GHRP-6: benefits, side effects, hunger and what the research shows

GHRP-6 (growth hormone-releasing peptide 6) has the sequence His-D-Trp-Ala-Trp-D-Phe-Lys-NH2. Cyril Bowers and Frank Momany reported in 1984 that this small synthetic peptide released GH specifically, without releasing LH, FSH, TSH or prolactin in their experiments, and that it worked in rats, monkeys, lambs and calves. When injected once or twice daily into young rats for 9 to 25 days, it increased weight gain, and the pituitary was still fully responsive to it at the end ^[1].

Its mechanism was unknown for years. In 1996 researchers cloned the receptor that GHRP-6 and related compounds act on, the growth hormone secretagogue receptor ^[2], and in 1999 its natural ligand was identified as ghrelin, a hormone made in the stomach ^[3]. GHRP-6 is therefore the parent of a family that includes GHRP-2, hexarelin and ipamorelin.

Ask what GHRP-6 is used for and there are two different answers. In research it has been a tool for studying the ghrelin receptor and, combined with GHRH, part of a diagnostic test for growth hormone deficiency in adults ^[16]. Outside research it is sold by research peptide vendors, often labelled GHRP-6 acetate, for bodybuilding and body composition, which are uses that have never been tested in a controlled trial. The acetate in that name describes the salt form the powder is supplied in; it is the same peptide.

GHRP-6 mimics ghrelin at the GHS-R1a receptor in the pituitary and hypothalamus, triggering a pulse of GH. In healthy men, intravenous GHRP-6 raised GH in a dose-dependent way, and combining it with GHRH released more GH than the two would be expected to release separately. The authors took this synergy as evidence that GHRPs work through a system separate from GHRH ^[4]. It underlies the common practice of pairing a GHRP with a GHRH analogue such as CJC-1295 or sermorelin, though those specific combinations have not been tested in published trials.

Unlike ipamorelin, GHRP-6 is not fully selective for GH. At the highest intravenous dose in the 1990 study, prolactin and cortisol each rose about twofold ^[4], and in pigs GHRP-6 raised ACTH and cortisol where ipamorelin did not ^[5]. As a ghrelin mimetic it is also widely described as increasing appetite; this has been shown in people for GHRP-2 ^[6] but we did not find an equivalent controlled human study for GHRP-6.

Reviews of the GHRP family describe a dual site of action, on the pituitary and on the hypothalamus. The GH response is reproducible, is similar in men and women, rises from birth to puberty and declines with age, although in people in their sixties it remains larger than the response to GHRH. It is blunted by high blood glucose, free fatty acids, glucocorticoids, growth hormone itself and somatostatin ^[18].

Hunger is the effect most associated with GHRP-6, and the animal evidence for it is consistent. Injected into the brain ventricles of well-fed rats, GHRP-6 caused a dose-related increase in eating without a matching change in blood GH, which suggested that the feeding effect does not depend on GH release ^[14]. A Manchester group found that GHRP-6 given the same way increased food intake and switched on appetite-regulating areas of the hypothalamus and brainstem, and that blocking the Y1 receptor for neuropeptide Y prevented the extra eating ^[13].

The effect also appears when the peptide is injected under the skin. In rats given 250 µg/kg twice a day for two weeks, a single injection increased food intake for up to seven hours, and body weight rose compared with saline. Fat pads were 15 to 20% heavier in rats with intact adrenal glands. Removing the adrenal glands abolished the extra eating unless corticosterone was replaced, which points to a role for stress hormones in the appetite response ^[15].

In people, the closest controlled evidence comes from GHRP-2. In healthy men it increased food intake by about 36% ^[6], and in a year-long study of oral GHRP-2 in children with GH deficiency, seven of ten reported a clear increase in appetite during the first six months, without a significant change in body mass index ^[29]. We found no published controlled trial that measured hunger or food intake after GHRP-6 in humans, so the size of the effect in people is unknown. Claims that GHRP-6 causes more hunger than GHRP-2 or ipamorelin come from user reports, not from head-to-head studies.

In humans the published work measures hormones rather than clinical outcomes. Intravenous doses of 0.1, 0.3 and 1.0 µg/kg produced mean peak GH levels of 7.6, 16.5 and 68.7 µg/L in 18 healthy men ^[4]. Taken by mouth, GHRP-6 still released GH at doses of 100 and 300 µg/kg, but with only about 0.3% of the intravenous activity; in nine children with short stature and varying degrees of GH deficiency, four responded like adults and the rest had low or undetectable responses ^[7].

