GHRP-2
A ghrelin-receptor agonist that triggers a growth hormone pulse from the pituitary.
Approved in Japan — but only as a single 100 μg intravenous dose for DIAGNOSING growth hormone deficiency, not as a treatment [6]. The one chronic human study, 8 months in 6 children, raised GH but left IGF-I unchanged [5].
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Suggested dose
100 mcg
Compound profile
GHRP-2 scientific & efficacy data
Growth Hormone
Peptide profile
Approved diagnostic agent in Japan; no treatment approval anywhere
GHRP-2
100 mcg · Single dose (approved diagnostic use)
Molecular formula
C45H55N9O6
- Mol. weight
- 817.97 g/mol
- CAS number
- 158861-67-7
- PubChem
- 6918245
- Developed · 1991
- Cyril Y. Bowers
Tulane University
Amino acid sequence
D-Ala-D-β-Nal-Ala-Trp-D-Phe-Lys-NH2GH Release
This part is real and well documented. GHRP-2 acts on the growth hormone secretagogue receptor and produces a reproducible GH pulse — reliably enough that Japan approves a single 100 μg intravenous dose as a diagnostic test, with a peak below 15 μg/L taken as evidence of deficiency [6]. The pulse is brief: in 8 months of daily dosing, each injection's effect faded with little carry-over later in the night [5].
Recovery Speed
Not demonstrated, and the usual justification does not hold. Recovery claims run through IGF-1, but in the only chronic human study — 6 children dosed for 8 months — serum IGF-I and IGFBP-3 did not increase at any dose [5]. No trial has measured training recovery, tissue repair or strength with GHRP-2 in healthy adults.
Sleep Quality
No human trial of GHRP-2 has measured sleep. The association comes from growth hormone being released during slow-wave sleep, which is a reason to inject at night rather than evidence of an effect on sleep itself. What has been measured is appetite: food intake rose 33.5% above placebo at the higher infusion rate [7].
Dosing
How much GHRP-2 do I take?
100 mcg · single dose, once — this is a diagnostic test · intravenous
100 mcg
Single dose, once — this is a diagnostic test
Covers all 3 documented dose levels · 2 administration routes · timing · dose-adjustment guidance.
Every documented dose level
| Phase | Dose | Frequency | Route |
|---|---|---|---|
| One administration | 100 mcg | Single dose, once — this is a diagnostic test | Intravenous |
| 2 months per dose level, 8 months in total | 0.3 – 3 mcg/kg/day | Once daily | Subcutaneous |
| Undefined — no trial has run this schedule | 100 – 300 mcg per dose | 1-3 times daily (community practice) | Subcutaneous |
Suitability
Is GHRP-2 right for me?
Best for growth hormone optimization & muscle building
Best for
Natural Growth Hormone Optimization
GHRP-2 excels at stimulating your pituitary to release more of your own growth hormone. Unlike synthetic HGH, it works with your body's natural feedback systems, creating more physiological GH pulses that mimic what your body did when you were younger.
Recovery and Muscle Building
Athletes and fitness enthusiasts love GHRP-2 for its ability to speed up recovery between workouts. The elevated GH and IGF-1 levels help repair muscle tissue faster, reduce soreness, and support lean muscle growth—especially when combined with proper training and nutrition.
Deep Sleep Enhancement
One of the most noticeable effects users report is dramatically improved sleep quality. GHRP-2 taken before bed can enhance deep sleep phases, which is when your body does most of its repair work. Many users report waking up feeling more refreshed and recovered.
Anti-Aging and Vitality
As we age, natural GH production declines significantly. GHRP-2 helps restore more youthful GH levels, which can translate to better skin elasticity, improved energy, enhanced recovery capacity, and that overall feeling of vitality that tends to fade with age.
Appetite Stimulation
Unlike many peptides that suppress appetite, GHRP-2 is known for increasing hunger. This makes it ideal for hard-gainers trying to build muscle or anyone who struggles to eat enough calories. The appetite boost typically kicks in within 20-30 minutes of injection.
Consider alternatives if
Do not use if
Use with caution if
Not sure?
Compare GHRP-2 with similar peptides to find the best fit for your goals.
Administration
How do I use GHRP-2?
Intravenous (approved diagnostic use) · Subcutaneous injection
Route
Subcutaneous injection into fatty tissue
Best sites
Covers reconstitution · step-by-step technique · storage · a sample daily schedule.
Safety
Is GHRP-2 safe?
3 common side effects · 2 serious
The largest measured effect in humans is on appetite, and it is not small: in 19 adults, food intake rose 10.2 ± 3.9% at 0.1 mcg/kg/hour (p=0.011) and 33.5 ± 5.8% at 1 mcg/kg/hour (p<0.001) against placebo, with obese participants responding as much as lean ones [7].
