Hexarelin is one of the growth-hormone-releasing peptides of the early 1990s, a six-residue relative of GHRP-6 developed in Italy and tested in a run of small endocrine studies between 1994 and 2002. It was never approved. What it left behind is unusually detailed for a research peptide: dose-response curves, bioavailability by four routes, and a 16-week study showing what happens to the response when it is given repeatedly. This page sets out those figures as the papers state them (abstracts read 2026-10-11), converts the per-kilogram doses into micrograms and syringe units, and places the figures circulating online beside them. It reports; it suggests no dose.
The arithmetic for any vial size is on the hexarelin calculator; the class it belongs to is compared on GHRP-2 vs GHRP-6 and the ipamorelin dosage page, the selective secretagogue of the same family.
What the trials gave, by route
| Study (year, PMID) | Subjects | Route | Dose |
|---|---|---|---|
| Imbimbo (1994, 7957536) | 12 healthy men | Intravenous, single | 0.5, 1, 2 mcg/kg |
| Ghigo (1994, 8126144) | 12 healthy young adults | Intravenous / subcutaneous / intranasal / oral | 1–2 mcg/kg / 1.5–3 mcg/kg / 20 mcg/kg / 20 and 40 mg |
| Laron (1994, 7955465) | 10 short children, 2 GH-deficient adults | Intravenous vs intranasal | 1 mcg/kg vs 20 mcg/kg |
| Laron (1995, 8548949) | 8 prepubertal short children | Intranasal, three times daily, up to 8 months | 60 mcg/kg |
| Massoud (1996, 8954038) | Healthy men | Intravenous, single | 0 to 1 mcg/kg (plus 0.125 with GHRH) |
| Rahim (1998, 9589671) | Adults | Subcutaneous, twice daily, 16 weeks | 1.5 mcg/kg |
Every injected dose sits between 0.125 and 3 mcg/kg. The intranasal and oral doses are ten to several thousand times larger because so little of them is absorbed.
Where the response stops rising
Two dose-response studies agree on the shape. In Imbimbo's 12 men, peak growth hormone rose from 26.9 ng/mL at 0.5 mcg/kg to 52.3 at 1 mcg/kg and only to 55.0 at 2 mcg/kg; the calculated half-maximal dose was 0.50 to 0.64 mcg/kg, and the authors describe 2 mcg/kg as very close to the maximum. Massoud's study put the plateau at 1 mcg/kg, with a half-maximal dose of 0.48 mcg/kg. In both, the growth-hormone peak came about 30 minutes after the injection and faded within about four hours.
At 70 kg the half-maximal dose is about 34 to 45 mcg intravenously and the plateau begins near 70 mcg. Under the skin, where Ghigo measured 77% of the intravenous effect, the equivalent amounts are roughly 30% higher. The 100 to 200 mcg figures recorded online in the 2026 review are therefore at or above the amount at which these studies saw the growth-hormone response flatten in a 70 kg adult — a comparison of numbers, not a statement that any amount is suitable for anyone.
Absorption by route
Ghigo's four-route study measured how much of each dose behaved as if injected into a vein:
| Route | Dose tested | Bioavailability | Dose × bioavailability (70 kg) |
|---|---|---|---|
| Subcutaneous | 1.5 and 3 mcg/kg | 77% | 81 and 162 mcg effective of 105 and 210 |
| Intranasal | 20 mcg/kg | 4.8% | ≈67 mcg effective of 1,400 |
| Oral | 20 mg | 0.3% | ≈60 mcg effective of 20,000 |
The last column is this site's arithmetic. It shows why the paper found the intranasal 20 mcg/kg response close to the intravenous 1 mcg/kg response: after absorption, the two deliver roughly the same amount. It also shows how wasteful the non-injected routes are — a 20 mg oral dose is ten 2 mg vials.
