Growth hormone
A peptide that triggers a pulse of growth hormone. Approved in Japan — but only as a one-time diagnostic test for growth hormone deficiency, not as a treatment.
Start here
GHRP-2 is a lab-made peptide that copies the hormone ghrelin (the hunger hormone) to trigger a pulse of growth hormone from the pituitary (the master hormone gland at the base of the brain) gland. Its only approval anywhere is in Japan, as a single-dose test for diagnosing growth hormone deficiency — not as a treatment 6. It is not FDA-approved, and the one long-term human study, 8 months in 6 children, raised growth hormone but left IGF-I unchanged 5.
Your pituitary (the master hormone gland at the base of the brain) 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.
GHRP-2 (Growth Hormone Releasing Peptide-2) is a lab-made chain of six amino acids that strongly triggers growth hormone (GH) release. It switches on the growth hormone secretagogue (a compound that prompts your body to release growth hormone) receptor (GHS-R1a), the same docking site that ghrelin, the body's own hunger hormone, uses. After it attaches, it makes pituitary (the master hormone gland at the base of the brain) somatotroph cells (GH-making cells) release their stored GH in pulses. GHRH (the brain's natural GH signal) uses a different receptor. GHRP-2 boosts GH release by a complementary route, which explains why combining the two types has a synergistic effect (a combined effect bigger than the sum of the parts), a 5-10x amplification. GHRP-2 also makes the hypothalamus (the brain region that runs your hormone system) release more GHRH and lowers somatostatin (the hormone that switches growth hormone release off) tone (the brake that holds GH back), which raises GH output further. It also triggers ACTH release from corticotroph cells (a stress hormone signal), causing a brief rise in cortisol (the stress hormone). The half-life (how long it stays active in your body) in blood is 15-60 minutes, but its effects on GH pulses last longer. Downstream, it raises IGF-1 (a growth signal set off by GH) production in the liver and other tissues, which carries many of the muscle-building and repair benefits linked to GH.
Evidence check
Approved diagnostic agent in Japan; no treatment approval anywhere
We couldn't classify the research behind this one — read the full profile before forming an opinion.
Every numbered marker on this page links to one of the 8 sources at the bottom.
Growth Hormone Release
This part is real and well documented. GHRP-2 switches on the growth hormone-releasing receptor and produces a reliable GH pulse, reliably enough that Japan approves a single 100 μg dose into a vein as a diagnostic test, with a peak below 15 μg/L taken as evidence of deficiency. The pulse is brief: in 8 months of daily dosing, each injection's effect faded with little carry-over later in the night.
Recovery Speed
Not demonstrated, and the usual justification does not hold. Recovery claims run through IGF-1 (the growth signal GH triggers), but in the only long-term human study, 6 children dosed for 8 months, blood levels of IGF-I and its carrier protein IGFBP-3 did not rise at any dose. 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.
The most-asked question
The research-reported range is 100 mcg, single dose (approved diagnostic use). Studies used different doses for different situations — find yours:
Diagnosing growth hormone deficiency (the approved use)
100 mcg
The only dose of GHRP-2 approved by any regulator. Japan approves pralmorelin hydrochloride as GHRP Kaken 100 for diagnosing growth hormone deficiency: dissolve the vial in 10 mL of saline immediately before use and inject 100 μg slowly into a vein, fasted, for anyone 18 or over. Children aged 4 to under 18 get 2 μg/kg, capped at 100 μg above 50 kg. Blood is then sampled to see how much growth hormone the pituitary (the master hormone gland at the base of the brain) releases 6. It is a one-off test. Nothing about this approval extends to repeated dosing or to injecting under the skin.
