GLP-1 half-life: why the days before your next shot can feel different
Semaglutide’s half-life is about a week, tirzepatide’s about 5 days. What that means for the level of medication between shots, explained simply.
By the Steady team ·
A half-life is how long it takes the body to clear half of a medication. It is why a weekly GLP-1 can be taken once a week at all, and it is why the amount in your body is not flat between shots: it rises after a dose and falls slowly until the next one.
Half-lives from the labels
| Ingredient | Brands | Half-life (label) | Usual schedule |
|---|---|---|---|
| Semaglutide | Ozempic, Wegovy, Rybelsus | About 1 week | Weekly injection, or daily tablet |
| Tirzepatide | Mounjaro, Zepbound | About 5 days | Weekly injection |
| Dulaglutide | Trulicity | About 5 days | Weekly injection |
| Liraglutide | Saxenda, Victoza | About 13 hours | Daily injection |
What happens between two weekly shots
After a weekly injection the level climbs for a day or more, then declines through the week. With a half-life close to the dosing interval, the next shot arrives while a good share of the last one is still there, and after several weeks on the same dose the ups and downs settle into a steady pattern.
Some people say they notice their appetite coming back toward the end of the week. Whether that happens, and how much, varies from person to person. If it bothers you, it is worth raising with your prescriber rather than moving your shot day on your own.
How Steady draws your curve
Steady takes the dose and date you log and your medication’s published average pharmacokinetics, and draws an estimated level curve: where you are now, where the low point is and when the next dose is due. It updates when you log a dose or change dose.
It is an estimate from averages, not a blood test. Steady cannot measure the medication in your body, and it never suggests changing a dose.
- Ozempic® (semaglutide) · Injection, once a week
- Wegovy® (semaglutide) · Injection, once a week
- Mounjaro® (tirzepatide) · Injection, once a week
- Zepbound® (tirzepatide) · Injection, once a week
Sources
- Ozempic prescribing information (DailyMed)
- Mounjaro prescribing information (DailyMed)
- Trulicity prescribing information (DailyMed)
- Victoza prescribing information (DailyMed)
This guide is general information from product labels and public sources. It is not medical advice. Follow your prescriber’s instructions and your medication’s label, and ask your doctor or pharmacist about anything specific to you.
Questions
How long does semaglutide stay in your system?
Its half-life is about a week, so most of a dose is cleared after about five weeks.
How long does tirzepatide stay in your system?
About 5 days of half-life, so three to four weeks for most of a dose to clear.
What does half-life mean?
The time it takes the body to clear half of the medication.
Does a long half-life affect switching medications?
It can, which is one reason your prescriber plans the timing of a switch.
Why do some people feel hungrier before their next shot?
Some report it, as the level falls toward its low point. It varies; raise it with your prescriber rather than moving your shot day yourself.
Can I see my own level curve?
Yes. The level graph on this site shows an estimate for any medication and dose, and Steady draws yours from your logged doses.
Is Steady medical advice?
No. Steady records what you log and does arithmetic on it. It does not diagnose, prescribe or recommend a dose, and it is not a substitute for your prescriber or pharmacist.
Is Steady on iPhone and Android?
Yes. Steady is on the App Store for iPhone and on Google Play for Android.
Do I need a subscription?
Yes. Tracking, reminders, the level estimate and the widgets come with Steady Pro. Plans are on the pricing page, and you can cancel any time.