Hexarelin and ipamorelin are both growth-hormone-releasing peptides that work through the ghrelin receptor, and on vendor pages they are listed side by side with the same 100 to 300 mcg figures. The published record treats them differently. Hexarelin left a run of 1990s human endocrine studies, with dose-response curves and a 16-week repeated-dosing trial; ipamorelin left a selectivity paper in animals and two intravenous programmes in people. This page sets the two records side by side as the papers state them (abstracts re-read 2026-10-12), converts every dose into micrograms, molecules and syringe units, and marks what no study has compared. It reports; it suggests no dose.
Each compound's full record is on its own page: hexarelin dosage and ipamorelin dosage. The neighbouring comparison in the same class is GHRP-2 vs GHRP-6.
The two molecules
| Hexarelin | Ipamorelin | |
|---|---|---|
| Residues | 6 (His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2) | 5 |
| Formula, molecular weight | C47H58N12O6, 887.0 | C38H49N9O5, 711.9 |
| Receptor | Ghrelin receptor (GHS-R1a) | Ghrelin receptor (GHS-R1a) |
| Developed | Italy, early 1990s | Novo Nordisk, 1998 paper |
| Approved product | None | None |
| PubMed records naming both | 9 on 2026-10-12, all doping-control chemistry and one 2026 review | — |
Ipamorelin was found inside a series of compounds built by removing the central Ala-Trp from GHRP-1, which is why it is one residue shorter. Hexarelin is GHRP-6 with one tryptophan methylated. The nine papers that name both are drug-testing studies — urine metabolites after nasal doses, receptor-binding assays — and the 2026 performance-peptide review; none gives both to the same people.
What each record contains
| Hexarelin | Ipamorelin | |
|---|---|---|
| Human dose-response | Yes: intravenous 0.5–2 mcg/kg (12 men) and 0–1 mcg/kg (healthy men) | Intravenous infusion, 4.21–140.45 nmol/kg over 15 min, 8 men per level |
| Routes tested in people | Intravenous, subcutaneous, intranasal, oral | Intravenous only |
| Longest human study | 16 weeks, 1.5 mcg/kg SC twice daily | 7 days, 0.03 mg/kg IV twice daily after bowel surgery |
| Half-life | Response peak ~30 min, gone within ~4 h | Terminal half-life 2 h; GH peak at 0.67 h |
| Cortisol and prolactin | Raised in humans (prolactin plateau +180%; cortisol ~+40% from 0.5 mcg/kg) | Not raised in swine, even at >200× the GH ED50 |
The last row is the reason the two are compared at all, and its two halves are not the same kind of evidence. Massoud's hexarelin figures come from healthy men; Raun's ipamorelin figures come from conscious pigs. Ipamorelin's human pharmacokinetic study measured growth hormone, not cortisol or prolactin, in its abstract. So "ipamorelin does not raise cortisol" is an animal finding that no human study has repeated against hexarelin.
Doses in micrograms and molecules
Hexarelin's studies used micrograms per kilogram; ipamorelin's used nanomoles per kilogram. Put on one scale at 70 kg (this site's arithmetic from the published figures and the PubChem weights):
| Study dose | mcg/kg | mcg at 70 kg | nmol at 70 kg |
|---|---|---|---|
| Hexarelin, half-maximal GH (Massoud) | 0.48 | 34 | 38 |
| Hexarelin, plateau (Massoud) | 1 | 70 | 79 |
| Hexarelin, 16-week SC dose (Rahim) | 1.5 | 105 | 118 |
| Ipamorelin, lowest infusion (Gobburu) | ≈3.0 | 210 | 295 |
| Ipamorelin, highest infusion (Gobburu) | ≈100 | 7,000 | 9,832 |
| Ipamorelin, ileus trial (0.03 mg/kg) | 30 | 2,100 | 2,950 |
Two things stand out. Hexarelin's growth-hormone response in people flattened at about 1 mcg/kg, a dose lower than ipamorelin's lowest human infusion. And the ipamorelin doses actually given to people were 2 to 7 mg at 70 kg, by vein — ten to seventy times the subcutaneous figures on vendor pages. Neither observation makes one peptide more potent than the other; the studies measured different things in different designs.
