Peptide Reference · Growth Hormone
Ipamorelin
Ipamorelin is a selective growth hormone secretagogue, a synthetic pentapeptide that prompts the pituitary to release the body’s own growth hormone with minimal effect on cortisol, prolactin, or appetite.
For research and educational purposes only · Not for human consumption
In Brief
Ipamorelin is one of the cleanest growth hormone secretagogues. It mimics the hunger hormone ghrelin at a specific pituitary receptor to trigger natural pulses of growth hormone, but unlike older peptides in its class it does this without meaningfully raising cortisol or prolactin, and without driving hunger.
It was developed by Novo Nordisk in the late 1990s and tested in humans for post-surgery gut recovery, but it was never approved for any use. It is most often paired with a GHRH peptide such as CJC-1295. Evidence in humans is limited, and it remains a research compound that is banned in competitive sport.
Overview
Ipamorelin is a synthetic pentapeptide and a growth hormone secretagogue, meaning it stimulates the body to release its own growth hormone rather than supplying growth hormone directly. It was developed by Novo Nordisk in the late 1990s under the code NNC 26-0161 and is considered a third-generation growth-hormone-releasing peptide (GHRP).
Its defining trait is selectivity. Ipamorelin binds the ghrelin receptor (the growth hormone secretagogue receptor, GHS-R1a) in the pituitary and triggers a clean pulse of growth hormone, with minimal effect on cortisol, prolactin, or ACTH, and without the strong hunger that older GHRPs such as GHRP-6 produce. In research and athletic contexts it is frequently combined with a GHRH analogue such as CJC-1295, since the two act through complementary pathways. It was investigated in human phase II trials for postoperative ileus but discontinued for lack of efficacy, and it is not approved for human use anywhere.
Common research uses
Ipamorelin has been studied or applied in the following contexts. None of these is an approved therapeutic indication.
- Growth hormone stimulation: triggering pulsatile release of endogenous growth hormone through the ghrelin receptor.
- Body composition and recovery: used informally, often stacked with CJC-1295, in the hope of supporting lean mass and recovery.
- Bone: increased bone growth and mineral content in animal models.
- Gastrointestinal motility: evaluated in human phase II trials for postoperative ileus after bowel surgery.
- Sleep: growth hormone pulses occur largely during deep sleep, and pre-bed dosing is common, though sleep benefits are anecdotal.
- Selectivity research: a reference compound for studying GH release without the cortisol and prolactin rise seen with other GHRPs.
Outside the laboratory, ipamorelin is used informally for recovery and body-composition goals. This use is unapproved, unregulated, and prohibited under WADA anti-doping rules.
Mechanism of action
Ipamorelin is a selective agonist of the ghrelin receptor and works upstream of growth hormone release:
- Selective GHS-R1a agonism: mimics ghrelin at the growth hormone secretagogue receptor in the anterior pituitary, prompting growth hormone release.
- Pulsatile release: produces growth hormone in natural pulses rather than a sustained flood, which more closely resembles normal physiology.
- Somatostatin suppression: reduces the inhibitory signal that normally brakes growth hormone output.
- Hormone selectivity: at typical doses it does not meaningfully raise cortisol, prolactin, ACTH, or aldosterone, which distinguishes it from GHRP-6 and GHRP-2.
- No appetite or lipogenic effect: unlike ghrelin itself and some other GHRPs, it does not strongly stimulate hunger.
Because it acts on a different receptor than GHRH analogues, ipamorelin is often paired with one (such as CJC-1295) to produce a larger, synergistic growth hormone pulse than either alone.
Protocols
Quick Reference
Syringe units assume a 5 mg vial reconstituted with 2 mL BAC water (2.5 mg/mL) drawn in a 1 mL / 100-unit insulin syringe.
Dosing protocols
Published sources differ on dosing. Compare all three below, each labelled by evidence tier. None is an approved human protocol.
| Protocol | ResearchPreclinical literature ↗ | ClinicalDr. W. Seeds, Peptide Protocols ↗ | CommunityPeptides For Men (N. Wells) ↗ |
|---|---|---|---|
| Recommended dose | 0.2 mg | 0.1 mg | 0.3 mg |
| Units (1 mL syringe) | 8 | 4 | 12 |
| Timing | Before bed | Before bed | AM & PM |
| Frequency | Once daily | Once daily | 1–2× daily |
| Duration | 12 weeks | 12 weeks (often with a GHRH) | 8–12 wk on, equal rest |
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Administration Routes
Ipamorelin is given by subcutaneous injection. Timing and stacking matter more than route, because growth hormone release is blunted by food and amplified by a GHRH partner.
Subcutaneous (SC)
Injection into the fat layer under the skin, usually the abdomen, with a short insulin needle. The standard route for ipamorelin and easy to self-administer.
Timing & fasting
Carbohydrate and fat blunt the growth hormone response, so doses are typically taken on a relatively empty stomach, commonly before bed to align with the body’s natural overnight GH pulse.
