MHRA heat warning: essential medicine storage advice for UK patients
MHRA heat guidance: protect your medicines this week
The Medicines and Healthcare products Regulatory Agency (MHRA) has re-issued its guidance on protecting medicines during extreme heat, with temperatures in parts of the UK expected to surpass 30C on Monday and remain in the mid-to-high 20Cs for the rest of the week. The advice is particularly relevant to the millions of people taking commonly prescribed medicines.Among the medicines highlighted are ACE inhibitors such as ramipril, used to treat high blood pressure and heart failure, and beta-blockers like bisoprolol, prescribed for angina, high blood pressure and heart failure. The guidance also covers diabetes medicines, antipsychotics, stimulants and diuretics.Alison Cave, chief safety officer at the MHRA, said: "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."

Why heat affects medication

The MHRA states that most medicines require storage at temperatures below 25C, a threshold that homes, workplaces, vehicles and schools have regularly exceeded this summer and may do so again in the coming days. Heat breaks down the active ingredients in medicines, and medications requiring refrigeration are especially vulnerable. If medicine is compromised by heat, it may cease to work effectively.

How medicines can change your body's response to heat

While it is well known that the body loses more water through sweating in warm weather, the MHRA notes that some medicines can make this worse or make it harder for the body to cope with heat. Blood pressure medicines such as ACE inhibitors, beta-blockers, or calcium channel blockers can make it harder for the body to regulate temperature, especially during sudden hot spells. ACE inhibitors can even suppress the natural thirst response.The agency also highlights other medicines that can increase risk during warm weather:
  • Diabetes medicines, including insulin and metformin, can increase the risk of dehydration or make early symptoms harder to spot.
  • Antipsychotic medications, such as olanzapine or quetiapine, or stimulant medications for attention disorders, can increase body temperature and make overheating more likely.
  • Diuretics, or water tablets, such as furosemide, cause additional fluid loss through urination.
Certain common medicines can also heighten vulnerability to sunburn, including some antibiotics, diuretics, antidepressants, and skin treatments for acne or eczema.

Signs of dehydration

Dehydration can cause dizziness, headaches, tiredness, confusion, and darker urine. This is particularly dangerous for older people, young children, and those with heart or kidney conditions. If you start feeling unwell in the heat, move to a cooler place, drink water slowly, and seek medical help if your condition does not improve quickly.

Keeping medicines safe in hot weather

The MHRA advises:
  • Store medicines somewhere cool, dry and out of direct sunlight.
  • Avoid leaving them in cars or in bags left in sunlight.
  • Know the signs of heat-related illness.
  • Stay hydrated and listen to your body.
  • Take extra care in the sun if your medicine makes your skin more likely to burn.
  • Read the leaflet and speak to a healthcare professional if you have any questions.