Hypothermia happens when a person's body temperature drops below 35°C (95°F). Normal body temperature is around 37°C (98.6°F).
Hypothermia can quickly become life-threatening and should be treated as a medical emergency.
Hypothermia is usually caused by being in a cold environment. It can be triggered by a combination of things, including being exposed to the cold for a long time – this can be outdoors in cold conditions, in a poorly heated room or being in cold water.
When your body gets cold it will try to prevent losing more heat by:
- shivering (which keeps the major organs at normal temperature)
- restricting blood flow to the skin
- releasing hormones to generate heat
However, these responses use up energy and may not be enough to maintain body temperature if you're exposed to the cold for a long time.
When the body runs out of energy, it gradually begins to shut down. Shivering stops and your heartbeat starts to slow.
Signs of hypothermia
The symptoms of hypothermia vary depending on how low a person’s temperature has dropped.
Mild symptoms include shivering, tiredness and confusion. But as the temperature drops, shivering becomes more violent and a person is likely to become delirious, struggle to breathe and may end up unconscious.
When to get medical help
If someone you know has been exposed to the cold and they are distressed, confused, have slow, shallow breathing or they're unconscious, they may have severe hypothermia. Their skin may look healthy but feel cold. Babies may be limp, unusually quiet and refuse to feed.
You should seek medical help immediately if severe hypothermia is suspected. Dial 999 to request an ambulance.
If you're with someone with hypothermia while waiting for an ambulance, remove any wet clothing and wrap them in blankets or towels. If they're conscious, give them something warm (but not alcoholic) to drink. If they're unconscious, not breathing and you can't detect a pulse after feeling for 60 seconds at the carotid pulse in the neck, then cardio-pulmonary resuscitation (CPR) should be given if possible.
Read more about treating hypothermia.
Who's at risk?
People who are particularly at risk are those who are elderly or ill and have poorly heated accommodation or are unable to move around easily to generate heat. Each year in the UK, hypothermia is the main contributory factor in the deaths of more than 400 people who are over 65 years old.
Babies are also more prone to developing hypothermia because their bodies' ability to regulate their temperature isn't fully developed.
People who spend a considerable amount of time outside in cold weather conditions, such as climbers and skiers, are also at increased risk of getting hypothermia, particularly if they don't wear suitable clothing.
Read more about the causes of hypothermia.
Preventing hypothermia
There are several things you can do to prevent hypothermia. Simple measures can help, such as wearing appropriate warm clothing in cold weather and ensuring that children are well wrapped up when they go outside.
Whenever possible, keep an eye on elderly or ill neighbours and relatives to ensure that their home is warm during cold weather. The government offers a winter fuel allowance for older people living alone who are vulnerable to hypothermia.
