Ipamorelin: the monograph

Ipamorelin is a synthetic five-amino-acid peptide that makes the pituitary release a pulse of the body's own growth hormone. It does this by activating the ghrelin receptor, the same receptor targeted by the hunger hormone¹. Clinics and research-chemical vendors sell it as the cleanest or most selective of the growth hormone peptides, usually paired with CJC-1295.

Three facts frame everything else on this page. First, ipamorelin is not FDA approved for anything, anywhere: a Drugs@FDA search returns no product containing it⁴. Second, FDA placed ipamorelin acetate in Category 2 of its compounding lists on September 29, 2023, the category for bulk substances that may present significant safety risks³. Third, and least advertised: ipamorelin is not an undiscovered frontier compound. It was a real drug candidate, developed by Novo Nordisk in the 1990s under the code NNC 26-0161 and taken into phase 2 human trials for a hospital indication by Helsinn. The randomized trial that reported results found no significant benefit, the larger follow-up trial was never published, and the program stopped⁵⁷.

This monograph documents that history with primary sources: the selectivity pharmacology at its true evidence grade, the complete human trial record, the animal literature the marketed benefits actually trace to, and what remains unknown. Our evidence table holds 16 study rows, each labeled by species; 3 are human, and none of the human rows tests muscle gain, fat loss, anti-aging or recovery²⁵.

Ipamorelin is a pentapeptide with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2, molecular formula C38H49N9O5 and molecular weight 711.9 (PubChem CID 9831659; CAS 170851-70-4)⁸. Two of its five residues are unnatural amino acids, a design choice that raised its stability and, in FDA's later assessment, adds to the complexity of characterizing compounded versions³.

The molecule came out of a deliberate medicinal-chemistry program at Novo Nordisk: the team removed the central Ala-Trp dipeptide of GHRP-1 and screened the resulting series, publishing the result in 1998 as the first growth hormone secretagogue with GHRH-like selectivity¹. Its internal code, NNC 26-0161, appears throughout the primary literature and in chemical registries¹⁰⁸. Despite the marketing category it now lives in, ipamorelin is not a fragment of any human hormone. It is a designed drug molecule whose development was later abandoned.

Ipamorelin's history is the strongest argument against the way it is marketed, so we lay it out in order.

1994 to 1998: a real discovery program. Novo Nordisk's growth hormone group designed ipamorelin, characterized it in vitro, in rats and in swine, and published the selectivity result that still powers every sales page today¹. The company valued the scaffold enough to build follow-on series from it, seeking orally available successors; in dogs, oral ipamorelin itself raised basal GH more than 10-fold at 2.7 mg/kg, and a derived tetrapeptide reached 10% oral bioavailability⁹. Rat pharmacokinetics, including a nasal-absorption estimate of roughly 20%, were published the same year¹⁰.

1999: the only human pharmacology ever published. A dose-escalation study infused ipamorelin intravenously in healthy men, eight subjects per dose across five dose levels, establishing a 2-hour half-life and a single clean pulse of GH peaking about 40 minutes after dosing². No human study of repeated dosing has ever been published.

2008 to 2014: the clinical program, and its end. Helsinn took ipamorelin into phase 2 for postoperative ileus, the gut shutdown that follows bowel surgery, on the strength of rodent motility data¹⁶¹⁷. The proof-of-concept trial (NCT00672074) randomized 117 patients to 0.03 mg/kg intravenously twice daily or placebo: median time to first tolerated meal was 25.3 hours on drug versus 32.6 on placebo, p = 0.15, with no significant differences on any key or secondary efficacy analysis⁵⁶. A second, larger dose-finding trial (NCT01280344) enrolled 320 patients across three regimens and completed in May 2014⁷. Its results were never posted to the registry and, as of August 14, 2026, no publication reporting them exists among the 54 ipamorelin records in PubMed⁷. A 2026 endocrinology review states the proof-of-concept failure "tempered further clinical investigation"²².

What that sequence means. A pharmaceutical company with the molecule's inventor, a specialty developer, two phase 2 trials and roughly twenty years had every incentive to demonstrate a use for ipamorelin. The one randomized result made public is negative, the larger dataset is dark, and no company is developing the compound today in any indexed trial⁶⁷. The vials sold online are not early access to a coming therapy. They are the aftermarket of a program that ended.

Ipamorelin is an agonist of the growth hormone secretagogue receptor (GHS-R1a), the receptor for ghrelin. Activating it triggers the pituitary to release a pulse of growth hormone; in the human study, a single intravenous dose produced one episode of GH release that peaked at about 0.67 hours and then declined to negligible levels, at every dose tested². The concentration for half-maximal GH stimulation was 214 nmol/L².

