Ipamorelin vs Sermorelin: Dosing & Units Compared

Ipamorelin and sermorelin are both injectable peptides used to raise growth hormone (GH), but they are not two versions of the same thing: sermorelin is a growth hormone–releasing hormone (GHRH) analog that tells the pituitary to make more GH, while ipamorelin is a ghrelin/growth hormone secretagogue receptor (GHS-R) agonist that triggers a GH pulse. Because they act on different receptors, they are more often combined than swapped one for the other — and whichever you draw, both are dosed in micrograms and reconstituted from freeze-dried powder using the exact same arithmetic.

TL;DR — key takeaways

• Different receptors. Sermorelin binds the GHRH receptor; ipamorelin binds the ghrelin/GHS-R1a receptor. Their signals converge on the same somatotroph cells but through separate pathways.
• Both dosed in micrograms. Typical research and clinic protocols land in the low hundreds of mcg per injection — far smaller numbers than the milligram GLP-1 world, so unit math matters even more.
• Units follow concentration, not the peptide. The number of syringe units you draw depends on how much BAC water you added to the vial, not on whether it says “ipamorelin” or “sermorelin” on the label.
• Investigational status differs. Sermorelin was once FDA-approved (Geref, now discontinued in the US); ipamorelin has never been FDA-approved and remains a research compound. Neither is a general-use drug — this page is math, not medical advice.

Two receptors, two different jobs

Sermorelin is a 29–amino acid fragment of natural GHRH — the first 29 residues, which is the smallest piece that keeps full activity. It works “upstream”: it binds the GHRH receptor on pituitary somatotrophs, raises intracellular cyclic AMP, and increases the synthesis and release of the body’s own growth hormone. Because it pushes a natural feedback loop rather than injecting GH directly, the pituitary still governs how much is released, which is the physiological argument reviewers have made in its favor.

Ipamorelin is a synthetic pentapeptide (five amino acids) that mimics ghrelin at the GHS-R1a receptor. Instead of nudging GH synthesis, it drives a sharp, short GH pulse. Its defining feature, established in the original 1998 characterization, is selectivity: unlike earlier GH-releasing peptides such as GHRP-2 and GHRP-6, ipamorelin released GH without meaningfully raising cortisol, ACTH, or prolactin. That clean profile is why it is frequently chosen for GHS-R–side dosing.

Because one arm is GHRH-like and the other is ghrelin-like, the two are complementary. A GHRH analog primes the cell while a GHS-R agonist releases the pulse, and co-administration has been shown to amplify GH output beyond either alone. That is the mechanistic reason you far more often see sermorelin or a longer GHRH analog paired with ipamorelin than pitted against it.

Side-by-side: how they compare

Half-life figures reflect the published pharmacology and are short for both, which is why protocols commonly split injections across the day and time them away from meals; the numbers above are for orientation, not a prescription.

The dosing math is identical for both

Here is the part people actually get stuck on. Both peptides ship as a lyophilized (freeze-dried) powder measured in milligrams, and both are dosed in micrograms. The syringe, however, reads in units — a U-100 insulin syringe has 100 units per 1 mL. So the conversion is always the same three steps, and it does not care which peptide is in the vial:

• Concentration = powder amount ÷ BAC water added (gives mg/mL, then ×1000 for mcg/mL).
• Volume = your dose (mcg) ÷ concentration (mcg/mL).
• Units = volume (mL) × 100.

The diagram below shows why the same 300 mcg dose can sit at two completely different marks on the same syringe — the only thing that moved was how much water went into the vial.

Worked examples — the numbers

Dose-to-units reference chart

Common microgram doses shown as units on a U-100 syringe at two typical reconstitution concentrations. Always confirm against your own vial label and your prescriber’s dose.

Notice the whole chart shifts if you change the water: the “units” column is a property of the vial, not the peptide. This is exactly what trips people up when they follow someone else’s “draw 15 units” advice without checking the concentration behind it.

How this is calculated

Every number on this page comes from two facts and nothing else: a U-100 syringe holds 100 units per mL, and concentration is simply the powder amount divided by the volume of BAC water you add. There is no peptide-specific constant — the arithmetic for sermorelin, ipamorelin, or any other vialled peptide is the same. We do not review or recommend doses; the worked examples use round, illustrative figures so you can follow the method and then check your own vial against the tool. This is an education and math resource, not medical advice, and neither peptide is a general-use approved medicine — use only under appropriate professional supervision.

Frequently asked questions