GLP-1 tool guide
GLP-1 dose cycle calculator: what day of my cycle am I on?
Written by Bikki Varma · Reviewed by Nishat Anjum, Dietician / Nutritionist, Phd scholar · Updated
For people already prescribed GLP-1 medication. Weight Easy does not prescribe, sell or arrange medication; your prescriber is responsible for treatment decisions.
In brief
Day 1 is your injection day. Semaglutide (Ozempic, Wegovy) peaks 1 to 3 days after the shot and tirzepatide (Mounjaro, Zepbound) peaks within about 1 day. Levels then fall until your next dose, which is why appetite is lowest early in the week and hunger often returns on days 6 and 7.
Open the free GLP-1 Dose Cycle Calculator →How the weekly GLP-1 cycle works
Once-weekly GLP-1 medicines are absorbed slowly from under the skin. The level in your body rises after each injection, peaks, then falls through the week. Because the half-life is about a week for semaglutide and about five days for tirzepatide, some medication is always left when the next dose goes in, so levels build up over the first month on a dose.
That rise and fall is why the same dose can feel different on different days. Most people notice their strongest appetite control and most side effects in the first few days after the shot, and more hunger and food noise near the end of the week.
What each day of the cycle usually feels like
Everyone responds differently, but this is the pattern most people report:
- Day 1 (shot day): level rising; nausea is most likely in the first 24 to 72 hours, especially after a dose increase.
- Days 2 and 3: near the peak; appetite is usually lowest, so small protein-first meals matter most.
- Days 4 and 5: the steady middle of the week; a good time for fuller meals and strength training.
- Days 6 and 7: level is lowest; hunger and food noise often return before the next shot.
How to use your cycle day
Knowing your cycle day turns a confusing week into a plan. Prepare gentle meals for shot day, protect protein when appetite is low, and plan snacks for the late-week dip instead of reading hunger as failure.
If symptoms appear far from the usual window, or your level chart and how you feel do not match, write it down and discuss it with your prescriber.
How this calculator estimates your level
The chart uses a standard one-compartment model with the half-life and peak time from each medicine's label, and assumes you followed the usual 4-week dose steps. It shows a relative level, not a blood concentration, and it is never used to recommend a dose.
Frequently asked questions
FAQ
Is Day 1 the day I inject?
Yes. Day 1 is your injection day, and Day 7 is the day before your next weekly shot.
When does Mounjaro peak after injection?
Tirzepatide (Mounjaro, Zepbound) reaches its highest level between 8 and 72 hours after the injection, usually within about a day. Its half-life is about 5 days.
When does Ozempic or Wegovy peak after injection?
Semaglutide (Ozempic, Wegovy) peaks 1 to 3 days after the injection and has a half-life of about 7 days, so levels fall slowly through the week.
Why am I hungrier at the end of the week on a GLP-1?
Your medication level is lowest on days 6 and 7, just before the next dose, so appetite control is weaker. This is a normal drug pattern. Protein-forward meals and planned snacks help.
Does Mounjaro wear off after 5 days?
It does not wear off, but the level keeps falling after the first day or two, so many people feel less effect from about day 5. Some tirzepatide is still active when the next weekly dose is due.
How long until my GLP-1 level is steady?
Levels build up for about 4 to 5 weeks on a stable weekly dose because each shot adds to what is left from earlier doses. The calculator shows how close you are.
Sources and limits
- Ozempic, Wegovy, Mounjaro and Zepbound prescribing information (half-life and time to peak).
- Level curve: one-compartment model with first-order absorption, relative units only.
This guide is educational, not a diagnosis, prescription or dose-change instruction. Always follow your medication leaflet and clinician.