Hormones beyond growth hormone
Hexarelin is not selective. Massoud found prolactin rising up to 180% from baseline (plateau at 1 mcg/kg) and cortisol rising about 40% from 0.5 mcg/kg; Laron's children showed a small fall in TSH within the normal range. A very low dose, 0.125 mcg/kg, given together with GHRH produced a large growth-hormone release with a moderate prolactin rise and no cortisol rise. The 2026 review lists reduced slow-wave sleep and stimulation of the ACTH, cortisol and prolactin axes among the reported effects. This is the main point of difference from ipamorelin, which was developed to avoid the cortisol and prolactin response; the two records are set against each other dose by dose in the hexarelin and ipamorelin comparison.
Repeated dosing: the 16-week study
Rahim and colleagues gave adults 1.5 mcg/kg under the skin twice daily for 16 weeks and measured the growth-hormone response to a single test injection along the way:
| Week | GH response (area, µg/L·h) | Change from week 0 |
|---|---|---|
| 0 | 19.1 | — |
| 1 | 13.1 | −31% |
| 4 | 12.3 | −36% |
| 16 | 10.5 | −45% |
| 20 (4 weeks after stopping) | 19.4 | +2% |
The percentages are this site's arithmetic on the published means. Serum IGF-1 and IGF binding protein-3 did not change significantly over the 20 weeks, and neither did body fat, lean body mass or bone density; of the bone markers, only one collagen propeptide rose. The authors concluded that this schedule's effect on the GH–IGF-1 axis "seems to be minimal". The online pattern of 8 to 12 weeks on and 4 weeks off happens to match the study's four-week recovery; no study tested that cycle.
The doses in micrograms and units
Trial doses at three body weights, and their units from a 2 mg vial in 2 mL of bacteriostatic water (1,000 mcg/mL, 10 mcg per unit):
| Dose | 60 kg | 70 kg | 90 kg | Units at 70 kg (2 mg in 2 mL) |
|---|---|---|---|---|
| 0.5 mcg/kg | 30 mcg | 35 mcg | 45 mcg | 3.5 |
| 1 mcg/kg | 60 mcg | 70 mcg | 90 mcg | 7 |
| 1.5 mcg/kg | 90 mcg | 105 mcg | 135 mcg | 10.5 |
| 2 mcg/kg | 120 mcg | 140 mcg | 180 mcg | 14 |
| 3 mcg/kg | 180 mcg | 210 mcg | 270 mcg | 21 |
The flat online figures on the three vial sizes the calculator carries, each in 2 mL:
| 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 |
| 150 mcg | 15 units | 6 units | 3 units |
| 200 mcg | 20 units | 8 units | 4 units |
On the 10 mg vial every figure is a two- to four-unit draw, where one unit is 25–50% of the amount; adding more water is the only thing that spreads it over more marks. A 2 mg vial holds twenty 100 mcg amounts or ten 200 mcg amounts at any water volume. How unit marks read on each barrel size is on insulin syringe units.
What is not established
No trial measured body composition, performance or recovery as an outcome; the 2026 review grades the evidence as phase I/II endocrine studies only. The long-term study was 16 weeks in adults; nothing longer exists. Hexarelin has no label, no current registration and no approved product, and its anti-doping status is explicit. Product and dose decisions belong with a clinician. The compound is covered in Medibact's hexarelin guide.
Sources and dates
Opened 2026-10-11: PubMed abstracts PMIDs 7957536, 8126144, 7955465, 8548949, 8954038 and 9589671; the 2026 review by Dominikowski et al. (PMC13322892), tables 1 and 2; PubChem CID 6918297; openFDA drug-label and ClinicalTrials.gov searches for hexarelin and examorelin (no records); the 2026 WADA Prohibited List as published in Tractatenblad 2026 no. 25, section S2.2.4. PubMed held 314 records for hexarelin, 192 tagged as human, on the same day. Per-kilogram conversions, units, effective-dose and percentage arithmetic by this site. Corrections go to the contact page.