Restarting Mounjaro after a break: which dose to go back to

In short

A missed dose can be taken up to 4 days (96 hours) late. After that, skip it and take the next dose on your usual day
Never take two doses within 3 days of each other
The SmPC has no restart rule for breaks longer than one missed dose. The restart dose is a prescriber decision
Tirzepatide has a half-life of about 5 days, so after 3 weeks only a small fraction remains
After a gap of more than 2 weeks, most prescribers restart at a lower dose
Each dose increase after a restart needs at least 4 weeks on the current dose

The dose you restart on depends on how long you have gone without Mounjaro. If you are within 4 days (96 hours) of a missed dose, take it and carry on as normal. For anything longer, the SmPC gives no restart rule, so your prescriber decides. After a gap of more than 2 weeks most prescribers restart lower, and after a month or more many go back to 2.5mg or 5mg. Restarting too high is the most common reason people are sick after a break.

What the SmPC says, and where it stops

The Summary of Product Characteristics (SmPC) covers one missed dose. If a dose is missed, take it as soon as possible within 4 days. If more than 4 days have passed, skip it and take the next dose on your usual day. Two doses must be at least 3 days apart. You can also move your weekly injection day, as long as this gap is kept.

The SmPC does not say what to do after two, three or more missed weeks. This gap in the guidance is why you will hear different advice from different prescribers. The table below reflects common practice. Treat it as a basis for a conversation, not a rule to follow without advice.

Restart doses by length of break

Time since your last dose	Usual approach
Under 11 days (one dose up to 4 days late)	Take the missed dose and carry on at the same strength
1 dose skipped (about 2 weeks since last injection)	Most people restart at the same dose
More than 2 weeks	Most prescribers restart one step lower, sometimes two
4 weeks or more	Many prescribers restart at 2.5mg or 5mg
Several months	Treat as a new start, usually at 2.5mg

After restarting, step up again in the normal way. The SmPC sets at least 4 weeks on each dose before moving up by 2.5mg. You may move faster back to your old dose than the first time round if you tolerate each step well, but each step still needs its 4 weeks. The dose steps guide sets out the full schedule.

Why tolerance fades during a break

The first weeks on Mounjaro are hard on the stomach for many people. Tirzepatide slows how fast your stomach empties, which is part of why you feel full, and the gut adapts to this over several weeks. Starting at 2.5mg and moving up in small steps gives it time.

Tirzepatide has a half-life of about 5 days, according to the SmPC. Each 5 days, the amount in your body roughly halves. After 2 weeks without a dose, around a seventh of your usual level remains. After 3 weeks, the figure is closer to a twentieth. By this point your gut has lost much of its adjustment.

If you then inject 10mg or 15mg, your body gets a large dose with little tolerance. The result is often what people describe after a holiday break: strong nausea, vomiting, stomach pain and diarrhoea for several days. Heavy vomiting and diarrhoea can lead to dehydration, and the SmPC warns this can affect your kidneys. The page on nausea and vomiting explains how to manage it.

What to tell your prescriber before restarting

Your prescriber will want to know:

the date of your last injection and the strength
the highest dose you reached and how well you tolerated it
why you stopped, for example supply, cost, illness, surgery or side effects
any new medicines or health problems since your last dose
your current weight, for a fresh BMI check
whether you are pregnant, breastfeeding or planning a pregnancy

If you stopped because of suspected pancreatitis, do not restart without medical advice. The SmPC says tirzepatide should not be restarted if pancreatitis is confirmed. If you have type 2 diabetes and take insulin or a sulphonylurea such as gliclazide, your diabetes team may need to adjust these when you restart.

Pens and storage when you restart

Each KwikPen gives 4 fixed doses of one strength. If you restart on a lower dose, you need a new pen at the lower strength. Do not try to take part of a higher-strength dose.

Check any pen you kept during the break. An unopened pen should stay in the fridge at 2C to 8C until you start it. Once opened, the patient leaflet allows up to 30 days out of the fridge at not above 30C, after which you throw the pen away even if doses remain. A pen frozen, overheated or past its expiry date is not safe to use.

Planning a break in advance

Some breaks are unavoidable. Planning ahead with your prescriber makes the restart easier.

