​UK Heatwave 2026: What to know if you’re taking painkillers, insulin, or antidepressants, and safety tips from the MHRA​

Britain’s 2026 heatwave is no longer just about melting train platforms, sleepless nights, and desperate supermarket fan shortages. This sweltering heatwave, with temperatures crossing 35°C in several places, is turning out to be more than just a daily hassle with heat, humidity, and unusual discomfort. Temperatures across parts of England continue climbing above seasonal averages, leading to growing concern about dehydration, heat exhaustion, and medicine-related complications — especially among older adults and people with chronic health conditions. And this time, there’s a bigger health concern that’s flying under the radar: how all this heat messes with everyday medicines, and might catch people off guard.

The UK’s Medicines and Healthcare products Regulatory Agency (MHRA) is urging everyone to pay close attention to how they use and store their medications. When it’s this hot, common drugs can start behaving in ways people don’t expect. Heat messes with how some medicines work, how your body processes them, and whether they even stay safe or effective.

What’s really at stake here? Not just headaches and restless nights, but real risks like dehydration, heat exhaustion, and medicine-related complications, especially for older people and folks dealing with things like diabetes, heart problems, or mental health conditions. Medicines you use all the time — ibuprofen, diabetes pills or injections, blood pressure meds, antidepressants — can throw new problems into the mix during a heatwave. Heat can actually damage them if you don’t store them right, but sometimes the drugs themselves make you more likely to overheat, dry out, or get sunburned. The MHRA’s advice is pretty clear: double-check your medicine storage, don’t skimp on water, and don’t ignore weird new symptoms as the temperatures rise.

Why does this matter? Because heat changes how your body handles medication, and some medications don’t like heat much either.

People often don’t think about this. For most, taking medicine is just one of those boring routines. But medicines break down in the heat, or suddenly get stronger, or sometimes start causing trouble your body normally shrugs off.

The biggest issue the MHRA points to? Storing your medicines the wrong way. Most are only meant to stay below 25°C. But let’s face it, when it’s boiling outside, inside your flat, car, handbag, or just baking by a window, things heat up way past that, ruining everything from painkillers to insulin, hormone patches, even inhalers and emergency allergy injectors. Anything that’s supposed to be kept cold is in particular danger.

So, make sure to watch for obvious signs: if pills look weird, liquids separate or smell off, or your inhaler just stops working, talk to your pharmacist right away.

If you have diabetes, heart disease, or mental health conditions, these risks double up: dehydration (thanks to both the heat and some meds), overheating, and taking pills that could already be less effective.

Here’s where you need to be extra careful:

First comes painkillers, like ibuprofen and naproxen, which are popular but can make you burn faster in the sun, and sometimes without you realizing it. If you’re outside a lot, pair these with sunscreen and hats. Also, taking NSAIDs while dehydrated puts extra strain on your kidneys. So don’t forget the water bottle.

Then, there are Prescription meds that cause other headaches. Diuretics ("water tablets") like furosemide ramp up how much you pee. Pair that with heat, and you’ll dry out fast. Blood pressure meds (ACE inhibitors, beta-blockers, calcium channel blockers) can mess with your body’s ability to stay cool or recognize thirst. That’s a straight shot to dizziness, fainting, or heat exhaustion.

What about diabetes meds? Of course, they’re a big concern. Insulin is really sensitive to high temperatures. Leave it somewhere hot, and it can stop working, sending your blood sugar on a rollercoaster. Heat can also mess up your blood glucose meter’s readings or ruin test strips. The MHRA says: keep insulin refrigerated, use cool bags while out, and check for any signs it’s off before using it.

Then there’s Metformin, which isn’t as touchy about heat, but it can leave you dehydrated. And being dehydrated while on metformin bumps up your risk of lactic acidosis, which is rare but dangerous. The problem is, dehydration often sneaks up on people in hot weather since it looks a lot like basic heat exhaustion — think fatigue, headaches, and even dizziness.

Then comes one of the most sensitive lots: antidepressants. Some (SSRIs like sertraline or fluoxetine) can mess with your ability to sweat or keep your core temp steady. Tricyclics like amitriptyline can drag you into dehydration or make overheating worse. All this, in a country where few homes have real air conditioning.

Now, let’s be honest — British housing doesn’t help much in the heatwave. That’s largely because most places are built to hold in heat, not let it out. If you live alone, are older, or already have health problems, you’ll probably feel the strain even more. The MHRA’s top line is: don’t just stop your meds because it’s hot; talk to your doctor first. But do pay attention to how you store them and how you feel when you take them.

As for their key advice, here they are.

Always keep meds in a cool place, out of sunlight, and away from steamy bathrooms. Most medications are meant to be kept below 25°C, yet cars, buses, bedrooms, and handbags can quickly exceed that temperature during hot weather. Even leaving medicines near sunny windows can damage active ingredients. Living rooms or cupboards away from windows are usually safest — away from direct sunlight and humidity. Bathrooms, ironically, are often poor storage locations because steam and heat fluctuations can affect medications over time.

Hydration is huge, and MHRA agrees too — especially if you’re on diabetes meds, antidepressants, diuretics, or blood pressure tablets, drink regularly, even before you feel thirsty. Dehydration symptoms can include dark urine, confusion, headaches, dizziness, dry mouth, and unusual fatigue. The danger becomes especially serious for elderly people, children, and those living alone.

Another common mistake during heatwaves is assuming indoor spaces are automatically safe. In reality, indoor overheating has become one of Britain’s fastest-growing summer health risks. During previous major UK heatwaves, thousands of excess deaths were linked to prolonged exposure to high temperatures. Don’t assume you’re safe just because you’re not outside.

Sun protection is another big one. A lot of meds can make your skin more sun-sensitive (not just antibiotics, but painkillers, acne meds, methotrexate, and antidepressants). Read the leaflets, use sunscreen, hats, and cover up if you’re outside for a while. Also, it’s advisable to avoid excessive alcohol, limit direct afternoon sun exposure, and wear lightweight clothing during the hottest hours of the day.

This one’s very important to remember: don't sit on odd symptoms. If you, or a friend, start dealing with confusion, fainting, chest pain, trouble breathing, or major dehydration, get help now. Especially for those on antidepressants, signs like overheating, excessive sweating, confusion, dizziness, or just feeling extremely wiped out are red flags.