The Japanese diagnostic label lists abdominal rumbling, leukocytosis, a feeling of warmth, low blood pressure, nausea, gastric discomfort, abdominal distension, drowsiness and rhinorrhoea as adverse reactions — but that label covers a single 100 μg intravenous dose, not repeated use [6].
In 6 growth-hormone-deficient children given 0.3 to 3.0 mcg/kg/day for 8 months, no side effects or toxicities were observed, in a cohort far too small to detect anything uncommon [5].
One adverse signal from longer infusion: in critically ill men, GHRP-2 given alone at 1 mcg/kg/hour for 5 days raised serum lactate and white cell count by day 5, which the fuller hormonal replacement in the same trial did not [8].
GHRP-2 has one regulatory approval in the world, in Japan, for a single intravenous dose used to diagnose growth hormone deficiency [6]. No regulator has reviewed it as a treatment, so there is no approved safety profile for taking it repeatedly.
The human literature is dominated by acute pituitary-physiology studies — single boluses and short infusions in small groups of volunteers, largely from Bowers and Veldhuis. Chronic dosing evidence is one study in 6 children over 8 months, where IGF-I did not rise [5].
There is no trial in healthy adults taking it for body composition, no long-term safety data, and no cancer-risk data for a compound that raises GH.
Less common
These typically resolve with continued use or dose adjustment.
Common side effects · experienced by some users
Substantially increased food intake
The largest measured human effect. In 19 adults, ad libitum food intake rose 10.2 ± 3.9% at 0.1 mcg/kg/hour and 33.5 ± 5.8% at 1 mcg/kg/hour against placebo, dose-dependently, and obese participants responded as much as lean ones [7]. Appetite before the meal was higher while fullness afterwards was unchanged — it drives starting to eat, not stopping.
Management: Treat this as the primary effect to plan around, not a footnote. If the goal is fat loss, a 33% rise in intake works directly against it.
Gastrointestinal effects
Abdominal rumbling, nausea, gastric discomfort and abdominal distension are all listed as adverse reactions on the Japanese diagnostic label, from a single 100 μg intravenous dose [6].
Management: Reported after a single dose; no management is specified on the label.
Feeling of warmth, drowsiness, runny nose
All three are listed adverse reactions on the Japanese label [6].
Management: Transient on the label's account.
Stop and seek help if
- Signs of allergic reaction (rash, swelling, difficulty breathing)
- Persistent carpal tunnel symptoms (numbness, tingling, weakness in hands)
- Significant blood sugar elevation or difficulty managing diabetes
- Pregnancy confirmed or suspected
- Development of any new medical condition—consult your provider
- Severe or persistent side effects not improving with dose reduction
Always consult with a healthcare provider before stopping or if you experience any concerning symptoms. This information is for educational purposes and should not replace professional medical advice.
With other peptides
- Safe:CJC-1295 — Excellent synergy—combining GHRP with GHRH amplifies GH release 5-10x. Can inject together.
- Caution:Ipamorelin — Both are GHRPs—using together is redundant and may cause excessive appetite stimulation.
- Caution:GHRP-6 — Both are GHRPs—do not stack together. Choose one based on appetite preference.
- Safe:Sermorelin — Good synergy as a GHRH analog. Can be combined for enhanced GH release.
- Safe:BPC-157 — Safe to combine for recovery benefits. Different mechanisms, no interactions.
With medications
- Caution:Insulin — GH has anti-insulin effects. May need insulin dose adjustment. Monitor closely.
- Caution:Diabetes medications — May affect blood sugar control. Monitor glucose levels carefully.
- Caution:Corticosteroids — Both affect cortisol/HPA axis. Use with caution and medical supervision.
- Safe:Thyroid medications — GH can affect thyroid hormone conversion. Monitor thyroid levels.
With supplements
- Safe:Arginine — May enhance GH release when taken together. Safe combination.
- Safe:Glutamine — May support GH release. Safe to combine.
- Safe:Melatonin — Both taken before bed. May have additive sleep benefits.
- Safe:Protein supplements — Essential for muscle building goals. Take protein 30+ minutes after peptide injection.
Effectiveness
How do I know GHRP-2 is working?
Approved diagnostic agent in Japan; no treatment approval anywhere · first signs week 1-2
Evidence level
Approved diagnostic agent in Japan; no treatment approval anywhere
Regulatory status
Not FDA approved
Approved in Japan as 注射用GHRP科研100 (pralmorelin hydrochloride, Kaken Pharmaceutical) for the diagnosis of growth hormone deficiency only — a single 100 μg intravenous dose. There is no treatment approval for GHRP-2 in any country.
