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Full disclaimerGHRP-2 vs GHRP-6
Peptide Schedule Research TeamReviewed Apr 202615 Citations
Side-by-side comparison of dosage, benefits, and side effects.
A 38% decline in peak GH response from day one to day five. That finding from a Ghigo et al. study of healthy adults dosed at 100 mcg/day subcutaneous (PMID 9820615) shaped how experienced users run GHRP-2 today. GHRP-2, also called pralmorelin (CAS 158861-67-7), is a synthetic hexapeptide growth hormone secretagogue. It binds GHS-R1a on pituitary somatotrophs, mimicking ghrelin to trigger a rapid, dose-dependent GH pulse. Compared to GHRP-6, it produces a stronger GH spike per unit dose with less appetite stimulation and lower cortisol and prolactin elevation. Compared to ipamorelin, the GH output is higher but comes with mild hormonal side effects that ipamorelin avoids. The practical community protocol runs 100 to 200 mcg subcutaneous two to three times daily on an empty stomach, co-injected with CJC-1295 (no DAC) for complementary GHRH + GHRP stimulation. That combination produces two to three times the GH pulse of either peptide alone, according to consistent user reports across hundreds of Reddit threads. Cycling is mandatory: 5 days on, 2 days off within each week, plus 8 weeks on, 4 weeks off for the gross cycle. Japan's PMDA approved GHRP-2 (brand name GHRP Kaken 100) in 2004 as a single-dose IV diagnostic agent for GH deficiency. No country has approved it therapeutically. Over 200 PubMed papers cover its pharmacology, but most are mechanistic or short-term. No long-term therapeutic RCT exists for the doses the community uses. The evidence base is strong on mechanism and acute pharmacology; it's thin on multi-month safety at 100 to 300 mcg SC daily.
View full guide →GHRP-6 (Growth Hormone Releasing Peptide-6, CAS 87616-84-0) is a synthetic hexapeptide that binds the growth hormone secretagogue receptor (GHS-R1a) at the pituitary gland. It produces a bigger GH pulse than ipamorelin, but the trade-offs are real. Gonzalez and colleagues characterized its pharmacokinetics in nine healthy male volunteers using IV administration (PMID 23099431), landing on a distribution half-life of 7.6 minutes and an elimination half-life around 2.5 hours. The commonly cited plasma half-life sits at roughly 20 minutes. What separates GHRP-6 from cleaner secretagogues like ipamorelin is its ghrelin mimicry. GHS-R1a is the ghrelin receptor, so agonism there doesn't just release GH. It also triggers orexigenic signaling that makes appetite spike within 20 minutes of injection. Cortisol and prolactin both tick up slightly as well, though these elevations stay mild at standard doses (100 mcg) according to neuroendocrine data from Frieboes and colleagues (PMID 10336729). Community adoption across thousands of users on r/Peptides and bodybuilding forums has been consistent for over a decade. The top protocol pairs 100 mcg GHRP-6 with 100 mcg CJC-1295 No DAC (Mod GRF 1-29), injected two to three times daily on an empty stomach. Users report improved sleep, faster recovery, and lean mass accrual over 8 to 12 week cycles. No randomized controlled trials exist for body composition outcomes in healthy adults; the evidence base for performance use relies on GH-stimulation data extrapolated through community experience.
View full guide →At a Glance
| Attribute |  GHRP-2 |  GHRP-6 |
|---|---|---|
| Category | Growth Hormone | Growth Hormone |
| Safety Grade | B | B |
| Half-Life | ~33 min | ~20 min |
| Route | Subcutaneous | Subcutaneous |
| Vial Sizes | 5mg | 5mg |
| Beginner Dose | 100mcg Daily | 100mcg Daily |
| Moderate Dose | 200mcg 2x Daily | 200mcg 2x Daily |
| Aggressive Dose | 200mcg 3x Daily | 300mcg 3x Daily |
| Dosing Source | Community | Community |
| Side Effects | Receptor desensitization is the most clinically documented concern. Ghigo et al. showed a 38% drop in peak GH response from day one to day five at 100 mcg/day subcutaneous in healthy adults (PMID 9820615). This is not a theoretical risk; it's measured and reproducible. Without cycling (5 days on, 2 days off minimum), the peptide loses a third of its effectiveness within a week. Users who skip cycling waste product and lose the GH output they're paying for. Cortisol elevation is real but transient. Popovic et al. (PMID 9285939) documented mild ACTH and cortisol spikes post-injection that return to baseline within two to three hours. At standard doses (100 to 200 mcg once or twice daily), this rarely causes symptoms. At three times daily advanced protocols, cumulative cortisol burden can become clinically relevant: watch for disrupted sleep, irritability, or stubborn fat gain around the midsection. Get an AM cortisol lab at week eight if running the advanced protocol. Prolactin elevation follows a similar pattern: mild, transient, dose-dependent. Symptomatic hyperprolactinemia (libido changes, gynecomastia) is uncommon at standard doses but warrants lab work if symptoms appear. The prolactin burden is lower than hexarelin but higher than ipamorelin. Appetite increase hits 20 to 30 minutes after injection. GHRP-2 mimics ghrelin at GHS-R1a, and ghrelin is the hunger hormone. The effect is significantly less intense than GHRP-6 but more pronounced than ipamorelin. For cutting protocols, this can be disruptive. Shifting the bedtime dose to three or more hours after dinner (still fasted) helps manage it. Water retention and mild edema are GH-class effects, not specific to GHRP-2. Expect some puffiness in the first two to four weeks that stabilizes. Injection-site reactions include transient tingling and dizziness lasting 5 to 15 minutes post-injection. These are common, benign, and tend to diminish over the first week. Carpal tunnel symptoms (hand tingling, grip weakness) signal excessive GH-mediated fluid retention. Reduce dose or frequency immediately. If symptoms persist beyond one week at a lower dose, discontinue for a minimum of four weeks. GH antagonizes insulin action, and GHRP-2's cortisol co-elevation compounds this effect. Monitor fasting glucose at baseline and at weeks four and eight. Pre-diabetic individuals should check weekly. A fasting glucose above 125 mg/dL warrants dose reduction and medical review. Contraindications: active cancer or history of malignancy (GH promotes cell proliferation), uncontrolled diabetes or diabetic retinopathy, pregnancy or breastfeeding, active pituitary tumors, and known hypersensitivity to pralmorelin. No human data exists on multi-month subcutaneous dosing safety at the doses the community uses. | The most serious concern with GHRP-6 is its effect on blood glucose regulation. Growth hormone directly opposes insulin action, and GHRP-6 compounds this problem by driving appetite-fueled caloric surpluses that can push fasting glucose upward. Anyone with uncontrolled diabetes, insulin resistance, or prediabetes should treat this as a hard contraindication. Fasting glucose monitoring every four weeks during a cycle isn't optional at this dosing level. Cortisol elevation is the second concern worth weighing carefully. GHRP-6 mildly raises ACTH and cortisol, confirmed by Frieboes and colleagues in their neuroendocrine study (PMID 10336729). At 100 mcg once daily, this is generally subclinical. At 200 to 300 mcg three times daily, the cumulative cortisol load becomes meaningful enough to potentially impair recovery, sleep quality, and fat metabolism. Users running aggressive protocols should check morning cortisol at week four. Prolactin elevation also occurs, more so than with ipamorelin but less than hexarelin. At aggressive doses, some users report symptoms consistent with raised prolactin. Baseline and week-four prolactin checks are warranted if dosing exceeds 200 mcg per injection. Published side effects from the pharmacokinetic literature include tingling, facial flushing, dizziness, and transient warmth, all of which represent normal GH-pulse effects and typically resolve within 30 to 60 minutes. Community reports confirm these; they're predictable and dose-dependent. Water retention is common at higher doses (200 to 300 mcg range). Users report two to four pounds of water weight during peak dosing weeks. This resolves within one to two weeks of dose reduction or cessation. The appetite effect deserves its own warning. At 300 mcg, hunger becomes genuinely difficult to manage. This is a ghrelin mimetic doing exactly what ghrelin does. Users attempting to use GHRP-6 during a caloric deficit generally abandon the attempt; this peptide is a bulking tool. Injection site reactions (redness, mild irritation) are possible with any subcutaneous peptide. Pregnancy and breastfeeding are absolute contraindications. No human safety data exists for these populations. |
Key Differences
- GHRP-2 produces stronger GH release per dose; GHRP-6 causes more appetite stimulation via ghrelin.
- GHRP-6 raises cortisol and prolactin more than GHRP-2.
- GHRP-2 is preferred when hunger side effects are unwanted; GHRP-6 is preferred when appetite stimulation is desired.
- Both have similar half-lives and dosing frequencies.
When to Choose GHRP-2
- You want maximum GH release with fewer side effects
- Appetite stimulation is unwanted (cutting/weight loss phases)
- You want to minimize cortisol and prolactin elevation
- Clean GH release is the priority
When to Choose GHRP-6
- You want appetite stimulation (bulking/gaining weight)
- Enhanced hunger signaling is a desired benefit
- You're in a mass-gain or recovery phase
- Cost is a factor (GHRP-6 is often cheaper)
Can You Stack GHRP-2 + GHRP-6?
GHRP-2 and GHRP-6 target the same receptor (GHS-R). Stack either one with CJC-1295 instead for a combined GHRH + GHRP effect.
Dosage Calculators
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