Ipamorelin: benefits, side effects, dosage and what the research shows

Ipamorelin is a pentapeptide with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2. It came out of a Novo Nordisk chemistry programme that modified earlier growth hormone-releasing peptides (GHRPs), and was published in 1998 under the title “Ipamorelin, the first selective growth hormone secretagogue” ^[1].

It belongs to the same family as GHRP-2, GHRP-6 and hexarelin: small synthetic peptides that mimic ghrelin, the stomach hormone that stimulates GH release and appetite. What set ipamorelin apart in animal work was its selectivity. It is most often discussed alongside CJC-1295, a GHRH analogue that acts on a different pituitary receptor.

Chemically, ipamorelin was designed to be shorter and simpler than its predecessors. The Novo Nordisk team arrived at it by removing the central Ala-Trp pair from an earlier compound, GHRP-1, and then optimising the remaining structure. In anaesthetised rats it released GH with a potency and maximum effect comparable to GHRP-6, and in conscious pigs its effective dose for half-maximal GH release was about 2.3 nmol/kg, again similar to GHRP-6 ^[1]. It was therefore not more powerful than the older peptides; what distinguished it was what else it did, or rather did not do.

The ipamorelin peptide is now marketed for muscle gain, fat loss, sleep and recovery. None of those is an approved use, and none has been tested in a clinical trial. The only condition it was formally developed for in people was post-operative ileus, the temporary stalling of the gut after abdominal surgery, and that trial did not meet its main goal ^[11]. The rest of this guide sets out what ipamorelin does in the studies that exist, and where the claims made for it run beyond them.

Ipamorelin activates the growth hormone secretagogue receptor (GHS-R1a). That receptor was cloned in 1996 as the target of synthetic GH secretagogues ^[2], and its natural ligand, ghrelin, was identified three years later ^[3]. Stimulating the receptor on the pituitary and hypothalamus triggers a pulse of GH release.

In the original pharmacology study, ipamorelin released GH from rat pituitary cells with potency and efficacy similar to GHRP-6, and its effect was blocked by GHRP antagonists but not GHRH antagonists, confirming it works through the GHRP receptor rather than the GHRH receptor ^[1]. In pigs, GHRP-6 and GHRP-2 raised ACTH and cortisol, but ipamorelin did not, even at doses more than 200 times higher than those needed for GH release; it also left FSH, LH, prolactin and TSH unchanged ^[1]. This selectivity is the reason ipamorelin is often described as a “cleaner” GHRP. It was shown in animals, not in controlled human comparisons.

Because the GHRH and ghrelin-receptor pathways are separate, combining the two classes gives a greater-than-additive GH response. This was shown in an early study in men given GHRP-6 together with GHRH ^[4]. It explains the popularity of pairing ipamorelin with CJC-1295 or sermorelin, though no published human trial has studied ipamorelin in combination with either.

Much of ipamorelin’s preclinical research was on bone. In adult female rats injected three times daily for 15 days (total doses of 18, 90 or 450 µg per day), ipamorelin increased the rate of longitudinal bone growth and body-weight gain in a dose-dependent way, without changing total IGF-1 or markers of bone turnover ^[5].

Over 12 weeks of continuous infusion in young adult female rats, both ipamorelin and GHRP-6 (0.5 mg/kg per day) increased bone mineral content. Further analysis showed this reflected larger bones rather than denser bone: volumetric bone mineral density did not change ^[6]. In rats given a high-dose glucocorticoid (methylprednisolone) for three months, adding ipamorelin at 100 µg/kg three times daily counteracted the steroid-induced fall in muscle strength and bone formation ^[7].

Ghrelin also speeds up the gut, and this became ipamorelin’s main clinical target. In rats that had undergone abdominal surgery with bowel handling, a model of post-operative ileus, single intravenous doses of ipamorelin (1 mg/kg) shortened the time to first bowel movement, and repeated dosing over two days increased stool output, food intake and weight gain ^[8]. A separate rat study found that ipamorelin accelerated gastric emptying after abdominal surgery: with a single intravenous dose of 0.014 µmol/kg, 52% of a test meal remained in the stomach after 15 minutes, compared with 78% in untreated operated rats and 44% in rats without surgery. In isolated stomach muscle, ipamorelin and ghrelin both restored contractions that surgery had suppressed, pointing to a ghrelin-receptor effect on the nerves that drive gut muscle ^[9]. These results led directly to the human ileus trial described below.

