GHRP-6
Growth Hormone Releasing Peptide-6 · His-D-Trp-Ala-Trp-D-Phe-Lys-NH2
First-generation ghrelin-receptor agonist defined by its strong appetite stimulation
Overview
GHRP-6 (Growth Hormone Releasing Peptide-6) is a synthetic hexapeptide — His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 — and one of the original growth-hormone secretagogues, characterized by Cyril Bowers in the 1980s. Like ipamorelin it works through the ghrelin receptor (GHS-R1a) rather than the GHRH receptor, evoking a robust, pulsatile release of growth hormone from the pituitary. Its defining practical feature is potency at the ghrelin receptor's appetite functions: it reliably triggers intense hunger, often within about 20 minutes of injection.
Pharmacokinetically it has a brief distribution phase of roughly eight minutes and an elimination half-life on the order of 2.5 hours, so community protocols dose it one to three times daily on an empty stomach, frequently alongside a GHRH analog such as CJC-1295 so the two receptor pathways produce a larger combined pulse. The catch is selectivity: GHRP-6 is less clean than ipamorelin, and at higher doses it raises cortisol and prolactin in addition to GH. Beyond roughly 200–300 mcg per injection, additional GH release tapers off while the appetite, cortisol, and prolactin effects keep climbing, which is why most protocols cap the per-dose amount.
GHRP-6 is not an approved medicine and is banned in competition by WADA. While its ability to release GH in humans has been well documented since the 1980s, controlled outcome data for muscle gain or fat loss are thin. The dosing ranges and schedules below reflect widely-reported community practice and published receptor pharmacology, and are presented strictly as an educational research reference.
Key parameters
- Dose range
- 100–300 mcg per dose (community)
- Frequency
- 1–3× daily
- Half-life
- ~2.5 h (elimination); ~8 min distribution
- Route
- Subcutaneous
- Vial sizes
- 5 mg · 10 mg
- Regulatory status
- Not approved as a drug in any major market; research use only. Prohibited in sport by WADA under section S2 (peptide hormones / secretagogues).
Mechanism of action
Ghrelin receptor (GHS-R1a) agonism
Activates the growth-hormone secretagogue receptor on pituitary somatotrophs and the hypothalamus to evoke a strong, pulsatile pulse of endogenous growth-hormone release.
Potent appetite stimulation
Because it strongly engages the ghrelin pathway — ghrelin being the body's principal hunger signal — it produces marked, rapid-onset appetite, the hallmark that distinguishes it from the selective ipamorelin.
Non-selective endocrine activation at higher doses
Unlike ipamorelin, GHRP-6 also raises cortisol and prolactin as the dose increases, so its GH benefit comes with more off-target hormonal effects.
Complementary to GHRH signaling
Acting on the ghrelin receptor rather than the GHRH receptor, it adds to GHRH-analog stimulation when stacked, producing a larger combined GH pulse than either peptide alone.
Dosing protocol & phases
| Phase | Weeks | Dose | Notes |
|---|---|---|---|
| Initiation | Weeks 1–2 | 100 mcg per injection | Lower starting dose; at ~100 mcg or below, cortisol and prolactin elevations are generally minimal. Community-derived. |
| Titration | Weeks 3–4 | 200 mcg per injection | Stepwise increase as appetite and tolerance are gauged. |
| Maintenance | Weeks 5–12 | Up to 300 mcg per injection, 1–3× daily | Doses are spaced ≥4 hours apart (e.g. morning, midday, pre-bed) on an empty stomach; beyond ~300 mcg, extra GH release is minimal while side effects rise. |
Reconstitution guide
For educational and research reference only. Not intended for human consumption, not medical advice. Compounds discussed are sold and used for laboratory research purposes only.
5 mg vial + 3 mL bacteriostatic water
Concentration1,666.7 mcg/mL · 1.667 mg/mL
| Target dose | Draw volume | U-100 units |
|---|---|---|
| 100 mcg | 0.06 mL | 6 |
| 200 mcg | 0.12 mL | 12 |
| 300 mcg | 0.18 mL | 18 |
Keeps a 100 mcg dose at a readable 0.06 mL (6-unit) draw; a 300 mcg dose is 0.18 mL (18 units).
10 mg vial + 3 mL bacteriostatic water
Concentration3,333.3 mcg/mL · 3.333 mg/mL
| Target dose | Draw volume | U-100 units |
|---|---|---|
| 200 mcg | 0.06 mL | 6 |
| 300 mcg | 0.09 mL | 9 |
Higher-strength mix for a 10 mg vial; per-dose draws stay small but readable.
Reconstitution calculator
Pre-filled with GHRP-6's vial sizes. Adjust the water volume and target dose to see the exact draw, with warnings for doses that are hard to measure or won't fit a syringe.
At 1,666.7 micrograms per millilitre, a 100 microgram dose is 0.06 millilitres, or 6 units on a U-100 syringe, giving 50 doses per vial.
Supplies needed
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Recommended supply
GHRP-6 — research vial
From our verified partner Dynotides, with a third-party certificate of analysis per batch.
Injection supplies
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Bacteriostatic water
Diluent for reconstituting lyophilized vials.