Its potency was defined in animals: EC50 of 1.3 nmol/L in rat pituitary cell culture, ED50 of 80 nmol/kg in anaesthetised rats and 2.3 nmol/kg in conscious swine, all comparable to GHRP-6¹. Because it works through the ghrelin receptor, ipamorelin carries ghrelin-like baggage that marketing rarely mentions: in mice it increased body fat, leptin and food intake through mechanisms independent of GH¹⁸, and in rat pancreatic tissue it directly stimulated insulin release¹⁹. A ghrelin mimetic is, mechanistically, an appetite-axis drug as much as a growth-hormone one.

The claim that ipamorelin is the cleanest GH peptide is not invented. It has a real source, and the source has a real grade: swine.

In the 1998 Novo Nordisk study, older secretagogues (GHRP-2, GHRP-6) raised ACTH and cortisol alongside GH. Ipamorelin did not: in swine, ACTH and cortisol stayed at levels no different from GHRH stimulation even at doses more than 200-fold above the GH ED50, and none of the compounds tested moved FSH, LH, prolactin or TSH¹. That is a genuinely distinctive pharmacological profile, and it is why the paper's title calls ipamorelin the first selective GH secretagogue¹.

In humans, the footprint is thinner than the marketing implies. The single-dose intravenous study is summarized in a 2026 review as showing no significant effects on other pituitary or adrenal hormones in that setting; the same review classifies ipamorelin's cortisol and prolactin sparing under chronic use as theoretical and not characterised, and observes that the cleaner endocrine profile "is often presented as a practical distinction" in how these compounds are sold²². No published human study has measured cortisol or prolactin under weeks of repeated dosing, because no such study exists for any endpoint²².

So the honest version of the selectivity claim reads: demonstrated at single doses in animals at up to 200-fold the effective dose; consistent with the one human single-dose study; never tested in humans under the chronic dosing schedules actually used by buyers¹²².

The published human record on ipamorelin consists of exactly two things.

1. Pharmacokinetics in healthy men (1999). Five ascending intravenous infusion rates, 4.21 to 140.45 nmol/kg over 15 minutes, eight healthy male subjects per level. Results: dose-proportional kinetics, terminal half-life about 2 hours, clearance 0.078 L/h/kg, a single GH pulse peaking at 0.67 hours². This study measured hormones, not outcomes.

2. The postoperative ileus program (2008 to 2014). One published randomized trial in 117 bowel-resection patients: no significant benefit on any efficacy endpoint (median time to first tolerated meal 25.3 vs 32.6 hours, p = 0.15)⁵. One completed but unpublished 320-patient dose-finding trial⁷.

That is the entire interventional record. There is no human trial of ipamorelin for muscle, fat loss, body composition, skin, sleep, recovery, injury, longevity or any of the goals it is sold for; a 2020 review of secretagogues in men's health describes a paucity of clinical-effect data for the class, and a 2026 review finds evidence in non-approved indications remains minimal²³²². Where a clinic quotes body-composition numbers at you, ask which compound they belong to: for ipamorelin, none exist.

The benefit claims attached to ipamorelin trace almost entirely to a cluster of rodent studies, most of them from the original Novo Nordisk program. They are real studies with real effects, in animals, at doses far above anything humans inject.

Bone and growth. In rats, 15 days of subcutaneous ipamorelin dose-dependently raised longitudinal bone growth rate from 42 to up to 52 micrometers per day and increased weight gain, without moving IGF-I¹¹. Twelve weeks of 0.5 mg/kg/day increased bone mineral content in adult female rats, but by making bones bigger, not denser: volumetric density was unchanged¹².

Steroid-catabolism models. In rats given glucocorticoids, ipamorelin preserved the GH response, restored muscle tetanic tension, quadrupled periosteal bone formation versus steroid alone, reduced steroid weight loss, and partially corrected nitrogen wasting (20% reduction in hepatic urea-nitrogen synthesis capacity, versus 33% for GH itself)¹³¹⁴¹⁵.

Gut motility. The rodent work that launched the clinical program: single intravenous doses shortened time to first bowel movement and accelerated gastric emptying in surgical-ileus models¹⁶¹⁷. This is the one area where the animal-to-human translation was actually tested, and it failed⁵.

Appetite, fat and insulin. The inconvenient rows: in mice ipamorelin increased body fat, leptin and food intake by GH-independent mechanisms¹⁸; in rat pancreas it stimulated insulin release from normal and diabetic tissue¹⁹; in ferrets it reduced chemotherapy weight loss by about 24%, the class effect that made its cousin anamorelin a cachexia drug²¹. A ghrelin agonist's natural direction is weight gain.

