100 to 300 mcg under the skin, two to three times daily
What was studied
1 mcg/kg into a vein, about 80 to 100 mcg
The gap
Convention lands on a studied dose
How long it lasts
About 2.5 hours, give or take 1.1, and that figure comes from one route only: nine healthy men given single doses into a vein at 100, 200 and 400 micrograms for every kilogram of body weight. I found no study in a person of the route almost everybody actually uses, the needle under the skin, measuring where a dose goes and how fast it disappears.
What it actually is
GHRP-6 stands for growth hormone releasing peptide 6. It is a lab made chain of six of the small building blocks that proteins are made from, and short chains like this are called peptides. The six read His-D-Trp-Ala-Trp-D-Phe-Lys-NH2. What is unusual about it is the order the discoveries came in. Bowers and colleagues described the compound in the journal Endocrinology in 1984, in rats, monkeys, lambs, calves and chicks, and at that point nobody knew what it latched onto. The docking point it presses, called the growth hormone secretagogue receptor, was not cloned until 1996, by Howard and colleagues, who found it by chasing these synthetic peptides backwards. Ghrelin, the hormone the body makes for that same docking point, was not identified until Kojima and colleagues got there in 1999, fifteen years after the peptide. Somebody built a doorbell, then somebody found the door it rang, then somebody worked out who had been pressing it. The field calls that reverse pharmacology.
What it is supposed to do
It presses the docking point that ghrelin, the body's own hunger hormone, was later found to use, and the small gland at the base of the skull answers by releasing a pulse of the body's own growth hormone. That much is not in doubt and it was measured early. In 18 normal men given single doses into a vein in 1990, peak growth hormone in the blood was 1.2 micrograms in a litre on the dummy injection and then 7.6, 16.5 and 68.7 as the dose climbed through 0.1, 0.3 and 1.0 micrograms for every kilogram of body weight. The body's own hormone is the stronger signal: in six normal subjects given ghrelin and GHRP-6 at the same 1 microgram per kilogram into a vein, ghrelin peaked at 39.9 micrograms per litre of growth hormone against 18.4. The follow on marker moves too, once. The only published rise in insulin like growth factor 1 on GHRP-6 alone came out of a 34 hour drip in nine healthy young men, a 1 microgram per kilogram dose into a vein followed by 1 microgram per kilogram every hour, where the size of the growth hormone pulses roughly doubled and that blood marker went from 252 to 312 micrograms in a litre.
What people take it for
The article does not survey what buyers say they are after, so what follows is what it could and could not find. The effect people buy it for is hunger, and that is the one it went looking for and did not find: I could not find a single published human study that measured appetite, hunger ratings or food intake after GHRP-6. You can run the search yourself on PubMed, GHRP-6 with appetite or food intake, which returned 98 records, all animal work, reviews, or studies of a related compound written [D-Lys3]-GHRP-6, which is the blocker rather than the drug. Every human figure in circulation about the hunger, the share of users it hits, when it starts and how long it lasts, is vendor copy with nothing under it. The hunger evidence that does exist is in rodents: female Wistar rats given 250 micrograms per kilogram under the skin twice a day for two weeks ate more for up to seven hours after a single injection and put on 15 percent more weight in the fat pad in the groin and 20 percent in the fat pad around the gut. The useful half of that study is its control condition. In rats whose adrenal glands had been removed and who were given no replacement stress hormone, the appetite effect disappeared at every time point, so background stress hormone has to be present for the hunger to happen. Beyond hunger, I could not find a human trial testing it for body composition, fat loss, recovery or ageing.
The dose question
What circulates
100 to 300 mcg under the skin, two to three times daily
What was studied
1 mcg/kg into a vein, about 80 to 100 mcg
Bowers 1990, 18 normal men, and the same dose and route reused exactly in five later studies
Lands on a studied dose
The number matches, and unusually for this reference it is traceable. Bowers 1990 set 1 mcg/kg into a vein as its top rung, Borges 1997, Pandya 1998, Muller 2001, Micic 2002 and Alaioubi 2010 all reused that dose and that route exactly, and for an 80 to 100 kg man that is 80 to 100 mcg, which lands on the flat 100 mcg the community uses. Above that bottom rung the convention keeps going, to 300 mcg an injection and 200 to 900 mcg a day. The transfer is the part I found no validation of: the published dose is a single bolus into a vein for acute provocation, the convention is repeated injection under the skin for weeks, and I found no human study measuring blood levels after an injection under the skin, no dose response by that route, and no study of repeated daily dosing under the skin of GHRP-6 alone. The one exposure under the skin on record put GHRP-6, GHRP-2 and sermorelin in at once.
Reported because it is what people use. Nothing here recommends any amount.
