How long can Mounjaro stay out of the fridge?
Once you've started a Mounjaro (tirzepatide) KwikPen, the UK leaflet allows up to 30 days out of the fridge at no more than 30 °C, then the pen must be thrown away. Before first use, keep it in the fridge at 2–8 °C. Never use a pen that has been frozen.
- GLP‑1 medicines are prescription-only in the UK, not sold over the counter.8
- Every figure below comes from the UK product information for each pen, named each time.
- Ask a pharmacist about a pen that has been too warm or frozen.
How long can an opened Mounjaro KwikPen stay out of the fridge?
The UK leaflet says an opened Mounjaro KwikPen can be kept unrefrigerated, up to 30 °C, for 30 days, then thrown away.2
The UK SmPC uses the same words: "for up to 30 days at a temperature not above 30 °C and then the pre-filled KwikPen must be discarded".1 Each KwikPen holds 4 weekly doses, so a pen normally lasts 4 weeks.1
Lilly's UK medical information says moving an opened pen in and out of the fridge within the 30 days "does not impact product quality".3 It adds that you should never store the pen with the needle attached.3
Can an unopened Mounjaro pen be left out?
The UK product information gives no time out of the fridge for a pen you haven't started, and says to keep it at 2–8 °C.1,2
The US label is looser. It allows an unopened KwikPen up to 30 days at room temperature, up to 30 °C.4 That is why some advice online differs from the UK leaflet. Lilly's UK page gives the same fridge rule for unopened pens.3
What about frozen pens and hot places?
Every UK Mounjaro document we read sets 30 °C as the limit, and the leaflet says never to use a pen that has been frozen.1,2,3
The leaflet's words are "If the pen has been frozen, DO NOT USE."2 It also says not to use a pen that is damaged, or where the medicine is cloudy, discoloured or has particles in it.2 Lilly says to make sure an in-use pen "is not exposed to temperatures above 30 °C".3 Flights and hot holidays are covered in Travelling abroad with weight-loss pens.
How does that compare with Wegovy and Ozempic?
Opened Wegovy FlexTouch and 4-dose Ozempic pens last longer, 6 weeks below 30 °C or in the fridge, under their UK SmPCs.5,7
| Pen | Out of the fridge (UK SmPC) |
|---|---|
| Mounjaro KwikPen, opened | Up to 30 days, not above 30 °C1 |
| Wegovy FlexTouch, opened | 6 weeks, below 30 °C or in the fridge5 |
| Wegovy 7.2 mg single-dose pen | Up to 28 days, not above 30 °C, then throw away6 |
| Ozempic, opened | 6 weeks (4-dose pens); 8 weeks (1 mg 8-dose pen); below 30 °C or in the fridge7 |
Wegovy and Ozempic pens should keep their cap on to protect them from light.5,7 Used pens and needles are covered in How do I dispose of used pens and needles in the UK?
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Related questions
Sources
- Eli Lilly. Mounjaro KwikPen (tirzepatide) UK summary of product characteristics (SmPC), date of revision 29 Aug 2026, sections 4.4, 4.5, 4.6, 6.3, 6.4 and 6.6. UK label. medicines.org.uk (emc)
- Eli Lilly. Mounjaro KwikPen (tirzepatide) UK patient information leaflet, last revised Aug 2026, sections 2, 3, 4 and 5. UK label. medicines.org.uk (emc)
- Lilly Medical (UK). How should the Mounjaro (tirzepatide) KwikPen be stored? Last reviewed 27 May 2026. Maker's medical information for UK healthcare professionals; not a label. medical.lilly.com
- Eli Lilly. Mounjaro (tirzepatide) US prescribing information, revised 08/2026, section 16.2. US label, not the UK one. pi.lilly.com
- Novo Nordisk. Wegovy 2.4 mg FlexTouch (semaglutide) UK SmPC, date of revision 09/2026, sections 4.1 and 6.3. UK label. medicines.org.uk (emc)
- Novo Nordisk. Wegovy 7.2 mg single-dose pen (semaglutide) UK SmPC, date of revision 09/2026, sections 6.3 and 6.4. UK label. medicines.org.uk (emc)
- Novo Nordisk. Ozempic (semaglutide) UK SmPC, date of revision 07/2026, sections 4.1 and 6.3. UK label. medicines.org.uk (emc)
- MHRA. First GLP-1 tablet for weight loss approved in the UK. Press release, 11 Jun 2026 ("As with all GLP-1 receptor agonists, this is a prescription-only medication"). gov.uk
Last checked 12 Oct 2026 · Next review due 12 Oct 2027 · Report an error
How this answer was made. Written by the GLP Guidebook team from the sources above. It's general information, not medical advice. Talk to a pharmacist about a pen that has been too warm or frozen, and to a qualified doctor before starting, stopping or changing any medicine. How we write