Stacking
Ipamorelin acts on the ghrelin receptor while GHRH analogues act on a separate receptor, so the two are commonly combined for a larger, synergistic growth hormone pulse.
Reconstitution Guide
Ipamorelin is supplied as a lyophilised powder and must be reconstituted before use. New to this? See Peptides 101 for the fundamentals.
Gather supplies
Bacteriostatic water (BAC water), alcohol swabs, a 1 mL insulin syringe, and the peptide vial. BAC water contains 0.9% benzyl alcohol which prevents bacterial growth across multiple uses.
Calculate your dilution
A common dilution for a 5 mg vial: add 2 mL BAC water for a concentration of 2.5 mg/mL. At that strength a 0.2 mg dose is roughly 8 units on a U-100 syringe. Use the calculator below for your own numbers.
Add the water slowly
Wipe both vial tops with an alcohol swab. Draw the BAC water into the syringe. Insert the needle and angle it so the stream runs down the inside wall of the vial, not directly onto the powder cake.
Mix gently
Once all water is added, swirl gently in a circular motion until the powder is fully dissolved. Do not shake or vortex; agitation can degrade the peptide structure.
Store correctly
Reconstituted peptide: refrigerate at 2–8°C, away from light. Use within 4 weeks. Lyophilised powder: store frozen at −20°C for long-term. Label with the reconstitution date.
Reconstitution Calculator
Enter your vial size, water volume, and intended dose to calculate the exact volume and syringe markings.
⚠ This calculator is a reference tool only. Verify all calculations independently before use.
Active compound & chemistry
Ipamorelin is a synthetic pentapeptide with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2. Its molecular formula is C₃₈H₄₉N₉O₅ and its molecular weight is approximately 711.9 Da (CAS 170851-70-4). The non-standard residues, including alpha-aminoisobutyric acid (Aib) and several D-amino acids, make it resistant to enzymatic breakdown and give it a circulating half-life of roughly two hours.
It is a selective agonist of the growth hormone secretagogue receptor (GHS-R1a), the same receptor targeted by the natural hormone ghrelin. Look up the compound in PubChem for full structural data, canonical SMILES, and InChI.
Evidence summary
The evidence base for ipamorelin is moderate: solid pharmacology characterising how it works, strong animal data, and a small amount of human trial data that did not lead to approval.
Selective growth hormone release
The original characterisation showed that ipamorelin releases growth hormone with a potency comparable to older GHRPs, but without the rise in ACTH and cortisol they cause. This selectivity is the central reason it became the preferred research GHRP.
Raun K et al. (1998) · Eur J Endocrinol · View on PubMed →
Postoperative ileus phase II trial
Ipamorelin was advanced into human phase II trials for postoperative ileus, the slowing of gut function after bowel surgery, on the rationale that ghrelin-receptor agonism promotes motility. The program was discontinued after the trials did not show sufficient efficacy.
Phase II clinical program · View on PubMed →
Bone and tissue effects in animals
In rodent studies, ipamorelin increased body weight gain and bone mineral content, consistent with sustained growth hormone and IGF-1 signalling. These findings are preclinical and have not been confirmed in controlled human trials.
Animal models · View on PubMed →
Warnings & cautions
- Not approved for human use in the United States, the European Union, the United Kingdom, Canada, or Australia. Its only late-stage human testing (for postoperative ileus) was discontinued.
- Banned in competitive sport by the World Anti-Doping Agency (WADA) under S2 (peptide hormones and growth-hormone secretagogues).
- Raises growth hormone and IGF-1, which is a theoretical concern for anyone with active or recent cancer, since GH and IGF-1 can promote cell growth.
- Common side effects include injection-site reactions, water retention or mild peripheral edema, headache, and transient lightheadedness.
- May affect blood sugar. Growth hormone can reduce insulin sensitivity, which is relevant for anyone with diabetes or impaired glucose tolerance.
- Source quality is uncontrolled. Products sold for “research” are not regulated and may contain incorrect doses, contaminants, or different compounds than labelled.
References
- Raun K, Hansen BS, Johansen NL, et al. (1998). Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology. PubMed
- Gobburu JV, Agersø H, Jusko WJ, et al. (1999). Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharmaceutical Research. PubMed
- Beck DE, Sweeney WB, McCarter MD, et al. (2014). Prospective, randomized, controlled, proof-of-concept study of ipamorelin for postoperative ileus. PubMed
- Johansen PB, Nowak J, Skjaerbaek C, et al. (1999). Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats. Growth Hormone & IGF Research. PubMed
Reference links resolve to PubMed search queries. Verify the specific PMID before citing.
Important: This page is educational and reference-only. Ipamorelin is not approved for human use and is prohibited in competitive sport. Nothing here is medical advice. Any research must comply with applicable laws and institutional review requirements. Consult a qualified healthcare professional before making decisions about your health.