Glossary
Half-Life
Half-life is how long a concentration takes to fall by half. Peptide values range from two minutes to a week — and shelf stability is a different matter.
Half-life (t½) is the time it takes for a concentration to drop to half of its initial level. With first-order elimination, the same fraction is removed in every time interval, so about 97% of a compound is gone after five half-lives, whatever amount you started with. Published figures are generally terminal half-lives, read from the last log-linear part of the concentration curve, and they belong to a particular species and route rather than to the molecule as such.
An extreme range in peptides
Peptides cover an exceptionally broad spectrum. DPP-4 breaks down native GLP-1 in roughly two minutes, whereas the licensed medicine semaglutide, fitted with a fatty-acid chain that binds albumin, shows a reported human half-life of close to one week. Structural engineering thus yields a difference of about five-thousand-fold — the very reason approaches like DAC and PEGylation were developed.
Keep two frequent misunderstandings apart. Plasma half-life concerns removal from the bloodstream; it says nothing about how long a reconstituted vial lasts in the fridge, which depends on hydrolysis and oxidation. And a long half-life does not guarantee a long period of measurable effect, because receptor occupancy and downstream signalling run on their own timescales. More background is in the stability and half-life guide.
Related terms
bioavailability · GLP-1 peptides collection