Ipamorelin vs sermorelin: two routes to growth hormone release

The two are often listed side by side as “GH peptides”, which hides how different they are. Sermorelin is a hormone fragment, 29 amino acids long, that mimics the brain’s own GH-releasing signal. Ipamorelin is a five-amino-acid designer molecule that mimics a stomach hormone, ghrelin. One had a licence and a paediatric trial programme; the other went through a pharmacokinetic study and a single phase 2 trial.

What they share is the end result that was measured in people: a short rise in growth hormone (GH). Neither has been tested in adults for muscle, fat loss, sleep or ageing in a trial of meaningful size, and they have never been compared head to head. Full profiles are in our ipamorelin guide and sermorelin guide.

Somatotroph cells in the pituitary respond to two separate stimulating inputs. The first is GHRH, made in the hypothalamus, acting on the GHRH receptor; sermorelin plugs into this one ^[4]. The second is the growth hormone secretagogue receptor, GHS-R1a, cloned in 1996 as the target of synthetic GH-releasing compounds ^[11]; ghrelin is its natural ligand, and ipamorelin is one of the synthetic agonists.

Novo Nordisk’s 1998 pharmacology paper confirmed the split. Ipamorelin’s GH release from rat pituitary cells was blocked by an antagonist of the GHRP receptor but not by a GHRH antagonist ^[1]. So the two peptides are not stronger and weaker versions of one thing; they are different signals that converge on the same cell.

Ipamorelin lasts longer in the blood. In a five-level dose-escalation study, eight healthy men per level received 15-minute intravenous infusions; the terminal half-life was about two hours, and each dose produced a single GH episode that peaked at about 0.67 hours and then declined to negligible levels ^[2].

Sermorelin’s sequence is cleared in minutes. When ten healthy men received GHRH(1-29) by constant intravenous infusion, it disappeared from plasma with a half-time of about 4.3 minutes ^[8]. The practical consequence showed up in older men: 1 mg twice a day for two weeks raised IGF-1 to young-adult levels ^[6], but 2 mg once each night for six weeks increased night-time GH without changing IGF-1 ^[7].

Neither of these is a long-acting peptide. If a sustained signal is the question, the molecule people usually mean is CJC-1295 with DAC, a modified GHRH fragment that binds albumin.

Ipamorelin’s reputation rests on selectivity. In conscious pigs, GHRP-6 and GHRP-2 raised ACTH and cortisol, while ipamorelin did not, even at doses more than 200 times its half-maximal dose for GH release; none of the compounds changed FSH, LH, prolactin or TSH ^[1]. This was an animal finding and has not been confirmed in a controlled human comparison. For context, the older hexapeptide GHRP-6 roughly doubled prolactin and cortisol in healthy men, but only at its highest dose ^[10].

GHRH has a signature effect of its own. In the same 1990 study, 16 of 18 men given full-length GHRH intravenously had one to three minutes of mild facial flushing ^[10], and flushing was one of the two most commonly reported side effects of sermorelin ^[4].

Appetite is the other point of difference. Ghrelin-receptor agonists can make people hungrier: healthy men infused with GHRP-2 ate roughly a third more at a buffet meal than they did on saline ^[12]. Whether ipamorelin does the same in people has not been measured, and appetite was not reported as an effect in the sermorelin studies cited here ^[4][5].

Ipamorelin’s clinical development aimed at the gut rather than growth. A phase 2, double-blind, placebo-controlled trial randomised 117 adults after bowel resection to intravenous ipamorelin 0.03 mg/kg or placebo twice daily for up to seven days. It was well tolerated, but the median time to tolerating a solid meal, 25.3 hours versus 32.6 hours, was not significantly different, and neither were the secondary outcomes ^[3]. No further efficacy trial has been published.

Sermorelin’s trials were in GH deficiency. In 110 untreated prepubertal children given 30 µg/kg under the skin at bedtime, height velocity nearly doubled over the first six months, from 4.1 to 8.0 cm a year ^[5]. A 1999 review judged it a useful diagnostic test at a single intravenous dose of 1 µg/kg, noted that its growth responses fell short of those seen with daily recombinant GH, and said its effect on final height had not been established ^[4]. The adult data amount to the two small studies in older men described above ^[6][7].

The FDA first approved sermorelin acetate, under the Geref name, as a diagnostic in December 1990 and as a paediatric treatment for idiopathic GH deficiency in September 1997. EMD Serono discontinued it in 2008, the FDA withdrew the approvals from 18 June 2009, and in 2013 the agency determined that the product had not been withdrawn for safety or effectiveness reasons ^[9].

