Mounjaro (tirzepatide) is taken once a week, so it's easy to lose track of which day you're on. The good news is the manufacturer's instructions give a clear, simple rule for a missed dose — and it leaves a generous window.
The 4-day rule
According to the Summary of Product Characteristics, if you miss a dose you should take it as soon as possible **within 4 days (96 hours)** of the missed dose. If **more than 4 days** have passed, skip the missed dose entirely and take your next dose on your regular scheduled day.
The one thing never to do is take two doses close together to 'catch up' — doubling up raises the risk of side effects like nausea and vomiting without any benefit.
- Missed by 4 days or less: take it as soon as you remember, then carry on as normal.
- Missed by more than 4 days: skip it and resume on your usual day.
- Never take two doses within a few days of each other.
Shifting your dose day
If a missed dose has knocked your schedule out, you can move your regular injection day. NHS guidance notes you can change the day you take it as long as you keep at least 3 days between doses. Once you've taken the late dose, pick a new weekly day that works.
If you click-count partial doses, the clicks calculator and pen tracker help you keep your remaining doses straight after a disruption.