GHRP-2 vs GHRP-6
There is no winner on this page. What is set side by side is the published record behind each one, which is the part the two are rarely compared on.
Both in Growth hormone
The evidence for one is routinely printed under the name of the other. The eight month growth study in six children cited for GHRP-6 used GHRP-2. Both conventions start from the same 100 mcg, and only one of those is traceable: for GHRP-6 it is a 1 mcg/kg bolus into a vein reused across six trials, while for GHRP-2 it is the Japanese diagnostic dose, approved for a single test injection into a vein, fasted, under supervision, to find out whether a pituitary works. What circulates for both is repeated injection under the skin, which is a different exposure by a route neither figure came from.
| Field | GHRP-2 | GHRP-6 |
|---|---|---|
| What a trial gave | 100 mcg, one injection into a veinThe Japanese label, marketed since February 2005: one slow injection into a vein, given fasting, for the diagnosis of growth hormone secretion deficiency. The nearest repeated dosing is Nijland, 100 mcg under the skin once daily for five days in nine healthy young men. | 1 mcg/kg into a vein, about 80 to 100 mcgBowers 1990, 18 normal men, and the same dose and route reused exactly in five later studies |
| What circulates | 100 to 300 mcg per injection under the skin, one to three times daily, most commonly 200 mcg | 100 to 300 mcg under the skin, two to three times daily |
| The gap | Above the studied dose | Lands on a studied dose |
| How long it lasts | This entry gives no half life, in any species and by any route. The nearest thing in it to a timing figure is measured in days rather than hours, and it is about the response rather than the substance: across five days of one injection a day in nine healthy young men, the peak growth hormone fell from a mean of 83 micrograms per litre on day 1 to 59 on day 3 and 51 on day 5. That is a response fading, not a measurement of how long a dose stays in the body. | 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 for the approved use, one slow injection given on an empty stomach, and into a vein again in Arvat 1997 at 1 and 2 micrograms per kilogram of body weight. Under the skin in the study that matches what people actually do, 100 micrograms once daily for five days in nine healthy young men. The two places insulin like growth factor 1 moved were both continuous rather than injected: a pump under the skin at 1 microgram per kilogram per hour for 30 days, and a drip into a vein at that same hourly rate for 21 hours in intensive care after a single injection into a vein. The appetite work used drips under the skin as well. In children, injections under the skin for eight months at 0.3 to 3.0 micrograms per kilogram per day, and dosing up the nose for 18 to 24 months. The 30 day pump paper also reports single doses of 0.1, 1 and 10 micrograms per kilogram, and its abstract describes the acute comparisons as going into a vein, specifying under the skin only for the 10 microgram per kilogram dose. | 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, one to three times a day, taken on an empty stomach and run in cycles. That is a different route and a different frequency from the only approval I could find anywhere, which is one injection into a vein, given once, under supervision. | 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. |
| Vial sizes | 5 mg | 5 mg |
The distance, stated
Above the studied dose
GHRP-2
The approval covers a single administration as a test, one slow injection into a vein given fasting, and it says nothing about the second dose. What circulates is up to three injections a day under the skin, run in cycles. The bottom of that range is the same 100 mcg as the Japanese diagnostic dose and the Nijland protocol, and I could not establish any derivation for it, beyond noting that nobody appears to have reasoned from either. Across those five days of daily injections the peak growth hormone fell from a mean of 83 mcg/L to 51, and mean serum IGF-1 did not move at all. It moved under a 30 day pump and under a drip into a vein, not under an injection.
Lands on a studied dose
GHRP-6
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.
What people get wrong
GHRP-2
Three mistakes, and the first one is the whole compound. It is reading the Japanese approval as cover for the habit. Everywhere else in this reference I am reporting the absence of safety data, and here a regulator has a printed table with percentages on it, describing what one injection into a vein does when it is given fasting, under supervision, to find out whether a pituitary works. That is the entire approved use in the one country an approval could be found in, and it says nothing about the second dose. The second is the rise in insulin like growth factor 1 that gets quoted to buyers. It is real, and it came from a pump running for 30 days and a drip running in intensive care. Under the thing people actually do, an injection under the skin, that marker did not move over five days in healthy men, over eight months in growth hormone deficient children, or over 18 to 24 months up the nose. Nobody runs a pump. The third takes about five minutes to catch: the cycling advice in circulation is credited to a 1998 paper that is not the paper linked beside it, and the paper named is a swine study of ipamorelin, in which both GHRP-6 and GHRP-2 raised adrenocorticotropic hormone and cortisol while ipamorelin did not.
GHRP-6
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.
Every figure above is carried across from each compound’s entry, which is where the citations live.
All 65 compounds on one page at what circulates vs what was studied, or pick another two to compare.