A 2013 Cuban phase 1 study measured GHRP-6 levels in nine healthy men after single intravenous doses of 100, 200 and 400 µg/kg. The elimination half-life was about 2.5 hours, and the amount in the blood rose roughly in proportion to dose. The authors also noted unexplained spikes in GHRP-6 concentration during the elimination phase in four of the nine volunteers ^[8].

Animal research has explored effects beyond GH. In adult female rats, 12 weeks of GHRP-6 or ipamorelin increased bone mineral content by making bones larger, not denser ^[9]. A Cuban group has studied GHRP-6 as a tissue-protective agent: in pigs with an induced heart attack, a single 400 µg/kg dose reduced infarct mass by 78% compared with saline, which the authors linked to antioxidant effects ^[10]. These findings have not been tested in human trials.

Most benefits attributed to GHRP-6 online are extrapolated from its ability to raise GH. Every human study confirms that it does release GH ^[4][7]. Reviews also report that repeated GHRP dosing raises IGF-1 in animals and humans, but that the GH response partly fades with prolonged exposure, more with continuous infusion than with intermittent doses ^[18]. No study has shown that this translates into more muscle or less fat in healthy adults.

For muscle and bodybuilding, there are no human trials of GHRP-6 measuring muscle mass, strength or performance. The muscle-related data are animal weight-gain studies ^[1][15], and in one of them part of the extra weight was fat ^[15]. A 2026 clinical review of GH-axis peptides used without prescription placed GHRP-6 among compounds with no regulatory approval for physique or performance uses and highlighted the uncertainty around claimed recomposition benefits ^[24].

For fat loss, the evidence points the other way in rats, where GHRP-6 increased fat pad weight ^[15]. No human fat-loss trial exists. The GH-axis peptide with an approved fat-related indication is tesamorelin, a GHRH analogue licensed in the US to reduce excess abdominal fat in adults with HIV-associated lipodystrophy ^[30].

For stroke, Cuban researchers have tested GHRP-6 combined with epidermal growth factor (EGF). In a phase I/II trial of 36 patients treated within 12 hours of an ischaemic stroke, EGF plus 3.5 mg or 5 mg GHRP-6 given intravenously twice daily for seven days was judged safe, and treated patients had better neurological and functional scores at 90 and 180 days ^[22]. The larger phase III COURAGE-2 trial randomised 188 patients and missed its primary endpoint: in the full population there was no difference in disability, daily functioning or survival at six months. A subgroup with severe strokes did better on treatment, which the authors said warranted further study ^[23]. The combination, not GHRP-6 alone, was tested.

For sleep, a German study gave healthy young men GHRP-6 by three routes at night. A 30 µg/kg nasal dose raised GH through the night and showed a trend towards more stage 2 sleep, while an oral dose left GH, ACTH and cortisol unchanged ^[19]. We found no human studies of GHRP-6 for skin, hair, joints or injury healing.

Human research on GHRP-6 falls into four groups: dose-response studies in healthy men ^[4], oral studies in adults and children ^[7], sleep and route studies ^[19] and a pharmacokinetic study ^[8]. A fifth group used GHRP-6 as a diagnostic tool, and the most recent work is the Cuban stroke programme ^[22][23].

The diagnostic work is the largest. In a multicentre study published in the Lancet in 2000, 125 adults with pituitary disease and 125 healthy volunteers received GHRH 1 µg/kg plus GHRP-6 1 µg/kg intravenously. Mean peak GH was 59.2 µg/L in healthy people and 4.1 µg/L in patients, a wider separation than with the insulin tolerance test, and the authors reported no side effects. They proposed a cut-off of 15 µg/L to distinguish GH deficiency ^[16].

Taken together these studies involve several hundred people, but almost all received one dose, or a few, under medical supervision. The longest human exposure we found was seven days of twice-daily intravenous infusions in hospital stroke patients, given together with EGF ^[22][23]. There are no data on months of self-injected use, which is how GHRP-6 is used outside research.

For its hormone effect, the answer is short. In the diagnostic studies blood was sampled for 120 minutes after an intravenous dose ^[16], and the pharmacokinetic study found a distribution half-life of about 8 minutes and an elimination half-life of about 2.5 hours ^[8]. In rats, food intake rose within hours of an injection ^[15].

For outcomes such as muscle, fat or recovery, there is no human timeline, because no human trial has measured them. The stroke trials assessed disability three and six months after a seven-day course in patients ^[23], which says nothing about healthy users. GHRP-6 reviews and before-and-after pictures posted online cannot separate the peptide from training, diet, other drugs or the uncertain contents of an unregulated vial.

