Heat exhaustion and heatstroke are two potentially serious conditions that can occur if you get too hot.
They usually happen during a heatwave or in a hot climate, but can also occur when you're doing very strenuous physical exercise.
Heatstroke is less common, but more serious. It can put a strain on the brain, heart, lungs, liver and kidneys, and can be life-threatening.
If heat exhaustion isn't spotted and treated early on, there's a risk it could lead to heatstroke.
Heat exhaustion or heatstroke can develop quickly over a few minutes, or gradually over several hours or days.
Signs of heat exhaustion can include:
If left untreated, more severe symptoms of heatstroke can develop, including confusion, disorientation, seizures (fits) and a loss of consciousness.
If you notice that someone has signs of heat exhaustion, you should:
Stay with the person until they're feeling better. Most people should start to recover within 30 minutes.
If the person is unconscious, you should follow the steps above and place the person in the recovery position until help arrives (see below). If they have a seizure, move nearby objects out of the way to prevent injury.
Severe heat exhaustion or heatstroke requires hospital treatment.
You should for an ambulance if:
Continue with the treatment outlined above until the ambulance arrives.
If the person is feeling better after using the above measures, but you have any concerns about them, contact your doctor for advice.
Anyone can develop heat exhaustion or heatstroke during a heatwave or while doing heavy exercise in hot weather. However, some people are at a higher risk.
You're more likely to experience problems if you're dehydrated, there's little breeze or ventilation, or you're wearing tight, restrictive clothing.
Certain medications can also increase your risk of developing heat exhaustion or heatstroke, including diuretics, antihistamines , beta-blockers , antipsychotics and recreational drugs, such as amphetamines and ecstasy.
Heat exhaustion and heatstroke can often be prevented by taking sensible precautions when it's very hot.
During the summer, check for heatwave warnings, so you're aware when there's a potential danger. The government uses a system called Heat-Health Watch to warn people about the chances of a heatwave. This is a system of four different warning levels based on the expected temperature.
If you're new to a hot country, be particularly careful for at least the first few days, until you get used to the temperature.
If you’re not urinating frequently or your urine is dark, it's a sign that you're becoming dehydrated and need to drink more.
In the longer term, it can help to have your loft and cavity walls insulated, as this will keep the heat in when it's cold and keep it out when it's hot. Using light-coloured, reflective external paint on your house may also be useful.
Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.