BHF updates hot weather and heart guidance

The British Heart Foundation (BHF) updated its guidance page "Hot weather and your heart" on 6 July 2026, with the next review due 6 July 2029¹. The page sets out how heat affects the body and which groups the charity says are most at risk during hot weather and heatwaves¹.

The BHF says hot weather means the body has to work harder to keep its core temperature at a normal level, which can put extra strain on the heart, lungs and kidneys¹. It says the body widens blood vessels and the heart beats quicker to pump blood around, which "can cause your heart rate to increase and your blood pressure to drop", and that some people may feel dizzy or lightheaded¹. On who is most at risk, the charity lists older people over 75 and very young children, people with long-term conditions including heart or circulatory conditions, lung conditions, kidney problems, diabetes and Parkinson's disease, and people who find it harder to avoid the heat or adapt their behaviour, such as people who are bedbound, have a disability, dementia, or work outdoors¹. It adds that older people can be at higher risk because they are more likely to live on their own and have less social contact¹.

The guidance covers medicines and specific heart conditions. It says most medicines need to be stored at temperatures under 25C, that medicines which warm up too much "may not work as well as they're supposed to", and that they should be kept in a cool, dark place such as a cupboard, away from windows and radiators, and not left in a car¹. It says people who use a GTN spray for angina should take extra care in hot weather because the spray can dilate blood vessels quickly, causing blood pressure to drop suddenly with possible dizziness and faintness¹. For heart failure, it says anyone told to restrict their fluid intake should speak to their GP about other ways to keep cool, and that people taking water tablets (diuretics) who feel dizzy or lightheaded should let their doctor know¹.

On staying cool, the BHF advises keeping windows shut when the outside temperature is hotter than inside the home and closing curtains or blinds to keep out the sun, opening windows in the evening when it cools down, and turning off unneeded lights and electrical equipment¹. It advises staying out of the sun during the hottest part of the day, between 11am and 3pm, going out with sunscreen, a hat and water, and limiting tea and coffee to no more than 3 to 5 cups a day or switching to decaffeinated versions¹. It also advises avoiding some types of exercise, such as running and football, which it says can make people very hot and dehydrated and put extra pressure on the heart¹.

The charity lists symptoms of heat stroke as sweating, cold clammy skin, dizziness, fainting, muscle cramps, heat rash, swelling (oedema) in the ankles, shallow or fast breathing, and feeling sick or being sick¹. It says losing too much body fluid can raise internal body temperature, which could be life-threatening if left untreated¹. For someone feeling ill in the heat, it gives four steps: move to a cool place, lie down and raise the feet slightly, drink plenty of water, and cool the skin with a cold shower, a fan or ice packs; if they do not start to feel better, it says to contact NHS 111 or a doctor¹.

Why it matters for households

The guidance is aimed at people living with heart and circulatory conditions and those who care for them, and it applies through any spell of hot weather rather than from a fixed date. It sets out who the BHF considers more at risk, including people over 75, very young children and people with long-term conditions, and it advises checking on friends and family regularly in hot weather to make sure they are cool and comfortable¹. For households managing medicines, it gives storage temperatures and warns that heat can affect how well medicines work¹. It also flags specific points for people with angina or heart failure, including fluid restriction and diuretics¹. The charity's general position is that it is particularly important for people with a heart condition to stay cool and hydrated¹.

What happens next

The page carries a next review date of 6 July 2029¹. No further update or publication has been reported. The BHF's Heart Helpline, which it says can be reached by phone, callback, email or online chat, runs Monday to Friday, 9am to 5pm¹. General household preparation for hot weather is covered in the guide to heatwaves and drought.