In research GHRP-6 has been given intravenously, under the skin, into the nose, under the tongue and by mouth ^[18][19]. By mouth it works only weakly: oral GH-releasing activity was about 0.3% of intravenous activity ^[7], and in the sleep study an oral 300 µg/kg dose in enteric-coated capsules did not change GH, ACTH or cortisol, while sublingual dosing produced only a trend towards higher GH ^[19]. That is a reason for caution about capsule products sold as a GHRP-6 supplement.

The nasal route has more support. A 30 µg/kg intranasal dose raised overnight GH in healthy men ^[19]. In rats, intranasal GHRP-2 reached a bioavailability of about 50%, while nasal absorption of GHRP-6 was somewhat lower ^[20]. An anti-doping study gave GHRP-6 into the nose of one volunteer and found it was mostly excreted unchanged, detectable in urine for 23 hours ^[21]. These studies used laboratory preparations; GHRP-6 nasal spray products sold online have not been tested.

We found no published data on GHRP-6 creams or absorption through the skin. Research products are sold as a freeze-dried powder, which is reconstituted with sterile or bacteriostatic water before use.

Human studies used single intravenous doses of 0.1 to 1.0 µg/kg ^[4], oral doses of 100 and 300 µg/kg ^[7], and, in the pharmacokinetic study, intravenous doses of 100 to 400 µg/kg ^[8]. Animal studies used 0.5 mg/kg per day by infusion in rats ^[9] and 400 µg/kg in pigs ^[10]. These figures describe what researchers gave; they are not recommendations, and animal doses should not be converted into human ones. For reconstitution arithmetic, see our peptide calculator.

Questions about GHRP-6 dosage per day have no answer from controlled trials in healthy people. The only repeated human dosing we found was in the stroke trials, where patients received 3.5 mg or 5 mg intravenously twice daily for seven days alongside EGF, under hospital care ^[22][23]. The diagnostic test uses a single 1 µg/kg intravenous dose with GHRH ^[16], and the nasal sleep study used a single 30 µg/kg dose ^[19]. In rats, 250 µg/kg was injected under the skin twice daily for two weeks ^[15]. Figures presented online as a GHRP-6 dosage for bodybuilding do not come from these studies.

Vial arithmetic is only division. A 5 mg vial mixed with 2 mL of liquid holds 2.5 mg per mL, which is 25 µg in each 0.01 mL, the volume of one unit on a U-100 insulin syringe. A 10 mg vial in the same volume is twice as concentrated. The peptide calculator does the sum for any vial size, but it cannot tell you whether a vial really holds the stated amount; that is what independent third-party testing checks.

In the 1990 dose-ranging study, no adverse clinical effects or laboratory abnormalities were seen after GHRP-6 injection; the brief facial flushing reported was after GHRH, not GHRP-6 ^[4]. The known effects are hormonal: rises in prolactin and cortisol at higher doses ^[4][5]. There are no long-term human safety data, and products sold for research are not manufactured to medicine standards.

Other studies add detail. A nasal dose produced a trend towards higher ACTH in the first half of the night ^[19], and the close relatives GHRP-2 and hexarelin raised prolactin, ACTH and cortisol in healthy volunteers, with an ACTH and cortisol response similar to that from corticotrophin-releasing hormone ^[17]. Increased appetite is expected from the animal data ^[13][15]. The Lancet diagnostic study reported no side effects after a single combined dose ^[16].

A 2026 review of GH-axis peptides used without prescription lists the adverse effects reported across the class: prolactin and cortisol elevations, appetite changes, blood-sugar disturbances, fluid retention, muscle and joint pain and injection-site reactions, along with growth-promoting concerns it described as biologically plausible but unproven ^[24]. In the phase III stroke trial, serious adverse events occurred in 30 of 95 treated patients and 18 of 93 controls; the investigators judged none of them to be treatment-related ^[23].

GHRP-2 (pralmorelin) is a later analogue from the same family, and Italian researchers described GHRP-2 and hexarelin as “super-analogues” of GHRP-6 ^[17]. The peptides share an Ala-Trp-D-Phe-Lys core and differ at the start of the chain ^[31]. We found no head-to-head human trial comparing them. Peak GH figures from separate studies, such as 68.7 µg/L after 1 µg/kg GHRP-6 ^[4] and 84.6 µg/L after a 100 µg dose of GHRP-2 ^[25], used different doses, assays and volunteers, so they cannot be compared directly. Our GHRP-2 vs GHRP-6 comparison sets the two side by side.

The practical differences in the literature are these. Both raise prolactin, ACTH and cortisol as well as GH ^[4][17]. Appetite effects have been measured in people for GHRP-2 ^[6][29] but not for GHRP-6. In rats, GHRP-2 was absorbed through the nose better than GHRP-6 ^[20]. GHRP-2 has been validated in Japan as a single-dose diagnostic test for adult GH deficiency ^[25], whereas GHRP-6 was used diagnostically only in combination with GHRH ^[16]. After nasal doses in single volunteers, GHRP-2 metabolites were detectable in urine for up to 47 hours and GHRP-6 for 23 hours ^[21]. Both are named on the WADA Prohibited List ^[11].