The benefits most often claimed for ipamorelin (more lean muscle, less body fat, deeper sleep, faster recovery, slower ageing) all rest on one assumption: that raising the body’s own growth hormone will reproduce the effects of GH treatment. That chain has not been tested for ipamorelin in people. What exists is short-term hormone data in healthy men ^[10], one negative surgical trial ^[11] and a set of animal studies, grouped below by the use people ask about.

Muscle. The closest evidence comes from rats given high-dose steroids, which break down muscle protein. In one study, ipamorelin at 0.5 mg/kg per day for seven days reduced the liver’s capacity to turn amino acids into urea by 20%, neutralised the negative nitrogen balance caused by prednisolone, and normalised or improved the nitrogen content of several organs. GH itself had a stronger effect at the doses used ^[18]. In the methylprednisolone study described above, ipamorelin also counteracted the steroid-induced loss of muscle strength ^[7]. Neither study looked at muscle growth in healthy animals, and neither has been repeated in people.

Fat loss. Here the animal evidence points the other way. In mice injected twice daily under the skin, ipamorelin produced a small (15%) gain in body weight within two weeks and raised fat pad weight relative to body weight, in both GH-deficient and GH-intact animals. Two weeks of ipamorelin or GHRP-6 also increased relative body fat measured by DEXA scanning in normal mice. Unlike GH, the secretagogues increased food intake and leptin, and the authors concluded that they add body fat through mechanisms that do not depend on GH, possibly including extra feeding ^[17]. That runs counter to the fat-loss claim.

Bone and gut effects are covered in the two sections above. For sleep, injury recovery, skin or hair, we found no published ipamorelin study in animals or people.

Apart from anti-doping studies of how it is metabolised, only two clinical studies of ipamorelin have been published. The first is a dose-escalation pharmacokinetic study in healthy men, with eight volunteers at each of five dose levels, who received 15-minute intravenous infusions. Ipamorelin had a short terminal half-life of about two hours, and each dose produced a single episode of GH release peaking at about 0.67 hours (40 minutes), then declining to negligible levels ^[10].

The second is a phase 2, multicentre, double-blind, placebo-controlled proof-of-concept trial in 117 adults undergoing bowel resection. Patients received intravenous ipamorelin or placebo twice daily for up to seven days after surgery. Ipamorelin was well tolerated, with treatment-emergent adverse events in 87.5% of the ipamorelin group and 94.8% of the placebo group, but it did not significantly shorten the time to tolerating a solid meal (median 25.3 hours versus 32.6 hours; p = 0.15), and secondary outcomes also showed no significant difference ^[11].

There are no published human trials of ipamorelin for body composition, muscle, fat loss, sleep, recovery or ageing. The claims made for those uses rest on its ability to raise GH in short-term studies and on the animal work above.

The only human timing data are hormonal and measured in minutes. In the pharmacokinetic study, a 15-minute intravenous infusion produced a single GH episode that peaked at about 40 minutes and then fell to negligible levels, at every dose tested ^[10]. The published abstract reports GH only. There are no published human data on how IGF-1, body composition, strength or any other outcome changes over weeks of ipamorelin use, so any stated results timeline is not based on research.

Animal studies give a sense of time scale, not of human results. Faster longitudinal bone growth in rats was measurable after 15 days ^[5], weight and fat gain in mice appeared within two weeks ^[17], and changes in bone mineral content were assessed after 12 weeks of infusion ^[6]. The surgical trial followed patients for the first week after their operation and found no significant difference from placebo in gut recovery ^[11].

Searches for ipamorelin before and after photos lead mostly to testimonials. These are uncontrolled: product content is unverified, and diet or training usually changes at the same time. A 2026 sports-medicine review also discusses how the placebo effect, amplified by social media, shapes perceived results from peptides ^[32].