Ipamorelin is most often sold stacked with CJC-1295. The rationale is mechanistic: CJC-1295 is a long-acting GHRH analog (half-life 5.8 to 8.1 days in the human trial) that raises baseline GH and IGF-I for days²⁹, while ipamorelin is a short-acting ghrelin-receptor agonist producing a single 2-hour pulse². Two receptors, two time courses; the theory is that together they amplify GH release.

Here is the evidentiary status of that theory in humans: no randomized trial of the combination exists for any endpoint. A 2026 review states the pairing "is largely driven by anecdotal rationale" without controlled clinical evidence of synergy²². Each half also carries its own regulatory freight: FDA has placed both compounds on its compounding safety-risk list, citing for CJC-1295 reports of serious adverse events including increased heart rate and systemic vasodilatory reaction³.

Our sister site covers CJC-1295 with the same standards; the comparison table below is the short version. The combination's popularity is a marketing architecture, not a data architecture: two abandoned or never-developed compounds packaged so that each covers the other's gap²²³.

No dose of ipamorelin has ever been shown effective for any condition in humans, so there is no such thing as an evidence-based ipamorelin dose. What exists is a studied-dose record and a folklore record, and they do not match.

Studied in humans. The PK study infused 4.21 to 140.45 nmol/kg intravenously over 15 minutes as single doses (for a 70 kg adult, roughly 0.2 to 7 mg, using the 711.9 g/mol molecular weight)²⁸. The ileus trials used 0.03 mg/kg intravenously twice daily (about 2.1 mg per dose at 70 kg), with the unpublished trial adding 0.06 mg/kg arms twice and three times daily⁵⁷. These were hospital infusions in monitored patients, and the tested indication failed⁵.

Folklore. Bodybuilding forums, as documented in the 2026 review, run 200 to 300 micrograms subcutaneously two or three times daily, cycled 8 to 12 weeks, usually with CJC-1295²². Note what that means: the internet's standard protocol is a chronic subcutaneous schedule that no published human study has ever used, at roughly a tenth of the single trial dose, for goals no trial has tested²²². Subcutaneous ipamorelin pharmacokinetics have never been published in humans at all.

Our dose explorer tool lists every studied dose row with its species, so the distance between the literature and the folklore is visible at a glance. We do not recommend doses; there is nothing evidence-based to recommend.

Unknown at the schedules people actually use. That is the honest one-line answer, and here is what stands behind it.

What human data exist. In the published trial, one week of intravenous ipamorelin in postsurgical patients produced treatment-emergent adverse events in 87.5% of drug patients versus 94.8% on placebo, and the authors called it well tolerated in that setting⁵. Single intravenous doses in healthy men raised GH without other reported hormone effects²²². No human safety data exist for chronic subcutaneous use, the way it is actually taken²².

What FDA flagged. Immunogenicity risk from aggregation and peptide-related impurities; characterization complexity from the unnatural amino acids; a literature report of serious adverse events including death with intravenous use in the gastric-motility program; and, for other injectable routes, insufficient information to know whether the drug would cause harm³. The death language refers to trials in seriously ill surgical patients, a population with substantial background mortality; the published trial reported similar adverse-event rates in both arms⁵. Neither fact cancels the other: FDA's conclusion was that the safety picture is insufficient, not reassuring.

Mechanism-level cautions. Ghrelin-receptor agonism stimulated insulin release in rat pancreatic tissue¹⁹ and increased fat and food intake in mice¹⁸; GH-axis stimulation raises the standing class questions about glucose tolerance and growth-sensitive tissue that apply to every secretagogue²⁴. Product quality is its own hazard: forensic analyses of seized products found glycine-modified ipamorelin analogs rather than the labeled compound²⁵²⁶.

No label exists, so no contraindication list exists; what follows is class reasoning from the GH axis, stated as such.

Anyone with an active malignancy or a cancer history sits in the highest-caution group: the one approved GHRH-analog product, tesamorelin, is contraindicated in active malignancy, and growth-axis stimulation is the shared mechanism³³. People with diabetes or impaired glucose tolerance should note both the class glucose effects and ipamorelin's direct insulin-release signal in rat pancreas¹⁹²⁴. Pregnancy and breastfeeding have zero data of any kind²². And anyone subject to anti-doping rules is prohibited from using it at all times²⁷.

No human interaction study has ever been conducted, so this section reports mechanism-level signals from animal work, labeled as such.

Glucose-lowering medicines: ipamorelin stimulated insulin secretion directly from rat pancreatic tissue through calcium-channel and adrenergic pathways¹⁹, and GH itself is counter-regulatory to insulin; the net effect of the two directions in a medicated human is unstudied. Glucocorticoids: in rats, methylprednisolone did not blunt the GH response to ipamorelin, and ipamorelin partially offset steroid catabolism¹⁴¹⁵; this is pharmacology, not a demonstrated clinical benefit. Appetite-active drugs: ghrelin-receptor agonism increased food intake in mice¹⁸. Nothing is known about interactions with any specific human medication²².