Ipamorelin has never been approved anywhere in our markets. As of April 2026, ipamorelin acetate was still in the FDA’s category of compounding substances flagged for possible significant safety risks ^[15]. Health Canada’s April 2026 advisory named ipamorelin among seized unauthorised peptides ^[17], and Medsafe’s classification database lists both ipamorelin and sermorelin as prescription medicines in New Zealand ^[16]. See our legal status overview and the UK legal status page for the rules in each market.

Ipamorelin’s human doses were all intravenous. The pharmacokinetic study used infusions of 4.21 to 140.45 nmol/kg over 15 minutes ^[2], and the surgical trial used 0.03 mg/kg twice daily ^[3]. No subcutaneous human dose has been established in a published trial.

Sermorelin’s doses were subcutaneous apart from the diagnostic test: 30 µg/kg at bedtime in children ^[5], 0.5 mg or 1 mg twice daily in older men ^[6], and 2 mg once nightly in another group of older men ^[7]. These are reported for information, not as recommendations. Converting milligrams to volumes is covered by our peptide calculator, and mixing liquids by our guide to bacteriostatic water.

In the ipamorelin surgical trial, the share of patients with any treatment-emergent adverse event was 87.5% on ipamorelin and 94.8% on placebo ^[3]. Those were short hospital courses in people recovering from surgery, so they say little about repeated use in healthy people. Sermorelin’s licensed-use data describe it as well tolerated, with transient facial flushing and injection-site pain the most common complaints ^[4]; the paediatric study found no adverse changes in routine blood tests or fasting glucose ^[5].

Longer-term concerns are shared with the whole GH axis. Problems a 2026 endocrinology review attributes to the class as a whole include disturbed hormone and blood-sugar levels, fluid build-up, aching muscles and joints, and reactions at the injection site; the same review stresses that unregulated products may not contain what their labels say ^[13]. For ipamorelin that last point has a documented example: anti-doping laboratories identified glycine-extended ipamorelin in black-market products ^[18].

For diagnosing GH deficiency, sermorelin was a licensed test, used alongside other stimulation tests because a normal response cannot rule out a problem in the hypothalamus ^[4]. For growth in GH-deficient children, sermorelin has an open-label trial and a former licence, with smaller gains than daily GH ^[4][5]. For gut recovery after surgery, ipamorelin was tested and did not beat placebo on its main measure ^[3].

For the goals most people search for, such as muscle, fat loss, recovery, sleep or ageing, neither has a controlled trial in healthy adults. The closest data are sermorelin’s two small studies in older men, one of which improved two of six strength measures without changing body composition ^[7]. Ipamorelin’s bone and muscle findings come from rats. On that basis there is no evidence-based way to rank the two for these uses.

Because they act on different receptors, sermorelin and ipamorelin are a textbook candidate for combination. The rationale is a 1990 study in which healthy men received a GH-releasing hexapeptide with natural GHRH: at submaximal doses the pair released GH synergistically, more than the sum of each alone ^[10]. That study did not use either sermorelin or ipamorelin, and no published trial has given the two together.

Searches for a sermorelin ipamorelin blend show that premixed vials are sought, as they are for CJC-1295 and ipamorelin. Any ratio in such a vial is a manufacturing choice rather than a studied dose, and every draw contains both peptides in that fixed proportion.

This search compares a single GHRH analogue with a two-peptide pairing. CJC-1295 is itself built on the sermorelin sequence, with four amino-acid substitutions and, in its DAC form, an albumin-binding group; most blends use the no-DAC version, which has no human studies. Our CJC-1295 and ipamorelin page covers the pairing in detail. The short version is that no trial has compared sermorelin alone with any GHRH-plus-ipamorelin combination.

Adding tesamorelin brings in the only one of the three with a current licence and phase 3 trials, for abdominal fat in people with HIV. It is a GHRH analogue like sermorelin, so its comparison with sermorelin is about molecule and evidence rather than receptor; see tesamorelin vs sermorelin. Its comparison with ipamorelin crosses the two classes; see tesamorelin vs ipamorelin.

Ipamorelin has five amino acids and sermorelin 29, so a milligram of each is a different number of molecules and the two are not priced on the same scale. Compare ipamorelin prices and sermorelin prices per milligram. A certificate of analysis should report a mass matching the molecule on the label; our COA reading guide walks through the checks, and suppliers that publish COAs make that check possible before buying.