Onset of effects
Rapid
(hours to days)
How it works
Your pituitary gland naturally releases growth hormone in pulses throughout the day, especially during deep sleep.
GHRP-2 works by mimicking a hormone called ghrelin, which tells your pituitary to release more GH. Think of it like pressing the 'release GH' button more often and more forcefully.
Unlike injecting synthetic GH directly, GHRP-2 works with your body's natural systems—your pituitary still does the work, it just does more of it. This creates more natural, pulsatile GH release patterns similar to what you had when you were younger.
The deeper mechanism
GHRP-2 (Growth Hormone Releasing Peptide-2) is a synthetic hexapeptide that acts as a potent GH secretagogue through activation of the growth hormone secretagogue receptor (GHS-R1a), the same receptor targeted by endogenous ghrelin.
Upon binding, GHRP-2 stimulates pituitary somatotrophs to release stored GH in a pulsatile fashion.
Unlike GHRH which acts through the GHRH receptor, GHRP-2 amplifies GH release through a complementary pathway, explaining the synergistic effect when both peptide classes are combined (5-10x amplification).
GHRP-2 also stimulates hypothalamic GHRH release and suppresses somatostatin tone, further enhancing GH output. Additionally, it activates ACTH release from corticotrophs, causing transient cortisol elevation.
The peptide has a plasma half-life of 15-60 minutes, but its effects on GH pulsatility persist longer. Downstream effects include elevated IGF-1 synthesis in the liver and target tissues, mediating many of the anabolic and regenerative benefits attributed to GH.
What to expect
Week 1-2
What you might notice
- Increased appetite within 20-30 minutes of each injection
- Possibly deeper sleep and more vivid dreams
- Mild water retention or puffiness
- Getting used to the injection routine
What's normal
- Hunger increase is expected and often significant
- Sleep improvements may be noticeable quickly
- Some water weight gain is common
- Flushing or warmth after injection
What's next
- Continue consistent dosing schedule
- Track sleep quality and recovery
- Note any side effects to discuss dose adjustments
- Maintain fasted state for each injection
Week 3-4
What you might notice
- More consistent sleep improvements
- Faster recovery between workouts
- Possible subtle improvements in skin quality
- Appetite effects may stabilize somewhat
What's normal
- Water retention often decreases as body adapts
- Energy levels may improve
- Hunger remains elevated but becomes more manageable
- Full GH benefits take time to manifest
What's next
- Consider adding GHRH peptide if seeking maximum results
- Assess tolerance and adjust dose if needed
- Continue tracking progress and recovery
- Ensure nutrition supports your goals
Week 5-8
What you might notice
- More noticeable improvements in body composition
- Enhanced workout performance and recovery
- Skin may appear more youthful and elastic
- Consistent sleep quality benefits
What's normal
- Changes are gradual—not overnight transformations
- Results depend heavily on diet and training
- Some side effects may diminish with adaptation
- GH benefits compound over time
What's next
- Continue at effective dose
- Consider blood work to check IGF-1, glucose levels
- Evaluate whether to continue beyond 8 weeks
- Maintain consistent injection schedule
Week 9-12+
What you might notice
- Significant cumulative improvements in recovery and body composition
- Sustained energy and vitality improvements
- Continued sleep quality benefits
- Hair, skin, and nail improvements possible
What's normal
- Benefits plateau at optimal levels
- Body adapts to elevated GH—results maintain rather than accelerate
- Some users cycle off for 4-8 weeks before resuming
What's next
- Evaluate results and decide on continuation
- Consider cycling off to maintain pituitary sensitivity
- Get follow-up blood work if continuing long-term
- Maintain healthy lifestyle habits during any break
Signs it's working
Sleep and Recovery
- Falling asleep faster and sleeping more deeply
- Waking up feeling more refreshed and rested
- More vivid or memorable dreams
- Reduced muscle soreness after workouts
- Faster recovery between training sessions
Body Composition
- Gradual increase in lean muscle mass
- Reduction in stubborn body fat over time
- Improved muscle fullness and definition
- Better workout pumps and vascularity
- Clothes fitting differently (more muscle, less fat)
General Vitality
- Improved overall energy levels
- Better skin elasticity and quality
- Stronger hair and nails
- Enhanced sense of well-being
- Increased appetite (confirms peptide is working)
Not seeing results? Common reasons
- Expecting an IGF-1 driven effect. In the only chronic human study — 6 growth-hormone-deficient children dosed for 8 months — serum IGF-I and IGFBP-3 did not increase at any dose [5]
- Expecting a body-composition result that has never been measured. No trial has tested GHRP-2 for muscle, fat, strength or recovery in healthy adults; the percentages that circulate are from rats
- Eating more without noticing. Food intake rose 33.5% above placebo at 1 mcg/kg/hour in 19 adults, and appetite before meals was higher while fullness afterwards was unchanged [7]
- A brief pulse rather than a sustained level. GH profiles showed each injection's effect faded with little carry-over later in the night, which is why the authors concluded a longer-acting formulation would be needed for therapy [5]
- Material of unknown identity or purity. The only regulated product is a Japanese diagnostic vial [6]; everything else is unverified
Key research
Clinical trials
GHRP-2 tested in people
No registered clinical trial of GHRP-2 was found in the public registries.