How long it lasts
About 2.5 hours, give or take 1.1, and that figure comes from one route only: nine healthy men given single doses into a vein at 100, 200 and 400 micrograms for every kilogram of body weight. I found no study in a person of the route almost everybody actually uses, the needle under the skin, measuring where a dose goes and how fast it disappears.
Route studied
Into a vein, in the human studies that state a route: the 18 man dose ladder in 1990, the 34 hour drip in nine young men, the half life work in nine men, and a Cuban randomised trial in 36 patients with a stroke caused by a blocked artery, which gave 3.5 or 5 milligrams into a vein twice a day for 7 days and always paired it with a second compound, epidermal growth factor, so nothing in it can be assigned to GHRP-6. Swallowing has also been through people: ten normal men took it by mouth at 30, 100 and 300 micrograms per kilogram and peak growth hormone came out at 5.2, 9.2 and 18 micrograms in a litre up that ladder, against 26 from 1 microgram per kilogram into a vein, so swallowing it works at roughly three hundred times the dose into a vein. The largest single group of people given it, 69 of them in the adrenal testing work, is a study whose route is not stated in the abstract.
Route used
Injected under the skin at home, two to three times a day on an empty stomach, in runs of 8 to 16 weeks. That is neither of the two routes that have been through people. The only exposure under the skin on record is a look back at 14 men with low testosterone, with no control group, who were taking GHRP-6 alongside GHRP-2 and sermorelin, 100 micrograms of each, three times a day for an average of 134 days, with a blood growth marker rising from 159.5 to 239.0 nanograms in a millilitre. Three compounds went in at once, so nothing in it belongs to GHRP-6 on its own.
How to check you have the right molecule
There is one check you can do yourself and it is on the weight printed on the laboratory report that came with the batch. Doping control chemists found Gly-GHRP-6 in black market products, which is this peptide with one extra building block, glycine, stuck on the front. GHRP-6 itself has a monoisotopic weight of 872.44, and glycine adds 57.02, which puts the substitute near 929.46 as a neutral molecule. Treat that 929.46 as a place to look rather than a number to certify against, because it is arithmetic on published weights rather than a figure printed in that paper. The second check is the name sitting beside the number. GHRP-2 is a different molecule sold in the same aisle, and its results are cited as though they were this one's. They are not.
Two mistakes, and both are borrowing. The first is GHRP-2, which is a different molecule. The multi month growth study people cite for GHRP-6, six children before puberty who were short of growth hormone, given stepwise doses under the skin of 0.3, 1.0 and 3.0 micrograms per kilogram a day over eight months, where growth speed rose while two blood growth markers did not, used GHRP-2. Its evidence is not this one's evidence. The vendor claim running the other way, that GHRP-6 is the dirtier of the two, rests on a comparison I could not locate: I found no human head to head against GHRP-2 on prolactin, cortisol, adrenocorticotropic hormone, the pituitary signal that drives the stress hormone cortisol, growth hormone or appetite. The second mistake is reading the hunger as proof the thing is working. Because GHRP-6 led researchers to ghrelin, it gets sold as though it were ghrelin, and in six normal subjects given both at 1 microgram per kilogram into a vein, the real hormone peaked at 39.9 micrograms in a litre of growth hormone against 18.4.
What is known about harm
This entry carries no side effect tally from any of the human studies, so what is known about harm here is thin rather than clean. What the record does carry is which hormones move and at what dose. In the 18 man study, prolactin and the stress hormone cortisol each rose about two fold above where they started, and only at the top 1 microgram per kilogram rung, while luteinising hormone, which drives the sex hormones, and thyroid stimulating hormone did not move over the first hour. That top rung is the same dose the whole convention was worked back from. The stress hormone axis moves reliably enough that GHRP-6 was trialled as a diagnostic test for a failing adrenal system: 49 patients with suspected trouble in the pituitary and adrenal glands plus 20 healthy controls, at 1 microgram per kilogram, where mean peak cortisol came out at 227 nanomoles in a litre in the group whose adrenal glands were failing against 395 in the group whose were not. For the practice people actually run, I found no study of repeated daily dosing under the skin of GHRP-6 on its own, so there is no repeated dosing safety record to report for it. It is named on the 2026 World Anti-Doping Agency Prohibited List under S2.2.4, growth hormone releasing factors, banned at all times, in and out of competition, in the more serious non-Specified tier. The United States Food and Drug Administration has it on two lists with two different answers: Category 3 on the 503A list for pharmacy compounding, dated 29 September 2023, meaning it was nominated without adequate support for the agency to evaluate it, and Category 2 on the 503B list for outsourcing facilities, updated 21 March 2025, meaning substances that raise significant safety risks, listed flatly with no route exemption. I found no evidence it is approved for human use in any jurisdiction.