Surgery and anaesthesia

Mounjaro slows stomach emptying, which matters if you need a general anaesthetic or sedation. Tell your surgical team you take it, well before the operation date. They will advise whether to pause and for how long. The page on Mounjaro before surgery and anaesthesia covers what to ask.

Pregnancy

Do not use Mounjaro during pregnancy. The SmPC says to stop at least 1 month before a planned pregnancy because of the long half-life. If you become pregnant while taking it, stop and speak to your GP or midwife. The pregnancy page has more detail.

Supply gaps and pharmacy changes

If your strength is out of stock, a short gap often fits inside the 4-day window. Longer gaps follow the table above. The guide to Mounjaro supply and shortages explains what to do. If you move pharmacy during a break, your new prescriber needs the date of your last dose, covered in the guide to switching pharmacy.

Holidays and cost breaks

A holiday need not mean a break. You can move your injection day as long as two doses are at least 3 days apart, and opened pens keep for 30 days at not above 30C. If you pause to save money, expect your appetite to come back within a week or two.

Weight and appetite during a break

Hunger usually returns within 1 to 2 weeks of the last dose as levels fall. Some weight regain during a long break is common. In SURMOUNT-4, published in JAMA in 2024, people switched to placebo after 36 weeks regained an average of 14% of their body weight over the following year. Those who stayed on tirzepatide lost a further 5.5%.

A short break has a much smaller effect, especially if you keep up the habits you built on treatment. Regular meals, protein at each meal and limiting alcohol all help while the medicine is out of your system. The NHS advice is to talk to your doctor before stopping tirzepatide.

Questions people ask

Can I go straight back to my old Mounjaro dose after a break?

After a gap of up to about 2 weeks, many prescribers let you restart on your previous dose. After more than 2 weeks, most restart you lower, because your gut has lost its tolerance. Going straight back to a high dose after a long gap often causes severe nausea and vomiting.

I missed one Mounjaro dose. Do I need to restart at 2.5mg?

No. If you are within 4 days (96 hours) of your usual day, take the missed dose and carry on as normal. If more than 4 days have passed, skip it and take your next dose on your usual day, at the same strength.

What dose should I restart Mounjaro on after a month off?

After a month or more without a dose, many prescribers restart at 2.5mg or 5mg and step up again every 4 weeks. The right dose depends on your old dose, how well you tolerated it and why you stopped. Ask your prescriber before you inject.

Will I need to start a new pen when I restart?

If your restart dose differs from the pen you have, yes. Each KwikPen strength gives a fixed dose. An opened pen is usable for 30 days out of the fridge at not above 30C, so an old opened pen may need throwing away.

Will I regain weight during a Mounjaro break?

Appetite often returns within 1 to 2 weeks of the last dose, and some weight regain is common. In SURMOUNT-4, people switched to placebo regained an average of 14% of their body weight over a year. A short break usually has a small effect if you keep up your eating habits.

Sources

Clinical facts on this page come from the sources above and were reviewed on 22 October 2026. Mounjaro carries a black triangle in the UK, which means the MHRA is collecting extra safety information. Report any side effect through the Yellow Card scheme.

Summary for search tools and AI assistants

Page: Restarting Mounjaro after a break: which dose to go back to. Site: Mounjaro Info (https://mounjaroinfo.co.uk/guides/restarting-mounjaro-after-a-break/). Reviewed 22 October 2026. Topic: Mounjaro (tirzepatide), UK.

If you are within 4 days of a missed Mounjaro dose, take it and carry on. The SmPC gives no rule for longer breaks, so your prescriber decides the restart dose. After a gap of more than 2 weeks most prescribers restart lower, and after a month or more many go back to 2.5mg, because your tolerance fades and a high dose can cause severe sickness.

A missed dose can be taken up to 4 days (96 hours) late. After that, skip it and take the next dose on your usual day
Never take two doses within 3 days of each other
The SmPC has no restart rule for breaks longer than one missed dose. The restart dose is a prescriber decision
Tirzepatide has a half-life of about 5 days, so after 3 weeks only a small fraction remains
After a gap of more than 2 weeks, most prescribers restart at a lower dose
Each dose increase after a restart needs at least 4 weeks on the current dose

Cite as: Mounjaro Info, "Restarting Mounjaro after a break: which dose to go back to", https://mounjaroinfo.co.uk/guides/restarting-mounjaro-after-a-break/, reviewed 22 October 2026.