If you are on a weekly GLP-1 like Wegovy, Ozempic, Zepbound or Mounjaro, you may know this pattern: the first days after your shot, food is quiet. By day 5 or 6, the snack thoughts are back. It is one of the most common things people describe, and there is a simple piece of pharmacology behind part of it.
Your medication level moves through the week
A weekly shot does not put a steady amount of medication in your body. After the injection, the medication is absorbed over a day or two and reaches its highest level. Then your body clears a little of it every day until the next shot.
How fast it clears depends on the half-life, the time it takes for the amount to drop by half:
- Semaglutide (Wegovy, Ozempic): about 7 days
- Tirzepatide (Zepbound, Mounjaro): about 5 days
So the day before your next shot is the low point of your week. With tirzepatide, the shorter half-life means a bigger gap between the high and low days than with semaglutide.
What the curve looks like
Here is what a simple model based on the published half-life and absorption shows, once your dose has settled. Each number is the estimated level that day, as a share of your weekly peak.
| Day after the shot | Semaglutide | Tirzepatide |
|---|---|---|
| Day 1 | 99% | 95% |
| Day 3 | 83% | 73% |
| Day 5 | 68% | 55% |
| Day 6 | 62% | 48% |
These are estimates from a model, not blood tests, and real levels vary from person to person. But the shape is the point: day 6 really is a different day from day 2.
The level is only part of the story
It is tempting to blame everything on the curve. Other things change through a week too:
- Routine. Many people take their shot early in the week, so the low days land on the weekend, with its dinners out and looser schedule.
- Sleep and stress. Both affect appetite on any medication or none.
- Your cycle. Hormonal changes before a period can raise appetite, whatever day of your shot it is.
- Being early on a dose. In your first weeks on a new dose, the level is still building, so the whole week sits lower.
What you can do with this
- Notice your own pattern. Rate your food noise once a day for two or three weeks. You may find it is day 6 and 7 for you, or you may find it is Saturdays whatever the shot day.
- Plan around the low days. Some people keep easy, protein-rich food ready for the end of their week, or plan social meals earlier in it.
- Talk to your prescriber. If the end of the week is hard, that is useful information for them. Your dose and schedule are their decision.
Do not move your shot earlier on your own to “fix” the hungry days. The prescribing information has specific rules for changing your shot day.
See your own week
The free GLP-1 level estimator draws your week from your medication and shot day. If you want to pick a shot day around the days that matter to you, the shot day planner lines up every option with your week.