Wegovy and Mounjaro in a heatwave: what to do
Anna-Louise Dearden | Last update: 27th June 2025
Depending on who you believe over a million of us are on weight loss drug jabs– but when temps hit the 30s, like the last few weeks, things can get more than a little…sweaty. If you’re on Wegovy and Mounjaro in a heatwave this summer, here’s what you need to know to keep your pens (and your body) working during a heatwave. Injecting a jab that’s been rolling around a baking-hot glovebox for three days is not a good idea.
TL;DR: Jab-Safe in the Sun
Wegovy and Mounjaro in a heatwave – the pens don’t like it hot – keep them under 30°C, or ideally in the fridge
Flying? Pens go in your carry-on, never the hold
Hydration is non-negotiable. Nausea + heat = dehydration risk
Check before you inject – cloudy or clumpy? Bin it
Heat & meds = sunscreen central – GLP-1s may increase sun sensitivity
Your weight loss pen has a meltdown limit
Wegovy and Mounjaro are temperature-sensitive little divas. Anything over 30°C and you risk ruining the medicine. Most pens are OK out of the fridge for around 30 days (some 42 – check your leaflet), but only if it stays under 30°C. And guess what? A hot UK kitchen windowsill definitely isn’t under 30°C.
James O’Loan, obesity specialist and weight loss injection expert at Chemist4U, says: “Weight loss injections can be adversely affected by hot weather, particularly regarding storage and stability. Understanding the storage instructions when using any prescribed medication is vital to keep it in optimal condition.
“To be safe in a heatwave, store your pen in the fridge whenever possible – between 2–8°C. If you’re not sure it’s safe to use, don’t inject. Check for cloudiness or floating particles.”
Off on hols? Don’t pack your jab in the hold!
If you’re jetting off soon, did you know your injection must travel in your hand luggage? Luggage holds can drop to sub-zero temps mid-flight. And frozen pens means dead pens.
Lee Frost, a practitioner in Northamptonshire often consults with clients travelling. “Stick your injection in a mini cool bag and keep it close. It’s also a good idea to check if your hotel room has a fridge that you can use. You should also take a small sharps bin to dispose of any needles or ask the hotel or a local pharmacy for assistance in disposing of them.”
Understanding the care and attention that may need to go into travel with the treatments, do people really need to take them on their travels?
“I am being asked this all of the time now summer is here,” says Frost. “I would say 80% of my patients decide not to take it away with them and inject the day before and the day of their return.”
If you do decide to take them, Lee says there are a lot of countries that freely allow prescription only medications including Mounjaro, Ozempic and Wegovy. But bring a copy of your prescription, in case airport security gets curious.
“Documents such as a doctor’s note or a prescription can sometimes be required, so better safe than sorry, and make sure you have these documents to hand when traveling with your medication. You can check the rules of the country you are going to on the Government website.”
Heat + nausea = dehydration central
You know that mild nausea you sometimes get post-jab? Crank that up with heatstroke and you’re headed for a dizzying few hours. Throw in a bit of holiday diarrhoea or dodgy BBQ, and you could end up seriously dehydrated.
James’ advice: “Drink little and often – don’t wait to feel thirsty. If you’re sick or have diarrhoea, use an electrolyte drink to rehydrate quickly. And don’t forget the sunscreen – some users report increased UV sensitivity.”
Is it the heat… or the jab?
Extreme heat can amplify side effects – fatigue, dizziness, tummy troubles – which already come with the territory on GLP-1s. Listen to your body. Sit down. Shade up. Cancel plans. Whatever you need to do.
Your SlimrChat ‘Summer jab-safe’ takeaway:
- Keep it cool: Store pens at 2–8°C when you can, and never above 30°C.
- Plan ahead for travel: Take pens in your carry-on, use a cool pouch, and bring your prescription.
- Hydrate like a boss: Drink water regularly, especially if feeling dizzy or sick.
- Check the pen: No weird floaters or cloudiness. If in doubt? Chuck it out.
Hot girl summer, yes. Hot jab summer? Nope. Stay cool, stay safe – and if your meds are cooking in your bag, they’re probably not working anymore.
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