Half-life
Clinical reviewer: Jacob Moore, MD · Last checked September 24, 2026
What is a drug half-life?
Half-life is the time it takes for the amount of a drug in the body to fall by half. Semaglutide, in Wegovy and Ozempic, has a half-life of approximately 1 week. Tirzepatide, in Zepbound, has an elimination half-life of approximately 5 to 6 days. Both are dosed once weekly.
How long are the half-lives of semaglutide and tirzepatide?
Wegovy's label describes "the long half-life of WEGOVY of approximately 1 week" when discussing overdose observation [2]. Zepbound's label states "the elimination half-life is approximately 5-6 days in patients with overweight or obesity," and Mounjaro's label describes tirzepatide's half-life as "approximately 5 days, enabling once-weekly dosing" [3][4]. StatPearls defines elimination half-life as the time required for a drug's concentration to decrease by half [1].
What practical effects does a long half-life have?
Wegovy's label says to discontinue it at least 2 months before a planned pregnancy "because of the long half-life of semaglutide" [2]. Tirzepatide's long half-life comes partly from a C20 fatty diacid that enables albumin binding, according to Zepbound's label, and steady-state tirzepatide concentrations are reached after 4 weeks of once-weekly dosing per the Mounjaro and Zepbound labels [3][4].
Frequently asked questions
Why do labels mention half-life for pregnancy planning?+−
Wegovy's label says to stop the drug at least 2 months before a planned pregnancy because of semaglutide's long half-life.
What makes tirzepatide's half-life so long?+−
Zepbound's label attributes it partly to a C20 fatty diacid that enables albumin binding and prolongs the half-life.
Related terms
Sources
This entry is for education and is not medical advice. Talk with a licensed clinician about your own situation before starting, stopping, or changing any treatment.
