Hypothermia occurs when a person's body temperature drops below 35C (95F). Normal body temperature is around 37C (98.6F).

Hypothermia can quickly become life threatening and should be treated as a medical emergency.

It's usually caused by being in a cold environment and can be triggered by a combination of factors, such as being outdoors in cold conditions for a long time, living in a poorly heated house or falling into cold water.

Who's at risk?

People who are unable to move around to generate heat, such as the elderly or those who are ill, are at particular risk of developing hypothermia.

During 2013-14, more than 1,600 people seen in hospital were diagnosed with hypothermia. Just over 70% of these cases were people over 60 years of age.

Babies are also more prone to developing hypothermia because their bodies' ability to regulate temperature isn't fully developed.

But it's not just babies and elderly or ill people who develop hypothermia. Anyone who spends long periods outside during the winter without wearing appropriate warm clothing can also be at risk, particularly after drinking large amounts of alcohol.

For example, in recent years there have been several cases of young people developing hypothermia after getting drunk on a night out and failing to find their way home, wearing only light clothes.

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.

Signs of hypothermia

The signs of hypothermia vary depending on how low a person's temperature has dropped. Initial symptoms include shivering, tiredness, fast breathing and cold or pale skin.

As the temperature drops, shivering becomes more violent, although it will stop completely if the hypothermia gets worse. The person is likely to become delirious and struggle to breathe or move. They may lose consciousness.

Babies with hypothermia may look healthy, but their skin will feel cold. They may also be limp, unusually quiet and refuse to feed.

Read more about the symptoms of hypothermia.

When to get medical help

You should seek immediate medical help if you suspect someone has hypothermia.

If someone you know has been exposed to the cold and they're distressed, confused, have slow, shallow breathing or they're unconscious, they may have severe hypothermia. In this case, dial 999 immediately to request an ambulance.

Helping someone with hypothermia

While waiting for medical help, it's important to try to prevent further heat loss and gently warm the person. Follow these steps:

  • move the person indoors or somewhere warm as soon as possible
  • once they're somewhere warm, carefully remove any wet clothing and dry them
  • wrap them in blankets, towels or coats

If the person is unconscious, not breathing and you can't detect a pulse in their neck after 60 seconds, cardiopulmonary resuscitation (CPR) should be given if you know how to do it. Once CPR is started, it should be continued without any breaks until medical assistance arrives.

After the person is transferred to hospital, advanced medical treatments, such as removing blood from the body, heating it and returning it to the body, can be used to warm the person up.

Read more about treating 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 Payment for older people living alone who are vulnerable to hypothermia.

Read more about preventing hypothermia.

Page last reviewed: 20/04/2015

Next review due: 20/04/2017