People taking common medications, including for blood pressure, asthma and diabetes, have been warned to ensure they are stored in appropriate conditions as the UK heatwave continues this weekend. The Medicines and Healthcare products Regulatory Agency (MHRA) said high temperatures can affect medicines and how well they work, and hot weather can also change how your body responds to drugs.
Dr Alison Cave, chief safety officer at the MHRA, said: “Let’s face it — when there’s a heatwave, most of us are focused on getting outside and enjoying it while it lasts. But it’s easy to forget that medicines left in the heat – in cars, bags, or on sunny windowsills — might not work properly when you need them. Some medicines can also make you more likely to burn in the sun, feel dizzy, or get dehydrated, especially if you’re taking diuretics or have a condition like asthma, heart disease, or diabetes.”
Dr Cave shared three clear tips for staying safe in the heat. First, medicines should be stored in cool, dry places out of direct sunlight.
Most medicines need to be kept below 25°C. Others need to be kept in the fridge so it is important to check labels and packaging for storage instructions.
Heat can breakdown the active ingredients in medicines such as tablets, inhalers, hormone patches, insulin and EpiPens.
If medcieijs change colour, develop an unusual smell, change texture or look different to normal, these could be signs of heat damage and you should seek advice from a pharmacist.
The second tip is to know the signs of heat-related illness, stay hydrated and listen to your body.
Your body loses more water through sweating during hot weather, and some medicines can make this worse or make it harder for your body to cope with heat.
People taking diuretics, or “water tablets”, such as furosemide, are already losing more fluid through urination, which can lead to dehydration or mineral imbalances.
Blood pressure medicines such as ACE inhibitors, beta-blockers, or calcium channel blockers can also make it harder for your body to regulate temperature, especially during sudden hot spells.
And some diabetes medicines, including insulin and metformin, also increase the risk of dehydration or make early symptoms harder to spot.
If you start to feel unwell in the heat, Dr Cave advised you should move somewhere cooler, sip water slowly, and seek medical advice if you do not feel better quickly.
Finally, Dr Cave advised people to check whether their medication can make their skin more likely to burn, even in mild sunshine.
This includes some antibiotics, diuretics, antidepressants, or skin treatments for acne or eczema. Painkillers such as ibuprofen or naproxen are also known to sometimes cause mild sun sensitivity, but this is less common and usually only a concern with frequent or long-term use.
Methotrexate, used to treat conditions like rheumatoid arthritis, psoriasis, Crohn’s disease and cancer, can particularly cause extreme skin sensitivity to the sun even at low doses.
Consequences can include painful rashes, blistering or swelling and, in rare cases, serious infections. Dr Cave added: “Remember, for all medicines it’s important to read the leaflet and speak to a healthcare professional if you have any questions.”
