Storing weight loss pens comes down to three rules: keep unused Mounjaro and Wegovy pens in the fridge at 2°C to 8°C, never let them freeze, and respect the time limit once a pen is in use. As of September 2026, the UK leaflets allow a Mounjaro KwikPen up to 30 days at no more than 30°C after first use, and a Wegovy FlexTouch pen 6 weeks below 30°C or in the fridge. When that window closes, the pen is finished, even if there's medicine left inside.
This article is information only, not medical advice. Mounjaro and Wegovy are prescription-only medicines, and a qualified prescriber decides whether they're suitable for you. Storage instructions can differ between brands and types of pen (NHS), so the leaflet in your box is the final word.
What are the rules for storing weight loss pens?
Every pen starts in the fridge at 2°C to 8°C, and none may be frozen (Mounjaro KwikPen SmPC; Wegovy SmPC).
Mounjaro KwikPen
- Before first use: fridge, 2°C to 8°C. If the pen has been frozen, do not use it.
- After first use: it can be kept unrefrigerated at not above 30°C for up to 30 days, then the pen must be discarded (Mounjaro leaflet). The UK wording doesn't say whether refrigeration changes that, but the EU product information for the same pen says to discard it 30 days after first use (EMA), so count from your first injection.
Wegovy FlexTouch pen
- Before first use: fridge, 2°C to 8°C, away from the cooling element.
- During use: 6 weeks, below 30°C or in the fridge; the SmPC says the fridge is preferable.
- Light: keep the pen cap on, and don't inject Wegovy that has been exposed to direct sunlight (Wegovy leaflet).
- 7.2 mg taken as three 2.4 mg injections: the leaflet says partially used pens must go back in the fridge with the needle removed.
Wegovy 7.2 mg single-dose pen
The MHRA approved this one-injection pen on 14 April 2026 (MHRA). Keep it in its original carton to protect it from light; it can be kept unrefrigerated for up to 28 days at not above 30°C. Discard it if it has been exposed to light or temperatures above 30°C, out of the fridge for more than 28 days, or frozen (Wegovy 7.2 mg leaflet). More on each device: our Mounjaro pen page and Wegovy pen page.
How long can a weight-loss pen stay out of the fridge?
For a multi-dose pen, the clock starts with your first injection: up to 30 days for a KwikPen, 6 weeks for a FlexTouch pen. Four weekly doses take three weeks from first injection to last, leaving room for a delayed dose but not a long break. Write the start date on the carton.
Before first use, KwikPen and FlexTouch pens belong in the fridge; only the single-dose 7.2 mg pen has a 28-day allowance before its one injection. If an unused pen was left out, ask the dispensing pharmacy before using it.
What happens if my pen freezes or gets too hot?
Freezing is the one mistake you can't undo: all three UK leaflets say not to use a pen that has been frozen. Both Wegovy leaflets say to keep pens away from the fridge's cooling element, and for the same reason never pack a pen straight against an ice pack.
Heat is the other risk. All three leaflets set 30°C as the ceiling for unrefrigerated storage, and the 7.2 mg leaflet says to discard a pen exposed to anything hotter. Think hot cars, sunny windowsills and radiators. If a pen may have got hotter than 30°C, speak to a pharmacist before injecting.
Check before every injection. Mounjaro should be clear and colourless to slightly yellow, Wegovy clear and colourless. Don't use a damaged pen or medicine that is cloudy, discoloured or has particles.
Where is the best place to keep a pen in the fridge?
- In its carton, on a main shelf, away from the cooling element and any freezer compartment. The expiry date after "EXP" means the last day of that month.
- Cap on, needle off. The Wegovy leaflet says never to store your pen with the needle attached, to prevent blocked needles, contamination, infection and inaccurate dosing. Our guide to needle size, single use and disposal explains more.
- Out of sight and reach of children, as every leaflet says.
Does a pen need to arrive cold?
Put a delivered pen in the fridge as soon as it arrives. Wegovy's product information says its data support controlled shipment to the patient below 30°C for up to 48 hours (Wegovy 7.2 mg SmPC); that covers controlled delivery, not leaving pens out, and the UK Mounjaro product information has no such statement. If a parcel was badly delayed, damaged or warm, ask the dispensing pharmacy before use.
The MHRA says only a legitimate pharmacy, including online ones, with a prescription can guarantee a genuine GLP-1 medicine. It warns against unregulated sellers such as beauty salons and social media, and against counterfeit pens that closely mimic the real thing (MHRA).
How do I store my pen when travelling?
Keep your pen in your hand luggage, not checked baggage or a parked car. The UK's National Travel Health Network and Centre (NaTHNaC) advises carrying medicines in their original labelled pharmacy packaging with a copy of your prescription and a prescriber's letter, telling your airline in advance about injectable medicines, and checking they're permitted where you're going.
At UK airports, GOV.UK lists essential liquid medicines, hypodermic syringes and cooling gel packs as allowed in hand luggage; for ice packs, contact the airport (GOV.UK). Frozen items usually can't go in hand luggage, and liquid rules have changed at some UK airports, so check with yours before you travel (GOV.UK). Proof of prescription is only required for liquid medicine in containers over 100ml (a KwikPen holds 2.4ml), but carry it anyway. In a cool bag, wrap the pen so it never touches the cold pack. Our guide to using your pen covers the travel routine.
How do I throw away old, expired or frozen pens?
Not down the sink or in household rubbish: every leaflet says to ask your pharmacist how to throw away medicines you no longer use. The Wegovy FlexTouch leaflet says to dispose of needles and empty pens as your doctor, nurse, pharmacist or local authority instructs; the cap and empty carton can go in household waste. A little medicine left after the last dose is normal, so don't try to use it.
If you think a pen was faulty or not genuine, or you have a side effect you're worried about, speak to your pharmacist or doctor and report it through the MHRA Yellow Card scheme. See our side effects page and FAQ.
Frequently asked questions
Do weight loss pens need to be kept in the fridge?
Yes, as a rule: unused Mounjaro and Wegovy pens belong at 2°C to 8°C, never frozen. Limited time out is then allowed: 30 days for a started KwikPen, 6 weeks for a started FlexTouch pen and 28 days for the single-dose Wegovy 7.2 mg pen.
How long can Mounjaro stay out of the fridge?
As of September 2026, the UK leaflet allows a started KwikPen up to 30 days unrefrigerated at not above 30°C, then it must be discarded. The EU product information says to discard it 30 days after first use, so count from your first injection.
How long can a Wegovy pen stay out of the fridge?
A started Wegovy FlexTouch pen can be kept for 6 weeks below 30°C or in the fridge. The single-dose Wegovy 7.2 mg pen allows up to 28 days unrefrigerated at not above 30°C, in its carton.
Can I use a pen that has been frozen?
No. The UK leaflets say not to use Mounjaro or Wegovy that has been frozen, even if it has since thawed. Ask your pharmacist what to do next.
Can I take my weight loss pen on a plane?
Generally, yes. At UK airports, GOV.UK lists essential liquid medicines, hypodermic syringes and cooling gel packs as allowed in hand luggage. Carry the pen in its labelled pharmacy packaging with a copy of your prescription, and check airline and destination rules.