The only published repeated-dose regimen
0.3 – 3 mcg/kg/day
The only chronic subcutaneous (under the skin) dosing ever published, and it was in 6 growth-hormone-deficient children, not adults: 0.3, then 1.0, then 3.0 mcg/kg per day, each for 2 months 5. Overnight GH rose with dose and growth velocity improved, but serum IGF-I and IGFBP-3 did not increase at any dose, and each injection's effect was brief. For a 75 kg adult these levels would be about 22 to 225 mcg a day — which is where the commonly quoted per-dose figures roughly land, though no trial has given them to an adult on that schedule.
Community practice — listed because it is used, not because it is evidenced
100 – 300 mcg per dose
Community-reported, not peer-reviewed and not on any label. This is the schedule most people asking about GHRP-2 mean, and it is worth being plain about what stands behind it: no human trial has dosed an adult subcutaneously (under the skin) one to three times daily at these amounts. The previous version of this page attributed the range to a study that does not contain it. What IS known at comparable exposures is that GHRP-2 raises food intake substantially — 33.5% above placebo at 1 mcg/kg/hour in 19 adults 7 — and that in the one chronic study IGF-I did not move 5.
The ceiling: 300 mcg three times daily (900 mcg total daily)
Reconstitution, in plain words
Peptides usually arrive as a freeze-dried powder in a small vial. “Reconstitution” just means adding sterile water back in so you can measure a dose. Here's how it works for GHRP-2:
5mg vial + 2.5mL BAC water = 2mg/mL (2000mcg/mL). For 200mcg dose, draw 0.1mL (10 units on insulin syringe).
At 2000mcg/mL concentration: 0.05mL (5 units) = 100mcg, 0.1mL (10 units) = 200mcg, 0.15mL (15 units) = 300mcg
Three quick questions — your vial, your water, your dose — and it tells you the exact syringe mark. “Find dose amount” is preloaded with GHRP-2's recorded schedule.
Injection sites & technique
Subcutaneous (under the skin) injection into fatty tissue
Timing
Morning upon waking, post-workout, and before bed (on empty stomach)
Must be taken on an empty stomach—wait at least 30-60 minutes before eating. Food significantly blunts the GH release response.
For maximum effect, combine with a GHRH peptide like CJC-1295 or Sermorelin at the same time. The synergy between GHRP and GHRH can amplify GH release by 5-10x compared to either alone.
The honest list
These show up most often. They usually fade as your body adjusts.
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.
What to do 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.
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.
What to do Reported after a single dose; no management is specified on the label.
All three are listed adverse reactions on the Japanese label 6.
What to do Transient on the label's account.
Worth knowing about, but most people never see these.
Hypotension is a listed adverse reaction on the Japanese diagnostic label 6.
What to do The label's dose is given fasted with the patient in a clinical setting. Sitting or lying down is sensible if it occurs.
Leukocytosis is on the Japanese label 6. In critically ill men, 5 days of GHRP-2 infused alone at 1 mcg/kg/hour raised both serum lactate and white cell count by day 5, where the fuller hormonal replacement in the same trial did not 8.
What to do Both are laboratory findings a prescriber can track; neither is self-detectable.
Week by week
Is it right for you?
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.
GH has anti-insulin effects (it makes the body respond less to insulin). May need insulin dose changes. Monitor closely.
May affect blood sugar control. Monitor glucose levels carefully.
Both affect cortisol (the stress hormone) and the HPA axis (the body's stress hormone system). Use with caution and medical supervision.
GH can affect how thyroid hormone is converted. Monitor thyroid levels.
Excellent synergy: combining a GHRP with a GHRH (the brain's GH-releasing signal) amplifies GH release 5-10x. Can inject together.
Both are GHRPs (GH-releasing peptides). Using together is redundant and may cause excessive appetite stimulation.
Both are GHRPs. Do not stack together. Choose one based on appetite preference.
Good synergy as a GHRH analog (a drug that copies the brain's GH-releasing signal). Can be combined for more GH release.
Safe to combine for recovery benefits. Different mechanisms, no interactions.
May enhance GH release when taken together. Safe combination.
May support GH release. Safe to combine.
Both taken before bed. May have additive sleep benefits.