Ipamorelin is commonly discussed in combination with CJC-1295. The logic is pharmacological. Ipamorelin acts on the ghrelin receptor and CJC-1295 on the GHRH receptor, two separate inputs that the pituitary integrates. Human studies of older compounds showed that giving a GH-releasing peptide together with GHRH releases more GH than either alone, and more than their sum ^[4]. Pairing a selective ghrelin mimetic with a long-acting GHRH analogue is an extrapolation from that finding. Everything published on the pairing is collected in CJC-1295 and ipamorelin.

It is only an extrapolation. We found no published human study of ipamorelin combined with CJC-1295, whether the DAC version or the no-DAC version sold as Modified GRF (1-29), and no study of the combination’s effect on body composition, sleep or any other outcome. The doses circulated online for this combination do not come from clinical trials. Anyone comparing products should also be aware that “CJC-1295” can refer to two different molecules; our CJC-1295 guide explains the difference.

Why the two classes should cooperate is clearer from an unusual group of patients. Men with an inherited defect in the GHRH receptor had no GH response at all to the GH-releasing peptide hexarelin, although their prolactin, ACTH and cortisol still rose normally. The authors concluded that GH-releasing peptides need a working GHRH signalling system to release GH ^[20]. GH-releasing peptides have also been proposed to work partly by counteracting somatostatin, the hypothalamic brake on GH release ^[33]. On that view, a GHRH analogue supplies the signal that a ghrelin mimetic amplifies.

Synergy is not guaranteed in every study. When eight healthy young men were given intravenous GHRP-2 and GHRH(1-29) together, the GH response was larger than with GHRP-2 alone but no greater than the sum of the two given separately ^[21]. Results with one GH-releasing peptide and one form of GHRH cannot simply be carried over to ipamorelin and CJC-1295.

Which CJC-1295 is used also matters. A 2026 clinical review notes that in fitness settings ipamorelin is typically combined with the no-DAC form ^[12], which has no published human data. The DAC form, which has been studied, raised GH and IGF-1 for about a week after a single injection ^[22], while ipamorelin’s GH pulse is over within hours ^[10]. The two products have very different time profiles, and no study has measured what happens when they are given together.

Because the pair has never been trialled, there is no researched CJC-1295 ipamorelin dosage, no measured results timeline and no side-effect data for the combination. Readers should expect the reported effects of each class, such as fluid retention, joint and muscle aches, injection-site reactions and changes in glucose ^[12], without assuming that combining them is either safer or more effective. Pre-mixed blend vials (for example 10 mg vials holding both peptides) add another unknown, because the ratio is set by the seller and cannot be checked without an independent assay. Use the peptide calculator for concentration arithmetic and CJC-1295 prices for cost comparisons.

Tesamorelin is a GHRH analogue, like CJC-1295, but unlike CJC-1295 it is an approved medicine. Its FDA label describes it as the full 44-amino-acid sequence of human GHRH with a hexenoyl group attached, approved to reduce excess abdominal fat in adults with HIV and lipodystrophy ^[26]. Blends of tesamorelin and ipamorelin, sometimes with a third peptide such as Mod GRF 1-29 or MGF, are sold online on the same logic as CJC-1295 and ipamorelin. Our Tesamorelin vs ipamorelin comparison sets the two side by side.

No study has tested a tesamorelin ipamorelin blend. The only established tesamorelin doses are those on its label for its approved use: 1.28 mg once daily under the skin for the Egrifta WR formulation ^[26], and 2 mg daily in the phase 3 trial of the original formulation ^[25]. Dosage charts for these blends are not derived from research on the combination. In August 2026 the FDA issued a warning letter to an online seller whose products included tesamorelin and ipamorelin, stating that “research use only” labelling did not stop them from being unapproved drugs ^[28].

