Overview
Ipamorelin is a synthetic pentapeptide that acts at the ghrelin receptor (GHS-R1a) to stimulate pituitary growth hormone release. It was developed in the 1990s as a more selective GHRP than GHRP-2 or GHRP-6, with much less cortisol and prolactin elevation in early animal and short human studies. It was investigated for postoperative ileus before development was discontinued, so the published human dose-finding evidence is shallower than its popularity in self-experimenter communities suggests.
Mechanism
Selective agonism of the GHS-R1a (ghrelin receptor) on pituitary somatotrophs and the arcuate nucleus, triggering pulsatile endogenous GH release. Selectivity for GH over ACTH, prolactin, and FSH/LH distinguishes it from older GHRPs.
Evidence by indication
We classify each indication separately. The same peptide can be Tier 1 for one use and Tier 4 for another. Tiers reflect the published literature, not the strength of community framing.
Stimulation of GH release in healthy adults
Small human studies (Raun et al. and follow-ups) demonstrated selective GH release with minimal effect on cortisol or prolactin. These are short-duration pharmacology studies, not outcome trials.
Postoperative ileus
A Phase 2b RCT in postoperative ileus showed mixed results and development was halted. Worth knowing: the only large-scale human RCT for ipamorelin is in this discontinued indication, not the body-composition claims it is sold against today.
Body composition / muscle gain
No published human RCTs evaluate ipamorelin (alone or stacked) for hypertrophy, body fat reduction, or athletic performance. Claims rest on extrapolation from GH/IGF-1 elevation rather than direct measurement of body-composition outcomes.
No primary citations are anchored to this indication — the tier reflects the absence of usable literature, not a missing reference.
Sleep quality
GH pulses occur predominantly during slow-wave sleep, and GHRP/GHRH pairings can amplify these. There are no controlled human trials specifically of ipamorelin and sleep architecture, however.
No primary citations are anchored to this indication — the tier reflects the absence of usable literature, not a missing reference.
Studied dose ranges
The ranges below come from published trial protocols where available, and from documented self-experimenter consensus where the literature does not include human dose-finding work. The notes flag which is which.
Most published human dose ranges fall between 100–300 mcg per injection, often paired with a GHRH analog (e.g., CJC-1295 or sermorelin). Higher doses do not produce proportionally larger GH pulses.
Contraindications
- Active malignancy (relative — GH/IGF-1 is theoretically permissive of tumor growth)
- Pregnancy and breastfeeding
- Severe insulin resistance or uncontrolled diabetes (GH is counter-regulatory to insulin)
- Pituitary or hypothalamic disease — confirm with provider before use
- Hypersensitivity to ipamorelin
Reported side effects
- Injection site reactions
- Transient hunger increase (ghrelin-receptor effect)
- Headache
- Fluid retention with chronic use
- Mild fatigue or drowsiness shortly after dosing
- Possible insulin sensitivity decrease at higher cumulative doses
Reconstitution & storage
Most ipamorelin sold for research is a lyophilized powder reconstituted with bacteriostatic water (BAC). Aim for a concentration that yields ergonomic doses on a U-100 syringe — 5 mg in 2 mL gives 2.5 mg/mL, putting a 200 mcg dose at 8 units. Use the calculator to verify.
Storage. Lyophilized vial: room temperature is acceptable short-term; refrigeration (2–8 °C) extends stability. Reconstituted: refrigerate 2–8 °C, use within 30 days. Avoid repeated temperature cycling.
Open the peptide calculator → to compute exact draw volumes for your specific vial and BAC water choice.
Editorial note
Ipamorelin's reputation outpaces its evidence. The selective-GH-release pharmacology is real and replicated; the clinical-outcome story is not. Resist tier inflation.
Citations
- [1]Ipamorelin, the first selective growth hormone secretagogueRaun K, Hansen BS, Johansen NL, et al. · European Journal of Endocrinology · 1998 · PMID 9789012Original characterization of ipamorelin's GH selectivity.View source
- [2]Effect of ipamorelin, a novel selective growth hormone secretagogue, on the recovery of GI function in postoperative ileusBeck DE, Sweeney WB, McCarter MD, et al. · International Journal of Colorectal Disease · 2014 · PMID 24309627Phase 2b RCT in postoperative ileus — the largest human dataset for ipamorelin.View source