Essential for muscle building goals. Take protein 30+ minutes after peptide injection.
GHRP-2 excels at stimulating your pituitary (the master hormone gland at the base of the brain) 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.
Athletes and fitness enthusiasts love GHRP-2 for its ability to speed up recovery between workouts. The elevated GH and IGF-1 (a growth signal your liver releases in response to growth hormone) levels help repair muscle tissue faster, reduce soreness, and support lean muscle growth—especially when combined with proper training and nutrition.
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.
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.
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.
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 these adverse reactions: stomach rumbling, raised white blood cell count, a feeling of warmth, low blood pressure, nausea, stomach discomfort, bloating, drowsiness and runny nose. But that label covers a single 100 μg dose into a vein, not repeated use 6. In 6 children with growth hormone deficiency given 0.3 to 3.0 mcg/kg/day for 8 months, no side effects or toxicities were observed, in a group far too small to detect anything uncommon 5. One warning sign from longer infusion: in critically ill men, GHRP-2 given alone at 1 mcg/kg/hour for 5 days raised blood lactate (a marker of the body under strain) and white blood cell count by day 5, which the fuller hormone replacement in the same trial did not 8.
GHRP-2 has one regulatory approval in the world, in Japan, for a single dose into a vein 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 research is mostly short studies of how the body's hormone gland responds: single doses and short infusions in small groups of volunteers, largely from Bowers and Veldhuis. The only long-term dosing evidence is one study in 6 children over 8 months, where IGF-I (the growth signal GH triggers) 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.
Keeping it good
Store lyophilized (freeze-dried) powder refrigerated at 36-46°F (2-8°C) for several months. Can also be stored frozen at -4°F (-20°C) for longer-term storage up to 24 months. Keep in original packaging away from direct light.
Refrigerate immediately at 36-46°F (2-8°C). Never freeze after reconstitution—this destroys the peptide. Store away from light. Discard after 28 days or if any degradation signs appear.
Not our opinion — the published record
2013
Testosterone and estradiol (sex hormones) help determine how strongly older men respond to GHRP-2 with GH, while BMI (body mass index) lowers GH pulses during a GHRP-2 infusion (slow drip).
Norman C et al.
2009
GHRP-2 was a stronger GH trigger than GHRH in women. Age and estrogen status together explained 60% of the differences in how well GHRP-2 worked.
Veldhuis JD et al.
2009
L-arginine combined with GHRP-2 gives a strong GH stimulus that stays effective even during short-term hormone deficiency, and is not affected by visceral (belly) fat or IGF-1 levels.
Veldhuis JD et al.
2009
Abdominal visceral fat (fat around the organs) is the strongest negative predictor of how well both GHRH and GHRP-2 work. Fasting IGF-I concentration goes up with how well these secretagogues (GH-triggering drugs) work.
Veldhuis JD et al.
1998
The only long-term human study of GHRP-2, and it is small. Six prepubertal children with growth hormone deficiency received increasing doses under the skin of 0.3, then 1.0, then 3.0 mcg/kg per day, each for a 2-month period, followed by a fourth period combining 3 mcg/kg GHRP-2 with 3 mcg/kg GHRH. Overnight GH release rose with the dose and growth velocity (growth rate) was higher during treatment than before or after. But serum IGF-I and IGFBP-3 (blood markers that GH normally raises) DID NOT INCREASE, and the GH profiles showed that each injection's effect was brief, with little influence on release later in the night. No side effects or toxicities were seen in those 6 children. The authors' own conclusion is that products that act for longer would be needed for GHRP-2 to be useful as a treatment.
