Ipamorelin vs Pralmorelin (GHRP-2)
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.
A powerful hexapeptide that stimulates growth hormone release—used clinically in Japan for GH testing and studied for healing and anti-inflammatory effects.
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Quick comparison
Dose range
Ipamorelin
200–200 mcg
Pralmorelin (GHRP-2)
1–1 mcg/kg/hour
Frequency
Ipamorelin
Multiple times daily
Pralmorelin (GHRP-2)
Once daily
Administration
Ipamorelin
Subcutaneous injection
Pralmorelin (GHRP-2)
Subcutaneous injection
Cycle length
Ipamorelin
8-12 weeks
Pralmorelin (GHRP-2)
4-6 weeks
Onset speed
Ipamorelin
Moderate (1-2 weeks)
Pralmorelin (GHRP-2)
Rapid (hours to days)
Evidence level
Ipamorelin
Moderate human trials (Phase 1-2)
Pralmorelin (GHRP-2)
Limited human trials
Benefit ratings
GH Selectivity
Recovery Support
Safety Profile
Muscle & Performance Enhancement
Injury Recovery & Healing
Diagnostic Clinical Use
Compound specifications
Ipamorelin
Molecular formula
C38H49N9O5
Molecular weight
711.85 g/mol
Half-life
2 hours
Bioavailability
High when injected subcutaneously
CAS number
170851-70-4
Pralmorelin (GHRP-2)
Molecular formula
C45H55N9O6
Molecular weight
818.0 g/mol
Half-life
15-60 minutes
Bioavailability
~100% (subcutaneous injection)
CAS number
158861-67-7
Dosing compared
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].
Pralmorelin (GHRP-2)
Subcutaneous
1 mcg/kg/hour (continuous infusion) in research settings
Continuous infusion · Study-defined (e.g. ~270 minutes in published trials)
Subcutaneous infusion dose used in controlled human GH-release/appetite studies; not an approved therapeutic regimen. [4]
Intravenous
100 mcg (0.1 mg) single bolus (diagnostic GH-stimulation test)
Single administration · Single test; blood sampled at 0, 15, 30, 60 min
Japan-approved diagnostic dose (GHRP Kaken 100) for growth hormone deficiency; fixed 100 mcg IV bolus. A research GH-stimulation dose of 1 mcg/kg IV is also documented. [1]
Best suited for
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.
Pralmorelin (GHRP-2)
Athletes and Fitness Enthusiasts
If you're serious about lean muscle gains and recovery, pralmorelin directly stimulates GH release—one of the body's most powerful anabolic hormones. [7][9] Most athletes in research settings use 100-200 mcg for faster muscle repair and improved performance.
Individuals Recovering from Injury
Recent animal studies show GHRP-2 reduces inflammation and speeds tendon-bone healing. [3] If you're dealing with sports injuries, rotator cuff issues, or fractures, this peptide's anti-inflammatory profile may accelerate recovery when combined with proper rehab.
Those Seeking Diagnostic GH Testing
If your doctor suspects growth hormone deficiency, pralmorelin is the gold-standard diagnostic tool in Japan and many countries. A single injection stimulates GH release, allowing physicians to assess your pituitary function safely and accurately [1][5][6].
Peptide Research Enthusiasts
Pralmorelin is one of the most extensively studied GHRPs worldwide. If you're exploring peptide protocols and understand research-grade products, this is a powerful tool for understanding how your GH axis responds to stimulation.
Side effects
Ipamorelin
Common
- Mild headache
- Injection site reactions
- Water retention
- Increased appetite
Uncommon
- Tingling in hands or feet
- Joint stiffness
Serious
- Allergic reaction
Pralmorelin (GHRP-2)
Common
- Facial flushing
- Transient headache
- Increased appetite
- Temporary dizziness or lightheadedness
Uncommon
- Carpal tunnel-like sensations
- Joint or muscle aches
- Sleep quality changes
Serious
- Severe allergic reaction (anaphylaxis)
Safety & evidence
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)
Pralmorelin (GHRP-2)
Evidence level
Limited human trials
FDA status
Research compound
Safety overview
Pralmorelin (GHRP-2) has been safely used in diagnostic settings in Japan for decades and is well-tolerated in most individuals when used at appropriate doses. [5][6][11] The peptide is synthetic and chemically stable, with low immunogenicity risk. However, it is NOT FDA approved and should only be used under medical supervision or within research protocols. Long-term safety data in healthy humans is limited.
Contraindications
- Active malignancy or unresolved cancer history
- Uncontrolled hypertension or severe cardiovascular disease
- Pregnancy or breastfeeding
- Acute infection or sepsis
- Uncontrolled diabetes
Which is right for you?
Choose Ipamorelin if...
- Muscle recovery and growth
- Anti-aging and vitality
- Body composition improvement
- Sleep quality enhancement
Choose Pralmorelin (GHRP-2) if...
- Athletes seeking enhanced recovery and lean mass gains
- Individuals with suspected GH deficiency (diagnostic use)
- Recovery from tendon or bone injuries
- Those wanting to test GH axis responsiveness