17773-1
- Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers.Pharm Res 1999.PubMed 10496658 · doi:10.1023/a:1018955126402
- 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.PubMed 25331030 · doi:10.1007/s00384-014-2030-8
- Injectable Peptides in Sports Medicine: A Structured Narrative Review of Evidence, Safety, and Antidoping Implications.JBJS Rev 2026.PubMed 42160466 · doi:10.2106/JBJS.RVW.26.00027
Literature retrieved from PubMed on October 16, 2026, favouring human studies and reviews. Numbered markers in the text show which paper supports which statement; uncited entries are background reading.