If you've missed a Mounjaro dose, what to do depends on how late you are. If it has been 4 days or less since the dose was due, inject it as soon as you remember and take your next dose on your usual day; if more than 4 days have passed, skip it and simply inject on your next usual day. Never take a double dose to make up for a missed one.
That's the rule in the UK patient leaflet for Mounjaro KwikPen (last revised August 2026) and the Summary of Product Characteristics (SmPC), and the NHS tirzepatide page agrees, as of September 2026. Mounjaro (tirzepatide) is a prescription-only medicine, and a prescriber decides whether it's suitable for you. This article is information only, not medical advice: the leaflet in your own pack, your prescriber and your pharmacist come first.
Missed a Mounjaro dose? What to do, by how late you are
Count from the day and rough time you normally inject, then follow the matching step:
- 4 days or less late: inject the missed dose as soon as you remember. Then inject your next dose as usual on your scheduled day.
- More than 4 days late: skip the missed dose. Then inject your next dose as usual on your scheduled day.
- Not sure how late you are: don't guess. Ask your pharmacist or prescriber before you inject.
How do I count the 4 days?
Say you normally inject on a Sunday morning:
- You remember on Monday, Tuesday or Wednesday: inject that day, then again on Sunday as normal.
- You remember on Thursday: you're right on the 4-day line. If it's still earlier than your usual injection time, inject; if it's later, skip it. The US prescribing information gives the same window as 96 hours. If you're unsure, ask your pharmacist.
- You remember on Friday or Saturday: more than 4 days have passed, so skip it and inject on Sunday as planned.
The two rules fit together. The leaflet says the minimum time between two doses must be at least 3 days, and a dose given no more than 4 days late still leaves at least 3 days before your next scheduled injection.
Why can't I take two doses to catch up?
The leaflet is plain about it: do not use a double dose to make up for a forgotten dose. Tirzepatide is long-acting. The SmPC gives its half-life as approximately 5 days, so the amount in your body falls only slowly between injections, and it notes that an overdose may need a prolonged period of observation and treatment. According to the leaflet, too much Mounjaro may cause low blood sugar (hypoglycaemia) and can make you feel sick or be sick.
If you've injected twice by mistake
If you've used more than your prescribed dose, the leaflet says to talk to your doctor immediately, and the NHS advises getting help from NHS 111, by phone or online. If you're told to go to A&E, don't drive: ask someone to drive you or call 999, and take the pack or leaflet and any remaining medicine with you.
Can I change my injection day instead?
Yes. If your usual day keeps slipping, the leaflet allows you to change the day of your weekly injection, as long as it has been at least 3 days since your last injection. After choosing the new day, carry on injecting once a week on that day. You can inject at any time of day, with or without meals. Our dosage page explains the weekly schedule and the step-up in full.
What if I've missed more than one dose?
As of September 2026, the UK leaflet, the SmPC and the NHS tirzepatide page don't give a separate rule for missing two or more doses in a row, or for a break of several weeks. In that situation:
- Speak to your prescriber or pharmacist before your next injection. Tell them how many doses you've missed and which strength you were on.
- Don't change your dose yourself. The leaflet says not to change your dose unless your doctor has told you to, so let your prescriber decide which strength you restart on.
- Check your contraception. If you take the pill and your dose is stepped up again, the leaflet says to consider also using a barrier method such as a condom, or switching to a non-oral method, for 4 weeks after each dose increase.
Don't stop altogether without talking to your doctor. And if doses were missed because your pens ran out, arrange your next supply through your prescriber: never buy tirzepatide from an unregulated seller or use a "compounded" version.
What happens to my pen if I skip a dose?
Each KwikPen holds 4 doses. Unused pens are kept in the fridge at 2°C to 8°C and must not be frozen. The SmPC says that after first use a pen may be stored unrefrigerated at up to 30°C for up to 30 days, and then it must be discarded. The 30 days count from first use, even if the pen goes back in the fridge.
Skipping one dose still lets you finish a pen within 30 days of first using it, but skip two from the same pen and its last dose would fall after that. Note the date you start each pen, and ask your pharmacist or prescriber about your next supply if skipped doses leave a pen near its 30-day mark. Our guide to using and storing the pen has more on the 30-day rule.
What if I feel unwell around a late dose?
The leaflet notes that, when starting treatment, vomiting, feeling sick or diarrhoea can sometimes cause dehydration, which may reduce kidney function, so drink plenty of fluids. Stop using Mounjaro and get urgent medical help for severe stomach pain that won't go away, with or without feeling or being sick: it could be a sign of an inflamed pancreas (acute pancreatitis). You can report any suspected side effect through the MHRA Yellow Card scheme, and our side effects page covers what to expect.
How can I stop missing doses?
- Mark your day. The leaflet suggests ticking the day of the week of your first dose on the Instructions for Use, or marking it on a calendar.
- Set a repeating phone reminder for your injection day, plus a backup the next morning, well inside the 4-day window.
- Keep a simple log of the date, strength and injection site. It shows at a glance whether a dose was given and helps with rotating injection sites.
- Pack it for trips. A pen you've started can be kept out of the fridge at up to 30°C within its 30 days, so it can come with you.
New to the pen? Our first-time injection guide walks through each step, and our general FAQ covers wider questions.
Frequently asked questions
Can I take Mounjaro a day or two late?
Yes. If it's 4 days or less since your dose was due, inject as soon as you remember, then take your next dose on your usual day.
Is it OK to skip a week of Mounjaro?
If more than 4 days have passed, the leaflet says to skip the missed dose and inject your next one as usual on your scheduled day. Don't skip doses on purpose or stop without talking to your doctor, and if you've missed more than one dose in a row, speak to your prescriber or pharmacist before injecting again.
Should I take a double dose to catch up?
No. The leaflet says not to use a double dose to make up for a forgotten one, and doses must be at least 3 days apart. If you've injected more than your prescribed dose, talk to your doctor straight away or contact NHS 111.
What if I've missed two or more doses in a row?
As of September 2026, the UK leaflet doesn't give a rule for this. Contact your prescriber or pharmacist before your next injection, and don't change your dose unless your prescriber tells you to.
Can I change my Mounjaro injection day?
Yes, as long as it has been at least 3 days since your last injection. Then carry on once a week on the new day, at any time of day, with or without meals.