Taking GHRP-2 and GHRP-6 together has not been studied. Both act on the same receptor; the synergy shown in human studies is between a GHRP and GHRH, which act on different receptors ^[4]. More detail on the newer peptide is in our GHRP-2 guide.

Ipamorelin was developed by Novo Nordisk as a more selective GH secretagogue. In pigs it released GH without raising ACTH or cortisol, while GHRP-6 raised both ^[5]. In rats its plasma clearance was five times lower than that of GHRP-6, and the two left the body by different routes: ipamorelin mainly in urine, GHRP-6 mainly in bile ^[20]. In one 12-week rat study both increased bone mineral content ^[9]. There is no controlled human comparison of the two for appetite, body composition or side effects. Our ipamorelin guide covers its own research.

Human growth hormone (somatropin) is the hormone itself. GHRP-6 prompts the pituitary to release the body’s own GH in a pulse, so it depends on a working pituitary. In the diagnostic study, patients with pituitary disease had a mean peak of 4.1 µg/L compared with 59.2 µg/L in healthy people ^[16], and reviews describe the response as almost absent after pituitary stalk disconnection ^[18]. Its effect is also damped by glucocorticoids and by GH itself ^[18].

The legal position differs too. In the UK somatropin is a Class C controlled drug under the Misuse of Drugs Act, which does not name GHRP-6 ^[32]. We found no study comparing GHRP-6 with HGH for bodybuilding or body composition, so comparisons of GHRP-6 vs HGH for bodybuilding online are not based on trial evidence.

Blends of a GHRH analogue with GHRP-6 are among the most searched GHRP-6 products. The rationale comes from human studies: low doses of GHRP-6 given with GHRH released more GH than either alone ^[4], and the combined GHRH plus GHRP-6 test gave mean GH peaks of about 59 µg/L in healthy adults ^[16]. Those studies used native GHRH in single intravenous doses.

What has not been studied is the combination sold online. We found no published human trial of sermorelin and GHRP-6 used together, of CJC-1295 with GHRP-6, or of Mod GRF 1-29 (explained in our CJC-1295 guide) with GHRP-6, and no data on the stability of pre-mixed blend vials. A combination would also combine side effects, since GHRP-6 raises cortisol and prolactin at higher doses ^[4]. All of these peptides are named on the WADA Prohibited List ^[11]. Our sermorelin guide covers what is known about that peptide on its own.

In healthy men given intravenous GHRP-6, the distribution half-life was about 8 minutes and the elimination half-life about 2.5 hours ^[8]. In rats it was cleared faster than ipamorelin and excreted mainly in bile ^[20]. After a nasal dose, unchanged GHRP-6 was detected in one volunteer’s urine for 23 hours ^[21]. Anti-doping laboratories have also found a glycine-extended form of GHRP-6 in black-market products ^[12].

GHRP-6 is not an approved medicine in the UK, US, Canada, Australia or New Zealand. It appears by name on the WADA Prohibited List among the GH-releasing peptides in section S2 and is banned at all times ^[11]. Anti-doping laboratories have found glycine-extended GHRP-6 in black-market products ^[12]. For national rules, see our legal status overview.

Some countries name it specifically. In Australia, GHRP-6 is listed in Schedule 4 (prescription only) of the Poisons Standard and in Appendix D, which means it must not be possessed without authority ^[27]; see Australian legal status. In New Zealand it is classified as a prescription medicine, and a May 2026 Medsafe advisory that named GHRP-6 said it is illegal to import, sell or use these unapproved peptide products ^[28]. In the US, GHRP-6 remains in the FDA’s category of bulk substances that may present significant safety risks in compounding, as of April 2026 ^[26]; see US legal status. In the UK it is not an authorised medicine and is not among the hormones controlled under the Misuse of Drugs Act ^[32]; see UK legal status.

GHRP-6 for research is sold as a freeze-dried powder, and no stability data have been published for these products. See our guides to storing peptides and bacteriostatic water.

Compare prices per milligram, check the certificate of analysis with our guide on how to read a COA, and prefer third-party tested suppliers.

Country pages list GHRP-6 prices in the UK and in the US. Because 5 mg and 10 mg vials are both common, compare the price per milligram rather than per vial; our guide to peptide prices explains how. Anti-doping analyses have found altered GHRP analogues in seized products ^[12], so it is worth reading how to spot a fake peptide supplier before ordering.