Mericq V, Cassorla F, Salazar T, Avila A, Iniguez G, Bowers CY, Merriam GR
2025
The only regulatory approval this compound has anywhere, and it is for a diagnostic test rather than a treatment. The approved use is diagnosing growth hormone deficiency (成長ホルモン分泌不全症の診断). The dose is a SINGLE slow injection into a vein, given fasted, after dissolving the vial in 10 mL of saline: 100 μg for anyone aged 18 or over, and 2 μg per kg of body weight for ages 4 to under 18, capped at 100 μg for children over 50 kg. Adverse reactions listed on the label are abdominal rumbling, leukocytosis (high white blood cell count), a feeling of warmth, low blood pressure, nausea, stomach discomfort, abdominal swelling (distension), drowsiness and a runny nose. Nothing on this label covers repeated dosing, injection under the skin, or use for body composition.
Kaken Pharmaceutical Co., Ltd.; Pharmaceuticals and Medical Devices Agency (PMDA), Japan
2006
The clearest measurement of what GHRP-2 does to appetite in people. Nineteen healthy adults with stable weight (10 lean, 9 obese) each received, double-blind (neither they nor the researchers knew which) and in random order, a slow drip under the skin of GHRP-2 at 1 mcg/kg/hour, 0.1 mcg/kg/hour, or placebo over 270 minutes, then ate freely at a buffet lunch. Food intake rose 10.2 ± 3.9% at the low rate (p=0.011) and 33.5 ± 5.8% at the high rate (p<0.001) compared with placebo, rising with the dose. Obesity did not blunt the effect: obese participants responded as much as lean ones, in both food intake and GH. Appetite ratings before the meal were higher while fullness afterwards was the same, so the drive is to start eating rather than to stop later.
Laferrère B, Hart AB, Bowers CY
2002
Thirty-three critically ill men were randomly assigned to 5 days of placebo (n=7), GHRP-2 alone at 1 mcg/kg/hour (n=9), GHRP-2 plus TRH (n=9; TRH is a brain hormone that signals the thyroid), or GHRP-2 plus TRH plus pulsatile GnRH (n=8; GnRH given in pulses). GHRP-2 alone restarted GH release and brought IGF-I, IGFBP-3 and the acid-labile subunit (blood proteins that carry and stabilize IGF-I) back to normal. It did not deliver the metabolic benefit: ureagenesis (the body's breakdown of protein into urea) fell with the two combinations (p=0.01 and p=0.009) but NOT with GHRP-2 alone, and osteocalcin (a bone-building marker) rose only with the triple combination. By day 5, blood lactate and white cell count were higher with GHRP-2 alone and with GHRP-2 plus TRH, but not with the triple combination. Restoring one hormone system in isolation was not enough, and carried signals the fuller replacement did not.
Van den Berghe G, Baxter RC, Weekers F, et al.
If this isn't the right fit
Your questions
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 (the stress hormone) and prolactin (a hormone tied to lactation and libido) 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.
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.
Yes, but strategically! GHRP-2 works best when combined with a GHRH peptide (a peptide that mimics the body's own growth hormone-releasing signal) 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.
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.
It will make you eat more, and this has been measured rather than guessed. In 19 adults given a drip under the skin, double-blind against placebo (neither they nor the researchers knew who got which), the amount they chose to eat rose 10.2% at 0.1 mcg/kg/hour and 33.5% at 1 mcg/kg/hour. The effect grew with dose and was just as strong in obese participants as lean ones 7. The pattern is specific: hunger ratings before the meal were higher, while fullness afterwards was the same. So it pushes you to start eating rather than leaving you unsatisfied afterwards. GHRP-2 acts on the same receptor as ghrelin (the hunger hormone), which is why.
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 (the master hormone gland at the base of the brain) 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.
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.
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 (the master hormone gland at the base of the brain) sensitivity through cycling are not built on data.
8 sources
Every numbered marker on this page points to one of these. Same sources, same numbering as the GHRP-2 research profile on Peptide Initiative.
Want the deep science?
Every claim on this page traces back to the research database behind Peptide Initiative — studies, citations, clinical trial data, and the technical detail we deliberately left out here.
Open the research profileThis guide is education, not medical advice. GHRP-2 is a research compound that is not FDA-approved for human use. Talk to a clinician before taking anything.
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