Semaglutide Half Life: What the PK Data Says

TL;DR

The semaglutide half life is about 1 week, roughly 7 days, per FDA prescribing information, which is why the injectable form is dosed once weekly. Steady-state levels build over about 4 to 5 weeks, and after the last dose it takes roughly 5 weeks for levels to fall to near-zero. The long half-life comes from tight binding to the blood protein albumin plus a structure that resists rapid enzyme breakdown. This page reports what research and the drug label describe. It is educational, not a prescription or a personal recommendation.

What is the semaglutide half life?

The semaglutide half life is approximately 1 week, about 7 days, according to FDA prescribing information.

Half-life is the time it takes for the amount of a drug in the body to drop by half. A roughly 7-day half-life is long for a peptide, and it is the main reason the injectable form is given once per week (FDA prescribing information for Ozempic and Wegovy; semaglutide entry, Wikipedia summarizing the label). The same molecule is also sold in an oral form taken daily. That daily schedule is driven by low and variable absorption from the gut, not by a shorter half-life (FDA prescribing information).

Why does semaglutide have such a long half-life?

The long half-life comes from strong binding to the blood protein albumin plus structural changes that slow enzyme breakdown, per FDA prescribing information.

Native GLP-1, the gut hormone semaglutide is based on, is broken down within minutes by an enzyme called DPP-4 (dipeptidyl peptidase-4). Semaglutide is engineered to last far longer. A fatty acid chain attached to the peptide lets it bind tightly to albumin, which keeps it in circulation and slows how fast the kidneys remove it. A small change to the peptide backbone (an alanine swapped for aminoisobutyric acid at position 8) makes it resistant to DPP-4 breakdown. Together these features stretch its stay in the body from minutes to about a week (FDA prescribing information; semaglutide entry, Wikipedia summarizing the label).

How does the half-life explain once-weekly dosing?

A roughly 7-day half-life means about half of a dose is still present a week later, so a once-weekly schedule keeps blood levels relatively stable.

Because one half-life passes in about 7 days, roughly 50 percent of a dose remains when the next weekly dose is due. Repeated weekly dosing lets the drug accumulate to a steady level instead of spiking and crashing between doses. This is the pharmacokinetic logic behind the once-weekly injectable schedule (FDA prescribing information).

How long until semaglutide reaches steady state?

FDA prescribing information reports that steady state is reached after about 4 to 5 weeks of once-weekly dosing.

A drug reaches steady state after about 5 half-lives. With a half-life near 7 days, that math lands at roughly 4 to 5 weeks. This is why the appetite and weight effects reported in trials build over time rather than appearing after a single dose. In STEP 1, mean weight loss reached about 15 percent only after 68 weeks of treatment (Wilding et al., NEJM 2021; PMID 33567185), and published research describes GLP-1 weight loss slowing toward a plateau over many months, with continued treatment needed to sustain it (weight regain data, Wilding et al., Diabetes Obesity and Metabolism 2022; PMC9542252).

How long does semaglutide stay in your system after stopping?

With a half-life of about 1 week, semaglutide takes roughly 5 weeks to fall to near-zero after the last dose, based on standard pharmacokinetics.

Clearing a drug takes about 5 half-lives, and each half-life here is close to 7 days, so semaglutide is largely gone about 35 days after the final dose. Levels do not crash overnight, so any changes fade gradually. Trial data also show much of the lost weight can return after stopping: the STEP 1 extension reported participants regained about two-thirds of their lost weight in the year after treatment ended (Wilding et al., Diabetes Obesity and Metabolism 2022; PMC9542252).

What does research report on semaglutide dosing?

The ranges below reflect what published studies and commonly studied research protocols report. This is educational, not a prescription or a personal recommendation.

### Semaglutide pharmacokinetics at a glance

### Illustrative single-dose decay

Illustrative single-dose decay using a 7-day half-life. Real blood levels differ with repeated weekly dosing and individual factors. This is arithmetic for reference, not a dosing instruction.