Sermorelin and ipamorelin are compared because both are promoted as ways to raise the body’s own GH rather than injecting GH itself. They act through different receptors. Sermorelin is GHRH(1-29), the shortest synthetic fragment of GHRH with full activity, and acts on the GHRH receptor ^[23]; ipamorelin acts on the ghrelin receptor ^[1]. In principle the two could be complementary, which is why sermorelin and ipamorelin blends exist, but no study has tested them together. Our Ipamorelin vs sermorelin comparison sets the two side by side.

Their evidence differs more than their mechanism. Sermorelin was a licensed US medicine (Geref) for testing and treating GH deficiency in children; once-daily injections of 30 µg/kg increased height velocity in prepubertal children with idiopathic GH deficiency, and transient facial flushing and injection-site pain were the most common adverse events ^[23]. The manufacturer discontinued it in 2008, and the FDA later determined that it had not been withdrawn for reasons of safety or effectiveness ^[24]. Ipamorelin was never licensed, and its only efficacy trial was negative ^[11]. The two have never been compared head to head. Our sermorelin guide covers its trials in detail.

This is the most searched comparison, and the most uneven in evidence. Tesamorelin has phase 3 data: in a 26-week trial in 412 people with HIV and excess abdominal fat, 2 mg daily reduced visceral fat by 15.2% while it rose by 5.0% on placebo, and IGF-1 increased by 81% ^[25]. It is approved for that indication only, and its label states that it is not indicated for weight loss management ^[26]. Ipamorelin has no comparable trial for any body-composition outcome.

The two also behave differently in the body. Tesamorelin works through the GHRH receptor and had an elimination half-life of 11 minutes after injection in healthy subjects ^[26]; ipamorelin works through the ghrelin receptor and had a half-life of about two hours after intravenous infusion ^[10]. For anyone weighing tesamorelin vs sermorelin vs ipamorelin, the first two are GHRH analogues with regulatory histories and the third is a ghrelin mimetic without one. See our tesamorelin guide for its trials and label.

Among the ghrelin-receptor peptides, ipamorelin was the most selective in animal studies but not the most potent. In conscious pigs, GHRP-2 was more potent but produced a lower maximum GH response, ipamorelin behaved much like GHRP-6 for GH, and only ipamorelin left ACTH and cortisol unchanged ^[1]. In rats, ipamorelin was cleared from the blood about five times more slowly than GHRP-6 and was excreted mainly in urine rather than bile ^[16]. Human comparisons are lacking; the older peptides are covered in our GHRP-2 and hexarelin guides.

Every published human study of ipamorelin used intravenous infusion ^[10][11]. There are no published human data on subcutaneous injection, so questions such as where to inject ipamorelin, or whether a pen behaves differently from a vial, have no research answer. Research suppliers sell it as freeze-dried powder.

Nasal delivery was explored in animals. In rats, the nasal bioavailability of ipamorelin was estimated at about 20%, lower than the roughly 50% measured for GHRP-2, and the authors judged the nasal route promising for this family of peptides ^[16]. An anti-doping study gave nasal ipamorelin to a single volunteer to map its urinary breakdown products; a fragment, ipamorelin (1-4) free acid, was still detectable after the parent peptide had cleared ^[19]. That shows the peptide is absorbed through the nose but says nothing about the size of any GH response. We found no published study of oral ipamorelin, tablets or capsules.

In healthy men, the pharmacokinetic study used intravenous infusions of 4.21, 14.02, 42.13, 84.27 and 140.45 nmol/kg over 15 minutes ^[10]. The post-operative ileus trial used 0.03 mg/kg intravenously twice daily for up to seven days ^[11]. Both were hospital-administered intravenous regimens, not the subcutaneous injections used by people self-administering the peptide.

Animal studies used, for example, 18 to 450 µg per day in rats ^[5], 0.5 mg/kg per day by infusion in rats ^[6], and 0.01 to 1 mg/kg intravenously in the rat ileus model ^[8]. These are animal doses and should not be converted to human doses. No subcutaneous human dose has been established in a published trial. For laboratory reconstitution arithmetic, see our peptide calculator.