That does not mean nobody has studied it — laboratory and animal work is not registered anywhere. It means no study has been declared in advance where regulators and the public can see it, so there are no stated endpoints and no results anyone is obliged to report.
Questions
Frequently asked about GHRP-2
What's the difference between GHRP-2 and Ipamorelin?
Both are GH-releasing peptides, but GHRP-2 is more potent and causes significant appetite increase, while Ipamorelin is gentler with minimal hunger effects. GHRP-2 also stimulates cortisol and prolactin release, whereas Ipamorelin is more selective for GH only. Choose GHRP-2 if you want maximum GH release or need appetite stimulation; choose Ipamorelin for a cleaner, more targeted approach.
Why do I need to take GHRP-2 on an empty stomach?
The Japanese label does specify fasted administration for the diagnostic dose [6], so the instruction itself is sourced. The usual explanation — that food blunts the GH response — has not been tested for GHRP-2 in a published trial, so treat the reason as plausible rather than demonstrated. Note the awkward part: the compound raises food intake by up to a third [7], so fasted dosing and its main pharmacological effect pull in opposite directions.
Can I combine GHRP-2 with other peptides?
Yes, but strategically! GHRP-2 works best when combined with a GHRH peptide like CJC-1295 or Sermorelin—this combination can amplify GH release 5-10 times compared to either alone. However, don't combine GHRP-2 with other GHRPs like Ipamorelin or GHRP-6 as they compete for the same receptor.
How long until I see results from GHRP-2?
It depends entirely on what you are counting as a result, and for most of them the honest answer is that nobody has measured it. The GH pulse is immediate and reliable enough to diagnose on: Japan's approved test samples blood at 15, 30, 45 and 60 minutes after a single 100 mcg intravenous dose [6]. Appetite responds within the same session — food intake at a buffet lunch rose 33.5% above placebo during a 270-minute infusion [7]. Beyond that: in 6 children dosed for 8 months, growth velocity improved but IGF-I never rose [5], and no trial has ever measured muscle, fat, strength, recovery or sleep with GHRP-2 in healthy adults.
Will GHRP-2 make me hungry all the time?
It will make you eat more, and the effect has been measured rather than guessed. In 19 adults given a subcutaneous infusion double-blind against placebo, ad libitum food intake rose 10.2% at 0.1 mcg/kg/hour and 33.5% at 1 mcg/kg/hour — dose-dependent, and just as strong in the obese participants as the lean ones [7]. The pattern is specific: appetite ratings before the meal were higher, while fullness afterwards was the same. So it pushes you to start eating rather than leaving you unsatisfied after. GHRP-2 acts on the same receptor as ghrelin, which is why.
Is GHRP-2 the same as HGH?
No, they work very differently. HGH (somatropin) is the actual growth hormone that you inject directly into your body. GHRP-2 stimulates your own pituitary gland to produce and release more of YOUR natural growth hormone. GHRP-2 creates more physiological, pulsatile GH release patterns, while HGH injections provide constant elevated levels.
What time of day should I take GHRP-2?
The approved label gives one timing instruction: fasted [6]. Beyond that, no human trial of GHRP-2 has compared times of day, so the before-bed and on-waking recommendations are reasoning from the body's own overnight GH pulse rather than a measured result. The chronic study that did dose at night found each injection's effect was brief, with little influence on GH secretion later in the night [5]. The three-times-daily schedule this page used to publish — morning, post-workout, bedtime — appears in no trial and on no label.
How long can I use GHRP-2?
There is no evidence-based answer, and the 8-12 weeks on / 4-8 weeks off pattern that circulates comes from community practice rather than any trial or label. The approved use is a single injection [6]. The longest anyone has been dosed in a published study is 8 months — 6 growth-hormone-deficient children, escalating from 0.3 to 3.0 mcg/kg/day, with no side effects observed in that small group but also no rise in IGF-I [5]. Nobody has studied repeated GHRP-2 in healthy adults at all, so claims about maintaining pituitary sensitivity through cycling are not built on data.
Further reading
GHRP-2 history & related research
Ready for the protocol?
Every dosing tier, administration route, timing note, and dose-adjustment rule for GHRP-2, on one page.