Heat cramps: muscle cramps in hot weather and when they signal heat exhaustion

A cramp is a sudden, painful tightening of a muscle. The NHS describes leg cramps as a muscle in the leg tightening and causing a sudden pain that can make it hard to move, lasting from a few seconds to 10 minutes, with the muscle sometimes sore for up to 24 hours afterwards. Heat cramps are cramps that occur in hot weather or during hot, strenuous activity.

The NHS does not use heat cramps as a separate heading. It treats cramps as one of the symptoms of heat exhaustion, and as a possible effect of strain on muscles that is worse in hot or humid weather, together with dehydration. That is why this page draws on its heat exhaustion, heatwave and leg cramp pages.

In hot weather the body loses water and salt through sweat. The NHS says a heatwave can cause dehydration and overheating, and recommends an isotonic sports drink or oral rehydration powder to help replace the salt lost. For leg cramps in general the NHS lists strain on muscles during exercise, which can be worse in hot or humid weather, dehydration, certain medicines such as statins and diuretics, pregnancy, ageing and alcohol-related liver disease.

Because several of those causes can overlap, a person who cramps in the heat may be dehydrated, may be taking a medicine that contributes, or may be developing heat exhaustion. The NHS also notes that the reason for some cramps is unknown.

The cramp itself is usually obvious, but the surrounding picture tells you whether it is part of heat exhaustion. The NHS lists these symptoms of heat exhaustion, which are often the same in adults and children.

• Tiredness, dizziness and headache.

• Feeling or being sick.

• Excessive sweating and skin becoming pale and clammy.

• Cramps in the arms, legs and stomach.

• A high temperature, being very thirsty and feeling irritable.

For heat exhaustion, the NHS gives four steps: move the person to a cool place; remove unnecessary clothing such as a jacket or socks; give plenty of water to drink, with an isotonic sports drink or oral rehydration powder helping to replace salt; and cool the skin by spraying or sponging with cool water and fanning, with cold packs wrapped in cloth under the armpits or on the neck. Stay with them until they are better. They should start to cool down and feel better within 30 minutes.

For the cramp itself the NHS says stretching and massaging the muscle may ease the pain, though most cramps go away without doing anything, and standing and putting weight on the leg with the cramp may help. Paracetamol or ibuprofen can help with soreness afterwards but will not help while the cramp is happening because they take too long to work.

The NHS says heat exhaustion does not usually need emergency medical help if you can cool down within 30 minutes. It advises getting help from NHS 111 if you or someone else has symptoms of heat exhaustion that you are struggling to treat.

It says to call 999 for signs of heatstroke: still being unwell after 30 minutes of resting in a cool place, being cooled and drinking fluids; a very high temperature; hot skin that is not sweating and might look red; a fast heartbeat; fast breathing or shortness of breath; confusion and lack of coordination; a seizure; or loss of consciousness. While waiting, wrap the person in a cool, wet sheet or fan and sponge them with cold water, and if they lose consciousness put them in the recovery position. Do not drive yourself to A&E.

For leg cramps in general, the NHS advises seeing a GP if cramps disturb your sleep, if you also have numbness or swelling in your legs, or if cramps last longer than 10 minutes.

The NHS suggests drinking more cold drinks, especially if active or exercising, wearing light-coloured loose clothing, avoiding the sun between 11am and 3pm, avoiding drinking too much alcohol, avoiding extreme exercise, and keeping the home cool by closing curtains and windows if it is hotter outside than in. Its heatwave advice adds having cold food and regular cold drinks, avoiding caffeine and hot drinks, and taking a cool shower or putting cool water on your skin or clothes.

For recurring night-time cramps, the NHS says regular calf-stretching exercises may help reduce them, by standing facing a wall and leaning forward until the calf muscles stretch, but may not stop them completely.

The NHS lists those more vulnerable in a heatwave: older people, especially those aged 65 and over; babies and young children aged 5 and under; people who are pregnant or have serious long-term conditions such as heart or breathing problems, dementia, diabetes, kidney disease, Parkinson's disease, mobility or mental health problems; people who live alone; people on multiple medicines; people who are already ill and dehydrated; and people who work or spend a lot of time outside or whose jobs involve manual labour. It says to check on anyone at higher risk.

Most heat cramps are managed at home with cooling and fluids, and NHS 111 or a GP can advise if symptoms persist or recur. The NHS says a GP will examine you to try to find the reason for leg cramps and suggest treatment depending on the cause, and private GP services can offer a similar assessment. The point is not to rely on cramps settling by themselves if they are accompanied by confusion, a high temperature or hot dry skin, which need emergency care.