There are no human pregnancy data, no lactation data and no developmental toxicity publications for ipamorelin in the indexed literature as of this writing²². The compound was abandoned before any such program would have run. This is a complete unknown, on top of a compound whose adult safety is itself insufficiently characterized in FDA's assessment³.

Honestly: nobody can tell you with authority, because no approved product and no label exist⁴. The published human studies used intravenous infusions prepared for a hospital setting²⁵; they are not a template for vial storage at home. What circulates commercially is lyophilized powder of research-chemical grade, and forensic analyses of seized products in this class found modified analogs rather than the labeled peptide, which is a sharper problem than storage temperature²⁶²⁵. Any storage guidance you see on a vendor page is the vendor's assertion, not a validated standard.

Ipamorelin sits in what a 2026 sports-medicine review calls a parallel gray market operating largely outside regulatory oversight²⁴. Two forensic findings show what that means in practice. German and Norwegian doping-control laboratories analyzing black-market growth products identified Gly-Ipamorelin, an ipamorelin analog carrying an extra N-terminal glycine, confirmed by custom synthesis²⁵. Danish customs seizures of unlabeled powders likewise contained glycine-modified analogs of ipamorelin, GHRP-2, GHRP-6 and modified GRF 1-29²⁶.

These analogs are not the studied molecule: their pharmacology and immunogenicity are uncharacterized, which is precisely the impurity-and-characterization risk FDA cited when it placed ipamorelin acetate in Category 2³. A certificate of analysis from the seller is a self-issued document; the seized-product literature is what independent laboratories actually found.

Ipamorelin is prohibited at all times, in and out of competition, under the WADA Prohibited List: section S2.2.4 names it explicitly among growth hormone secretagogues and their mimetics, alongside anamorelin, ibutamoren and ghrelin itself²⁷. CJC-1295, sermorelin and tesamorelin are banned in the same section as GHRH analogues, so the popular stack is prohibited twice over²⁷. Anti-doping laboratories publish detection methods for ipamorelin and its metabolites in urine, and the glycine-modified analogs found in seized products were characterized specifically so screens could catch them²⁶²⁵.

The human numbers all come from one intravenous study in healthy men²: terminal half-life about 2 hours; clearance 0.078 L/h/kg; steady-state volume of distribution 0.22 L/kg; dose-proportional exposure; a single GH pulse peaking at 0.67 hours and returning to negligible levels; half-maximal GH stimulation at an ipamorelin concentration of 214 nmol/L².

Animal kinetics add texture the human study could not: in rats, ipamorelin cleared 5-fold more slowly than GHRP-6, was excreted largely intact in urine, and reached about 20% bioavailability through the nasal route¹⁰. Two gaps matter for anyone reading vendor pages: subcutaneous pharmacokinetics have never been published in humans, and neither has any multiple-dose kinetic study²²².

The list of unknowns is most of the map. No human efficacy has been demonstrated for any use: the one indication ever tested in a randomized trial, postoperative ileus, showed no significant benefit, and the larger trial's results were never made public⁵⁷. Nothing is known from human trials about effects on muscle, fat, body composition, skin, sleep, recovery or aging²³²². Chronic-use selectivity (cortisol, prolactin), chronic-use safety, subcutaneous kinetics, long-term glucose effects, immunogenicity of repeated injections, cancer-relevant effects of sustained GH-axis stimulation and every drug interaction are unstudied²²³. IGF-I responses under the internet's chronic schedules have never been measured in a published study²². Where ipamorelin marketing quotes benefit numbers, they trace to rat and mouse studies from the abandoned development program, or to studies of other compounds entirely¹¹¹².

Every claim on this page carries a numbered citation that resolves to a primary source: peer-reviewed journals, FDA pages, ClinicalTrials.gov records, PubChem and the WADA Prohibited List. The full numbered list is below, and the same data ships as a machine-readable manifest at /evidence.json. Where a free full text exists, the citation links it.

Direct answers to the questions readers actually bring to ipamorelin, each with its sources; the short version of every answer comes first.

Ipamorelin lives inside a family of GH-axis molecules that marketing blurs together and pharmacology separates. CJC-1295, its usual stacking partner, is a GHRH analog with a days-long half-life, studied in healthy adults but never approved²⁹. Sermorelin is the GHRH fragment that briefly was an approved drug; FDA determined its withdrawal was not about safety or effectiveness³². Tesamorelin is the one GHRH analog with a current FDA approval, for a single HIV-associated indication³³. Ipamorelin works on a different receptor from all three: the ghrelin (GH secretagogue) receptor¹. Our comparison tables below hold the cited details, and each compound's sister site documents it at full depth.