No published study supports an ipamorelin dosage per day, a timing schedule or a dosage chart for self-administration. The charts found online come from sellers and forums, not trials, and a 2026 clinical review draws the same line between peer-reviewed data and online protocols ^[12].

Questions about ipamorelin dosage in ml, or how many units to draw, are arithmetic rather than research questions. Concentration is the amount of peptide in the vial divided by the volume of liquid added. For example, 10 mg dissolved in 2 mL of bacteriostatic water gives 5 mg/mL, or 5,000 µg per mL. On a U-100 insulin syringe, where 100 units equal 1 mL, each unit then holds 50 µg. The same method works for a 5 mg vial or any other volume. It says nothing about what amount is appropriate, which no trial has established for subcutaneous use.

In the phase 2 surgical trial, the overall rate of adverse events was similar to, and numerically lower than, placebo, in a population recovering from major surgery ^[11]. The pharmacokinetic study’s abstract does not report adverse events in detail ^[10]. Human safety data therefore come from short courses of intravenous dosing in hospital settings, with no long-term information and nothing on repeated subcutaneous use.

Ipamorelin’s reputation for not raising cortisol or prolactin comes from pig studies ^[1]; it has not been confirmed in a published head-to-head human study. As a ghrelin-receptor agonist it may be expected to increase appetite, as GHRP-2 does in people, but this has not been measured for ipamorelin in humans ^[15]. A 2026 clinical review of GH-axis peptides groups ipamorelin with other secretagogues whose reported adverse effects include hormonal and glucose changes, fluid retention, joint and muscle pain and injection-site reactions, and notes that the content of unregulated products is uncertain ^[12].

The same review describes ipamorelin’s sparing of cortisol and prolactin in people as theoretical rather than characterised, because the evidence comes from animals ^[12]. In mice, ipamorelin increased food intake and body fat ^[17], which is relevant to anyone expecting weight loss. Long-term effects, including any effect on cancer risk from sustained rises in GH and IGF-1, have not been studied; the review calls such mitogenic concerns biologically plausible but unproven ^[12]. Anti-doping laboratories have also found modified ipamorelin analogues in seized products ^[14], so a vial may not contain what its label says.

Ipamorelin is not an approved medicine in the UK, US, Canada, Australia or New Zealand. It is sold as a research chemical, and its legal position for buyers differs by country; see our legal status overview and the UK and US pages.

Ipamorelin is named on the WADA Prohibited List under S2 as a growth hormone secretagogue and is banned at all times ^[13]. Anti-doping laboratories have also identified glycine-extended versions of ipamorelin in black-market products ^[14].

On the question of FDA approval status, the FDA has gone further than simply not approving it. As of April 2026, ipamorelin acetate remains in Category 2 of the FDA’s list of bulk drug substances for compounding, the group it describes as possibly presenting significant safety risks ^[27]. In an August 2026 warning letter to an online seller, the FDA said that “research use only” labels did not stop peptide products, including ipamorelin, from being treated as unapproved drugs ^[28].

Other regulators have named it directly. Health Canada’s April 2026 advisory on injectable peptides listed ipamorelin among seized unauthorised products and said research-use labelling does not make them legal ^[29]; see our Canada page. In Australia, the June 2026 Poisons Standard lists ipamorelin as a prescription-only (Schedule 4) substance in Appendix D, whose entries must not be possessed without authority ^[30]. In New Zealand, Medsafe classifies ipamorelin as a prescription medicine ^[31].

Research-grade ipamorelin is supplied as freeze-dried powder. No stability data have been published for these products; general practice for lyophilised peptides is covered in our guide to storing peptides.

Ipamorelin is one of the most widely stocked research peptides. Compare prices, check the certificate of analysis with our guide on how to read a COA, and prefer third-party tested suppliers. Given the modified analogues found in seized products ^[14], a COA with a mass-spectrometry identity check is particularly useful.

Listings are usually sold as 5 mg or 10 mg vials, and price per milligram varies by market; see ipamorelin UK prices and ipamorelin in Australia, bearing in mind the legal points above. Our guide to third-party peptide testing explains what an independent lab report can and cannot confirm.