Per microgram, ipamorelin carries more molecules because it is lighter: 100 mcg is about 140 nmol of ipamorelin and 113 nmol of hexarelin, a ratio of 1.25.
Repeated dosing
Only hexarelin has a published answer to what happens over weeks. In Rahim's adults, 1.5 mcg/kg under the skin twice daily lowered the growth-hormone response to a test dose by 31% at week 1, 36% at week 4 and 45% at week 16; four weeks after stopping it was back to baseline, and IGF-1, body fat and lean mass had not changed significantly. Ipamorelin's longest human exposure is seven days of intravenous dosing after surgery, with time to first tolerated meal 25.3 against 32.6 hours on placebo, not significant. Whether ipamorelin's response fades the same way has not been studied in people.
Regulatory and sport status
| Hexarelin | Ipamorelin | |
|---|---|---|
| FDA safety-risk list (content current 2026-04-22) | Not listed | Listed: "serious adverse events including death when ipamorelin was administered intravenously for improving gastric motility" |
| DailyMed / openFDA labels | None | None |
| WADA 2026 | S2.2.4, "examorelin (hexarelin)" among the GH-releasing peptides | S2.2.4, ipamorelin among the "growth hormone secretagogues (GHS) and their mimetics" |
The FDA entry for ipamorelin also notes that it contains unnatural amino acids, which complicates characterising a compounded product. Hexarelin's absence from that list reflects that it was not nominated for compounding, not a finding about its safety.
The same amounts in syringe units
At equal concentrations the units are identical, whichever peptide is in the vial. The flat vendor figures and the 70 kg hexarelin trial dose, each in 2 mL of water:
| Amount | 2 mg vial (1,000 mcg/mL) | 5 mg vial (2,500 mcg/mL) | 10 mg vial (5,000 mcg/mL) |
|---|---|---|---|
| 100 mcg | 10 units | 4 units | 2 units |
| 105 mcg (1.5 mcg/kg × 70 kg) | 10.5 units | 4.2 units | 2.1 units |
| 200 mcg | 20 units | 8 units | 4 units |
| 300 mcg | 30 units | 12 units | 6 units |
Hexarelin is sold in 2, 5 and 10 mg vials and ipamorelin in 5 and 10 mg. On the 10 mg vials every figure is a two- to six-unit draw; how those marks read on each barrel size is on insulin syringe units. Any other combination is worked by the hexarelin calculator and the ipamorelin calculator.
What is not established
No study has given hexarelin and ipamorelin to the same people, so there is no human comparison of potency, selectivity or tolerance. Ipamorelin's cortisol-sparing profile is an animal result. Neither compound has a trial of subcutaneous use for body composition, recovery or performance, and neither has an approved product. The vendor figures shared by both are conventions, not study doses. Product and dose decisions belong with a clinician. Medibact's hexarelin guide and ipamorelin guide cover each compound.
Sources and dates
Opened 2026-10-12: PubMed abstracts PMIDs 8954038 (Massoud 1996), 9849822 (Raun 1998), 10496658 (Gobburu 1999), 26811125 (Ferro 2017) and the PubMed search naming both compounds (9 records); PubChem CIDs 6918297 and 9831659; FDA, "Certain bulk drug substances for use in compounding that may present significant safety risks" (content current as of 2026-04-22); the 2026 WADA Prohibited List as published in Tractatenblad 2026 no. 25, section S2.2.4. From the compound pages on this site, opened 2026-09-18 and 2026-10-11: Imbimbo 1994 (PMID 7957536), Ghigo 1994 (PMID 8126144), Rahim 1998 (PMID 9589671) and Beck 2014. Per-kilogram, molar and unit arithmetic by this site. Corrections go to the contact page.