GHRP-6 (growth hormone-releasing peptide-6) is a lab-made peptide, six amino acids long, that makes the pituitary gland release growth hormone. Cyril Bowers and colleagues described it in 1984, and it became the first such peptide shown to work in living animals.[1][2] It acts on the ghrelin receptor, the same switch the hunger hormone ghrelin uses.[24] We found no FDA approval for GHRP-6, and FDA lists it among compounding substances that may present significant safety risks.[18]

This profile covers what GHRP-6 is, what human studies found, its effect on hunger, research from Cuba on the heart and stroke, side effects, doses studied, how it compares with related peptides, and its legal status.

What is GHRP-6?

GHRP-6 belongs to a family called growth hormone secretagogues: drugs that make the body release more of its own growth hormone. In the original 1984 study, it released growth hormone in rats, monkeys, lambs and calves, but not other pituitary hormones such as LH, FSH, TSH or prolactin.[1] Growth hormone levels rose within 2 minutes of an IV dose in rats and were usually back to normal by 2 hours.[1]

GHRP-6 was the prototype for later, more potent peptides, including GHRP-2 and hexarelin. Hexarelin was made by swapping one building block of GHRP-6 (tryptophan) for a modified version.[2] When GHRP-6 was discovered, its receptor’s natural partner was unknown; that hormone, ghrelin, was identified later.[10][9]

GHRP-6 in human studies

The first human study, run by Smith Kline & French, gave 17 healthy men a 30-minute IV infusion. Growth hormone rose with the dose and peaked at 45 minutes, reaching an average of 63 micrograms per liter at 1 mcg/kg. LH, FSH, TSH and ACTH did not change, and the men tolerated it well.[3]

At Tulane University, Bowers’ team gave 18 healthy men IV doses of GHRP-6 with and without growth hormone-releasing hormone (GHRH):[4]

  • Peak growth hormone climbed from 7.6 to 68.7 micrograms per liter as the dose rose from 0.1 to 1 mcg/kg.
  • Low doses of GHRP-6 combined with GHRH released more growth hormone than the two effects added together.
  • Prolactin and cortisol rose about twofold, but only at the highest dose.

That synergy became a hospital test. In a 250-person study led from Belgrade, GHRH plus GHRP-6 separated adults with growth hormone deficiency from healthy adults better than the insulin tolerance test, the usual standard.[6] A Hamburg study found GHRP-6 alone or combined with GHRH as accurate as the insulin test in 20 patients.[7]

In Havana, researchers measured GHRP-6 levels in nine healthy men after single IV doses. Its elimination half-life was about 2.5 hours, and blood levels rose in proportion to the dose.[5]

GHRP-6 and hunger

Hunger is GHRP-6’s best-known effect. Injected directly into the brains of rats, it triggered eating in a dose-related way, separately from its effect on growth hormone.[8] The receptor it activates is the one ghrelin uses: in a London study, an IV ghrelin infusion made all nine volunteers eat more at a buffet, by 28% on average.[9] A 2026 review describes appetite stimulation as a consistent effect of GHRP-6.[24]

We did not find a controlled human feeding study of GHRP-6 itself. The closest evidence is for its successor, GHRP-2, which increased food intake by about a third in healthy men; see our GHRP-2 profile.

Cardioprotection and stroke research in Cuba

Researchers at Cuba’s Center for Genetic Engineering and Biotechnology (CIGB) have studied GHRP-6 as a protective drug for the heart and brain:

  • Heart attack model (pigs): pigs given GHRP-6 during a 1-hour blocked coronary artery had 78% less dead heart muscle than pigs given saline.[13]
  • Chemotherapy damage (rats): GHRP-6 given alongside the cancer drug doxorubicin prevented heart enlargement and loss of pumping function.[14]
  • Stroke (people, with EGF): in a 36-patient phase I/II trial, GHRP-6 combined with epidermal growth factor (EGF) was judged safe, with signs of better recovery.[15] The larger phase III COURAGE-2 trial in 188 patients, published in 2026, missed its main goal of reducing disability at 6 months. A subgroup with severe strokes did better, which the authors say warrants further studies in that group.[16]

The heart results come from animals. We found no published controlled trial of GHRP-6 in people having a heart attack.

GHRP-6 side effects

In short hospital studies, single doses were generally well tolerated:

  • Flushing: the only side effect noted in the Hamburg test study.[7] The 250-person diagnostic study reported no adverse events.[6]
  • Cortisol and prolactin: both roughly doubled at 1 mcg/kg IV.[4]
  • Blood sugar: FDA cites a potential effect on cortisol and higher blood glucose from reduced insulin sensitivity.[18]
  • Hunger: expected from its action on the ghrelin receptor.[8][24]
  • Stroke trial: serious adverse events occurred in 30 of 95 treated patients and 18 of 93 on standard care; none were judged treatment-related.[16]

FDA also warns that compounded GHRP-6 may trigger immune reactions for certain routes of administration because the peptide can clump and carry impurities.[18] Long-term human safety data do not exist.

GHRP-6 dosage: what has been studied

SettingDose
Healthy men, single IV bolus0.1 to 1 mcg/kg[4]
Diagnostic test (with GHRH 1 mcg/kg)1 mcg/kg IV once[6]
Pharmacokinetic study, Cuba100, 200 or 400 mcg/kg IV once[5]
Stroke trials, with EGF3.5 or 5 mg IV twice daily for 7 days[15][16]
US clinic records (with GHRP-2 and sermorelin)100 mcg three times daily[17]

The US clinic data come from a retrospective chart review: 14 men on testosterone who took a GHRP-6, GHRP-2 and sermorelin combination saw IGF-1 rise from about 160 to 239 ng/mL. It reported hormone levels, not muscle, fat or safety outcomes.[17] Doses promoted online come from forums and sellers, not trials. For converting milligrams to syringe units, see our peptide calculator.

GHRP-6 vs GHRP-2, hexarelin and ipamorelin

  • GHRP-2 and hexarelin were developed as stronger versions of GHRP-6. In a head-to-head study in Turin, the two released similar amounts of growth hormone and similarly raised prolactin, ACTH and cortisol.[11]
  • Ipamorelin released growth hormone about as well as GHRP-6 in pigs but, unlike GHRP-6, did not raise ACTH or cortisol.[12]
  • MK-677 hits the same receptor but is a pill rather than an injection.

Our GHRP-2 vs GHRP-6 vs hexarelin comparison lays these out side by side, and more compounds are on our growth hormone peptides page.

What users report

  • Not approved: we found no FDA approval for GHRP-6.
  • Outsourcing facilities (503B): FDA placed GHRP-6 in category 2, substances that may present significant safety risks, on September 29, 2023.[18]
  • Traditional pharmacies (503A): FDA’s May 2026 list puts GHRP-6 in category 3, substances nominated without adequate support.[19] Category 3 substances are not eligible for the interim policy under which FDA does not intend to take action against pharmacies compounding category 1 substances.[20]
  • Advisory committee: GHRP-6 was not on the agenda of FDA’s October 2024 compounding advisory meeting, which considered ipamorelin, ibutamoren (MK-677), kisspeptin-10 and L-theanine for the 503A list.[21]
  • Banned in sport: WADA lists GHRP-6 by name among growth hormone-releasing peptides, prohibited at all times.[22] A Moscow anti-doping lab found GHRP-6 mostly unchanged in urine for about 23 hours after a nasal dose and added it to routine testing.[23]

This is general information, not legal advice; rules differ by country and change over time.