"Sermorelin vs ipamorelin" is usually asked as if the two were interchangeable ways of raising growth hormone. The sources say otherwise: they bind different receptors, one lasts minutes in the blood and the other hours, one was an approved drug and the other never was, and the same microgram figure is a different number of molecules. This page sets the two side by side and reports what each source states. It compares compounds; it recommends neither.
Taking the two together is a different question, covered on the sermorelin and ipamorelin stack page. Each compound's full dosage record is on its own page: sermorelin and ipamorelin. Medibact's guides cover the compounds themselves: Sermorelin and Ipamorelin.
Side by side
| Sermorelin | Ipamorelin | |
|---|---|---|
| What it is | GHRH(1-29), the first 29 residues of growth-hormone-releasing hormone | A synthetic five-residue secretagogue |
| Formula, molecular weight | C149H246N44O42S, 3,357.9 | C38H49N9O5, 711.9 |
| Receptor | GHRH receptor | Ghrelin (GH secretagogue) receptor |
| Measured half-life | 4.3 min (IV infusion, 10 men) | 2 hours terminal (IV, healthy men) |
| Approved product | Geref, NDA 020443, 1997; discontinued, withdrawal not for safety or effectiveness (FDA, 2013) | Never approved |
| Labelled or trial regimen | 30 mcg/kg once daily at bedtime, children with GH deficiency | 0.03 mg/kg IV twice daily for 7 days after bowel surgery |
| ClinicalTrials.gov intervention records | 27 | 3 |
| PubMed title/abstract records | 24 | 50 |
| FDA 503A Category 2 (Sept 2023) | Not listed | Listed |
Sources: PubChem CIDs 16132413 and 9831659; Soule et al. 1994 (PMID 7962295); Gobburu et al. 1999 (PMID 10496658); Prakash and Goa 1999 (PMID 18031173); Raun et al. 1998 (PMID 9849822); Thorner et al. 1996 (PMID 8772599); Beck et al. 2014; the registry and PubMed counts were read on 2026-09-24. The approval history and the Category 2 listing are as recorded, with their sources, on the sermorelin and ipamorelin dosage pages.
Two receptors, two kinds of signal
Growth hormone is released under two separate inputs. Sermorelin copies the hypothalamic releasing hormone, and the 1999 review of it describes GHRH(1-29) as the shortest fragment that keeps the full activity of the natural 44-residue hormone. Ipamorelin is not a fragment of either hormone: it was built at Novo Nordisk to act at the ghrelin receptor, and the 1998 paper that introduced it reported growth-hormone release with no cortisol or ACTH release, which is what "selective" referred to. That separation of receptors is the pharmacological reason the two are so often combined, and the reason a figure for one says nothing about the other.
Minutes against hours
The half-life gap is the largest single difference in the table. A 1994 infusion study measured GHRH(1-29)-NH2 disappearing from the blood with a half-time of 4.3 minutes, and a D-Ala2 variant with 6.7 minutes; ipamorelin's intravenous study found a terminal half-life of 2 hours and a single growth-hormone peak at about 40 minutes. Two hours against 4.3 minutes is roughly a thirtyfold difference (this site's arithmetic). Both figures are intravenous and neither describes an injection under the skin, where absorption stretches the curve; no subcutaneous half-life study was found for either compound. The tesamorelin vs sermorelin page shows that a longer GHRH analogue changes this picture only by minutes.
Equal micrograms, unequal doses
Vendor pages state both compounds in the same range, a few hundred micrograms, which invites reading them as equivalent. By molecule count they are not. At the PubChem weights, 250 mcg of sermorelin is about 74 nanomoles and 250 mcg of ipamorelin about 351 nanomoles, so an equal microgram figure delivers about 4.7 times as many ipamorelin molecules. The paediatric sermorelin regimen, 30 mcg/kg, is about 8.9 nmol/kg; ipamorelin's intravenous study ran from 4.21 to 140.45 nmol/kg. Because the two act at different receptors with different potencies, even equal nanomoles would not be equal effects. The comparison shows only that the microgram figure is the wrong unit for comparing them.
The figures each source states
| Source grade | Sermorelin | Ipamorelin |
|---|---|---|
| Label | 30 mcg/kg once daily at bedtime (children, GH deficiency); 1 mcg/kg IV as a diagnostic test | None |
| Trial | Thorner 1996: 30 mcg/kg SC nightly, 110 children, up to a year | Beck 2014: 0.03 mg/kg IV twice daily, 114 patients after bowel resection, no significant difference from placebo on the main endpoint |
| Clinic and vendor pages (surveyed 2026-09-18) | 200 to 500 mcg SC nightly, often 200 to 300 mcg to start | 100 to 300 mcg SC, one to three times daily |
The third row is a market convention in both columns, without a trial behind it; the sermorelin and ipamorelin dosage pages record the pages surveyed. For a 70 kg adult the labelled 30 mcg/kg would be 2.1 mg of sermorelin, and ipamorelin's trial 0.03 mg/kg would be 2.1 mg intravenously; both are several times the vendor figures, and neither was set for adults using the compound under the skin.
The arithmetic per vial
Research vials of both are commonly labelled 5 mg and 10 mg. Units on a U-100 syringe = mcg ÷ (mcg per mL) × 100.
| Amount | 5 mg + 2 mL (2.5 mg/mL) | 5 mg + 1 mL (5 mg/mL) | 10 mg + 2 mL (5 mg/mL) |
|---|---|---|---|
| 100 mcg | 4 units | 2 units | 2 units |
| 200 mcg | 8 units | 4 units | 4 units |
| 300 mcg | 12 units | 6 units | 6 units |
| 500 mcg | 20 units | 10 units | 10 units |
The table is identical for both compounds, which is the point: the syringe measures volume and the concentration measures mass, and neither sees the molecule. The sermorelin calculator preset and the ipamorelin preset work other vial sizes, and the reconstitution pages for sermorelin and ipamorelin set out each vial.
What is not established
No trial has compared sermorelin with ipamorelin. No trial has given either to adults under the skin at the vendor-stated amounts for body composition, sleep or recovery. Neither half-life has been measured after a subcutaneous injection. Which compound, if either, suits anyone is a decision for a prescriber, and this page reports sources, not a choice.
Sources and dates
Opened 2026-09-24: PubChem compound records 16132413 (sermorelin) and 9831659 (ipamorelin); PubMed abstracts of Soule S et al., J Clin Endocrinol Metab 1994;79:1208-11 (PMID 7962295) and Gobburu JV et al., Pharm Res 1999;16:1412-6 (PMID 10496658); PubMed counts for sermorelin[tiab], ipamorelin[tiab] and both together (5), with a metformin control; ClinicalTrials.gov v2 intervention counts. Carried from this site's sermorelin and ipamorelin pages (sources opened 2026-09-18 and listed there): Prakash and Goa 1999, Raun et al. 1998, Thorner et al. 1996, Beck et al. 2014, Drugs@FDA NDA 020443, the FDA Federal Register determination of 2013-03-04, the 503A Category 2 listing and the vendor survey. Molecule and unit arithmetic by this site. Corrections go to the contact page.