What’s behind it
The half-life tells you how long it takes for half of the active substance to be broken down. For tirzepatide that is around 5 days. This means: shortly before the next weekly injection there is considerably less active substance in the blood than one or two days after it. After about four weeks on the same dose a steady state is reached – but the fluctuation remains.
On top of that: if you stay on the same dose for longer, you partly get used to the effect, especially to the feeling of fullness.
What helps in everyday life
- A fixed day of the week and, if possible, the same time
- Plan the “weak” days deliberately: prepare protein-rich meals, keep snacks out of reach
- Drink plenty – thirst is often mistaken for hunger
- Note down which days are difficult – in the Tracker or simply on paper. That helps when you talk to your doctor.
What you shouldn’t do
- Increase the dose or shorten the interval on your own
- Combine additional substances to fill the gap – the interactions, especially on the gut and blood sugar, have not been studied
Bring up the weak days with your doctor. Whether a dose adjustment makes sense can only be decided there.
When to see a doctor
- The effect noticeably wears off over weeks
- You are thinking about changing the dose or interval or adding other substances
In an emergency: call 112.
FAQ
Why am I hungry again on day 6?
Because the level of the active substance is lowest at the end of the weekly interval. Tirzepatide has a half-life of about 5 days.
Can I inject Mounjaro more often than once a week?
Mounjaro is approved for once-weekly use. Only make changes after consulting your doctor.
Is it normal for the effect to wear off over time?
Partial habituation, especially to the feeling of fullness, is often reported. Whether the dose should be adjusted is for your doctor to decide.
Sources
This article does not replace medical advice. It does not give any dosing recommendations. As of September 2026.