GHRP-2 vs Ipamorelin
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].
A uniquely selective growth hormone booster that tells your pituitary to release more GH without messing with your cortisol or other hormones—making it the 'clean' choice among growth hormone peptides.
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Quick comparison
Dose range
GHRP-2
100–100 mcg
Ipamorelin
200–200 mcg
Frequency
GHRP-2
Single dose (approved diagnostic use)
Ipamorelin
Multiple times daily
Administration
GHRP-2
Intravenous (approved diagnostic use)
Ipamorelin
Subcutaneous injection
Cycle length
GHRP-2
Not established — the approved use is one injection
Ipamorelin
8-12 weeks
Onset speed
GHRP-2
Rapid (hours to days)
Ipamorelin
Moderate (1-2 weeks)
Evidence level
GHRP-2
Approved diagnostic agent in Japan; no treatment approval anywhere
Ipamorelin
Moderate human trials (Phase 1-2)
Benefit ratings
GH Release
Recovery Speed
Sleep Quality
GH Selectivity
Recovery Support
Safety Profile
Compound specifications
GHRP-2
Molecular formula
C45H55N9O6
Molecular weight
817.97 g/mol
Half-life
15-60 minutes
Bioavailability
High (subcutaneous)
CAS number
158861-67-7
Ipamorelin
Molecular formula
C38H49N9O5
Molecular weight
711.85 g/mol
Half-life
2 hours
Bioavailability
High when injected subcutaneously
CAS number
170851-70-4
Dosing compared
GHRP-2
Intravenous
100 mcg
Single dose, once — this is a diagnostic test · One administration
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 releases [6]. It is a one-off test. Nothing about this approval extends to repeated dosing or to injecting under the skin.
Subcutaneous
0.3 – 3 mcg/kg/day
Once daily · 2 months per dose level, 8 months in total
The only chronic subcutaneous 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.
100 – 300 mcg per dose
1-3 times daily (community practice) · Undefined — no trial has run this schedule
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 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].
Ipamorelin
Subcutaneous
100 mcg per injection
2-3 times daily · 4-8 weeks
Conservative entry dose; Ipamorelin is a selective GH secretagogue with a ~2 hour half-life, so doses are split through the day [1][2]. Used in research and practice to assess tolerance before titrating up.
200 mcg per injection
2-3 times daily · 8-12 weeks
Most commonly cited research/practice dose; gives a meaningful pulsatile GH release without raising cortisol or prolactin at standard doses [1][2].
300 mcg per injection
3 times daily · 8-12 weeks
Upper end of the commonly used range; total daily exposure split across three injections. Used in practice by experienced users [1].
Best suited for
GHRP-2
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.
Ipamorelin
Clean GH Boost Seekers
If you want the benefits of increased growth hormone without spiking cortisol or other stress hormones, Ipamorelin is uniquely selective. Unlike GHRP-2 or GHRP-6, it won't raise your cortisol levels even at doses 200 times higher than needed for GH release.
Recovery-Focused Athletes
Ipamorelin shines for athletes who want better recovery between training sessions. The GH boost helps repair muscle tissue faster, and since it doesn't mess with other hormones, you can use it consistently without the rollercoaster effects.
Anti-Aging Enthusiasts
Growth hormone naturally declines as we age, contributing to muscle loss, fat gain, and reduced vitality. Ipamorelin offers a gentle way to restore more youthful GH levels without the risks of actual HGH therapy.
Those Recovering from Steroid Use
Research shows Ipamorelin can help counteract the muscle and bone-weakening effects of glucocorticoid medications. If you've been on steroids for medical reasons, this peptide may help you rebuild what you've lost.
Side effects
GHRP-2
Common
- Substantially increased food intake
- Gastrointestinal effects
- Feeling of warmth, drowsiness, runny nose
Uncommon
- Low blood pressure
- Raised white cell count and lactate
Ipamorelin
Common
- Mild headache
- Injection site reactions
- Water retention
- Increased appetite
Uncommon
- Tingling in hands or feet
- Joint stiffness
Serious
- Allergic reaction
Safety & evidence
GHRP-2
Evidence level
Approved diagnostic agent in Japan; no treatment approval anywhere
FDA 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.
Safety overview
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].
Contraindications
- Pregnancy or breastfeeding — no human data
- Known hypersensitivity to pralmorelin
- Anyone for whom a 33% rise in food intake is the opposite of the goal — that is the measured effect at 1 mcg/kg/hour [7]
- There is no treatment label anywhere, so there is no authoritative contraindication list for repeated use
Ipamorelin
Evidence level
Moderate human trials (Phase 1-2)
FDA status
Research compound
Safety overview
Ipamorelin's main selling point is that it raises growth hormone without raising cortisol or ACTH — two stress hormones that similar peptides do raise. That was shown in pigs, and it held even at doses more than 200 times higher than the amount needed to raise growth hormone [1]. It has not been checked in people. The two published human studies measured ipamorelin and growth hormone only; neither one assayed cortisol, ACTH or prolactin [2][3]. Most of what we know about safety in people comes from a single trial in patients recovering from bowel surgery. 114 people took part: 56 got ipamorelin through an IV for up to seven days, and 58 got a placebo. Most side effects were mild to moderate, and were the kind you would expect after surgery [3]. Serious problems happened at about the same rate in both groups — roughly 1 in 6 either way (17.9% on ipamorelin, 15.5% on placebo). But three things were more common on ipamorelin: low potassium in about 1 in 8 people versus about 1 in 30 on placebo (12.5% vs 3.4%), trouble sleeping in about 1 in 9 versus about 1 in 19 (10.7% vs 5.2%), and high blood sugar at discharge in about 1 in 7 versus about 1 in 12 (14.3% vs 8.6%) [6]. Two people taking ipamorelin died. Both had colon cancer surgery, and in both cases the surgical join in the bowel leaked afterward. Nobody on the placebo died. The FDA says it is unclear whether those deaths had anything to do with ipamorelin — but it pointed to them, along with the potassium and blood sugar differences, when it recommended in October 2024 against letting pharmacies compound ipamorelin [6].
Contraindications
- Active cancer or history of cancer
- Pregnancy or breastfeeding
- Pituitary disorders or tumors
- Known allergy to peptide components
- Children and adolescents (growth plates still open)
Which is right for you?
Choose GHRP-2 if...
- Growth hormone optimization
- Muscle building
- Recovery enhancement
- Anti-aging
Choose Ipamorelin if...
- Muscle recovery and growth
- Anti-aging and vitality
- Body composition improvement
- Sleep quality enhancement