Semaglutide vs Tirzepatide: what is the difference?

Semaglutide acts at one receptor, tirzepatide at two. Semaglutide is 31 amino acids built on human GLP-1; tirzepatide is 39 built on GIP. Both carry a fatty diacid that binds albumin and stretches their half-life in research models. On a lab report they are 700 daltons apart.

One receptor or two

Semaglutide is a GLP-1 receptor agonist. Its sequence is human GLP-1(7-37) with two substitutions: an Aib at position 8 that resists the DPP-4 enzyme, and a lysine at 26 that carries the fatty chain. It was designed to do one thing at one receptor for a long time.

Tirzepatide starts from the GIP sequence and is engineered so that the same 39-residue chain binds both the GIP receptor and the GLP-1 receptor. It is described in the literature as a dual agonist, or an unbalanced one, because its affinity for the two receptors is not equal. The retatrutide comparison takes the idea one receptor further.

The fatty chain is the same trick, different length

Both peptides are acylated. A lysine side chain carries a linker, and the linker carries a fatty diacid: C18 for semaglutide, C20 for tirzepatide. The diacid binds serum albumin in research models, which keeps the peptide circulating instead of being cleared in minutes. Neither would be a long-acting molecule without it.

The chain is also why both are harder to dissolve than a short peptide. Give the powder time, keep the diluent running down the glass, and do not shake.

700 daltons apart on the mass spec

The identity check on a lab report compares the observed mass to the expected one. A semaglutide vial should read near 4113.6; a tirzepatide vial near 4813.5. The gap is large enough that a mislabelled vial fails the check outright rather than sitting in a grey zone. How to read a peptide lab report shows where that number sits on the certificate.

Vial sizes and the molar difference

A 10 mg vial of semaglutide holds 2.43 micromoles. A 10 mg vial of tirzepatide holds 2.08 micromoles, because each molecule is heavier. If your work is in molar units the two are not interchangeable at the same mass, and the calculator does the conversion for either: semaglutide or tirzepatide.

Storage is the same

Lyophilized, both keep in a freezer for the long term and a fridge for the short. Reconstituted, both belong in the fridge and should not be frozen. The acyl chain does not change the storage rules; how to store research peptides applies to both without exception.

In one line

Semaglutide is the single-receptor GLP-1 analog at 4113.58 g/mol. Tirzepatide is the dual GIP and GLP-1 agonist at 4813.45 g/mol. Both ship from pepuro in every size we list, free, with the report on the vial.

For research use only. Not for human or animal consumption.