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Insulin syringes (U-100)
0.3–0.5 mL, 29–31 G for accurate small draws.
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Alcohol prep pads
Sterile swabs for the vial stopper and site.
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Sharps container
Safe disposal of used needles.
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Storage fridge
Keeps reconstituted vials at 2–8 °C.
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Insulated travel case
Cooled, TSA-friendly case for travel.
Missed-dose guidance
With an elimination half-life of only a few hours and short-lived per-dose effects, a missed dose is simply skipped rather than taken late, and the next scheduled injection is given normally. Doses are not stacked to compensate. No approved-label guidance exists.
Side effects & safety
| Category | Effect | Trial incidence |
|---|---|---|
| Gastrointestinal | Strong hunger / increased appetiteThe hallmark effect of GHRP-6, often within ~20 minutes; markedly stronger than ipamorelin and the main practical drawback. | — |
| Fluid balance | Water retention or puffinessAssociated with GH elevation; tends to ease as exposure stabilizes. | — |
| Neurological | Transient head-rush, flushing, or tingling in the handsBrief vasodilatory and paresthetic sensations common to GHRP-class peptides. | — |
| Endocrine | Cortisol and prolactin elevation at higher dosesGHRP-6 is less selective than ipamorelin; these rise as the per-dose amount exceeds ~100–200 mcg. | — |
| Metabolic | Shifts in blood glucose / insulin sensitivityGH is counter-regulatory to insulin; relevant with frequent or higher dosing. | — |
| General | Fatigue or drowsinessSometimes reported, particularly after a bedtime dose. | — |
Clinical trials & evidence
Bowers GH-secretagogue pharmacology
Phase 1 / pharmacologyAcute · Healthy adults and preclinical models
Established that GHRP-6 evokes a potent, dose-dependent GH pulse via the ghrelin receptor — foundational work in the discovery of the GH-secretagogue class — with appetite, cortisol, and prolactin effects rising at higher doses.
Trial identifier needs verification
GHS-R / ghrelin-axis characterization
PreclinicalVaries · Animal and in vitro models
Helped define the growth-hormone secretagogue receptor (later identified as the ghrelin receptor) and the appetite-stimulating arm of its signaling; controlled human body-composition outcome data remain limited.
Trial identifier needs verification
Storage & handling
- Lyophilized
- Store the lyophilized powder refrigerated at 2–8 °C, protected from light; −20 °C is used for long-term storage, and brief room-temperature excursions during shipping are tolerated.
- Reconstituted
- After reconstitution, refrigerate at 2–8 °C, protected from light, and use within about 28 days. The solution should be clear and colorless; do not freeze, and discard if it turns cloudy.
Comparisons
| Vs. | Target | Half-life | Dosing | Efficacy | Status |
|---|---|---|---|---|---|
| Ipamorelin | Ghrelin/GHS-R (both) | ~2.5 h vs ~2 h | 1–3× daily (both) | Comparable GH pulse but far stronger hunger and more cortisol/prolactin than the selective ipamorelin | Both research-only |
| GHRP-2 | Ghrelin/GHS-R (both) | ~2.5 h vs ~30 min | 1–3× daily (both) | GHRP-2 gives more GH per mcg with less hunger; GHRP-6 is the stronger appetite stimulant | Research-only vs diagnostic approval in Japan |
| CJC-1295 (no-DAC) | Ghrelin vs GHRH | ~2.5 h vs ~30 min | 1–3× daily (both) | Complementary pathways — commonly stacked for additive GH pulses | Both research-only |
Sources & references
- [1]Bowers CY et al. Growth hormone-releasing peptide (GHRP) discovery and pharmacology (review). ↗ source
- [2]PeptideInsight. GHRP-6 (Growth Hormone Releasing Peptide-6): research evidence and safety profile. ↗ source
- [3]World Anti-Doping Agency — Prohibited List, Section S2 (peptide hormones and secretagogues). ↗ source
Frequently asked questions
Why does GHRP-6 cause so much hunger?
It is a potent agonist of the ghrelin receptor, and ghrelin is the body's primary hunger signal. The appetite effect is rapid — often within about 20 minutes — and is the main practical difference from the more selective ipamorelin, which barely affects hunger.
How is GHRP-6 different from ipamorelin?
Both release GH through the ghrelin receptor, but GHRP-6 is far less selective: it drives strong appetite and, at higher doses, raises cortisol and prolactin. Ipamorelin produces a comparable GH pulse with minimal hunger or cortisol response, which is why it has largely overtaken GHRP-6 in popularity.
Is there a ceiling on the dose?
Practically, yes. Past roughly 200–300 mcg per injection the extra GH release becomes small while the appetite, cortisol, and prolactin effects keep increasing, so most protocols cap the per-dose amount rather than pushing higher.
Related protocols
Ipamorelin
NNC 26-0161
Selective GH pulse with minimal cortisol or prolactin effect
CJC-1295 (no-DAC)
Mod GRF 1-29
Short-acting GHRH analog dosed for natural GH pulses
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For educational and research reference only. Not intended for human consumption, not medical advice. Compounds discussed are sold and used for laboratory research purposes only.