Introduction

Hypothermia is a dangerous drop in body temperature below 35C (95F). Normal body temperature is around 37C (98.6F).

Hypothermia can be serious if not treated quickly. You should call 999 and give first aid if you notice signs of hypothermia.

Symptoms of hypothermia

Early signs of hypothermia include:

  • shivering
  • cold and pale skin
  • slurred speech
  • fast breathing
  • tiredness
  • confusion

There are symptoms of mild hypothermia, where someone's body temperature is between 32C and 35C.

If their temperature drops to 32C or lower, they'll usually stop shivering completely and may pass out.

This is a sign that their condition is getting worse and emergency medical help is needed.

Hypothermia in babies

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

Treating hypothermia

You should call 999 and then give first aid if you think someone's got hypothermia.

First aid for hypothermia

You need to warm the person up.

Follow these five steps:

  1. Move them indoors.
  2. Remove any wet clothing and dry them.
  3. Wrap them in blankets.
  4. Give them a warm non-alcoholic drink, but only if they can swallow normally.
  5. Give energy food that contains sugar, such as a chocolate bar, but only if they can swallow normally.

If the person can't be moved indoors, find something for them to rest on to protect them from the cold ground, like a towel or a blanket.

If they don't appear to be breathing - and you know how to do it - give them CPR, but you must continue this until professional help arrives in the form of the ambulance service or a medical team.

Things to avoid

Some things can make hypothermia worse:

  • Don't put the person into a hot bath.
  • Don't massage their limbs.
  • Don't use heating lamps.
  • Don't give them alcohol to drink.

These actions can cause the heart to suddenly stop beating (cardiac arrest).

Causes of hypothermia

Hypothermia happens when your body gets too cold and your temperature drops below 35C.

Hypothermia can be caused by:

  • inadequate clothing in cold weather
  • falling into cold water
  • getting cold in wet clothes
  • living in a cold house
  • being very tired and cold

Who's at risk?

Some groups of people are more vulnerable to hypothermia.

They include:

  • babies and children - they lose heat faster than adults
  • older people who are inactive and don't eat well
  • heavy alcohol and drug users - their bodies lose heat faster

Preventing hypothermia

To stay warm indoors in cold weather:

  • keep your home at a temperature of at least 18C
  • a baby's room should be 16-20C
  • keep windows and internal doors shut
  • wear warm clothes
  • use a room thermometer

Check in on an elderly neighbour regularly during cold weather to make sure their home is warm.

The government offers a Winter Fuel Payment for older people to help them pay their heating bills.

To stay warm outdoors:

  • plan your activity
  • plan for the unexpected
  • dress for the weather conditions
  • bring extra layers in case the weather changes
  • change out of wet or sweaty clothes as soon as possible
  • have non-alcoholic warm drinks
  • make sure you're never too far away from help
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Symptoms

The symptoms of hypothermia can vary depending on how low your body temperature has become.

The early symptoms of hypothermia are often recognised by a parent or carer. This is because it can cause confusion, poor judgement and changes in behaviour, which means the affected person may not realise they have it.

Mild hypothermia

If someone has mild hypothermia (generally with a body temperature of 32-35ºC), the symptoms aren't always obvious, but they can include:

  • constant shivering
  • tiredness
  • low energy
  • cold or pale skin
  • fast breathing (hyperventilation)

Moderate hypothermia

Moderate cases of hypothermia (generally with a body temperature of 28-32ºC) can include symptoms such as:

  • being unable to think or pay attention
  • confusion
  • loss of judgement and reasoning (someone with hypothermia may decide to remove clothing despite being very cold)
  • difficulty moving around
  • loss of co-ordination
  • drowsiness
  • slurred speech
  • slow, shallow breathing (hypoventilation)

People with a body temperature of 32ºC or lower will usually stop shivering completely. This is a sign that their condition is deteriorating and emergency medical help is required.

Severe hypothermia

The symptoms of severe hypothermia (a body temperature of below 28ºC) can include:

  • unconsciousness
  • shallow or no breathing
  • a weak, irregular pulse, or no pulse
  • dilated pupils

Someone with severe hypothermia may appear to be dead. However, under these circumstances they must be taken to hospital to determine whether they've died or if they're in a state of severe hypothermia. Medical treatment can still be used to resuscitate people with severe hypothermia, although it's not always successful.

Hypothermia in babies

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

When to seek medical attention

Seek medical attention as soon as possible if you suspect hypothermia.

If you suspect someone has severe hypothermia, dial 999 immediately to request an ambulance.

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Causes

Hypothermia is caused by getting too cold as the body loses more heat than it can generate and the body temperature drops below 35°C (95°F).

There are different types of hypothermia depending on how quickly the body loses heat.

  • acute or immersion hypothermia, which happens when a person loses heat very rapidly – for example, after falling into cold water
  • exhaustion hypothermia – this happens when a person’s body is so tired it can no longer generate heat
  • chronic hypothermia – heat is lost slowly over time; this is common in elderly people who live in poorly heated accommodation or in people sleeping rough

Hypothermia is most common in cold environments. You're more at risk if you don't wear enough layers to keep warm or you don't cover your head (a large amount of body heat is lost through your head).

It's also possible to get hypothermia in mild weather. For example, if you're soaked in the rain and don't dry off properly soon afterwards (particularly if there is a cool wind), the water evaporates from your skin and lowers your body temperature.

Who's at risk?

Certain groups, described below, have an increased risk of getting hypothermia because they're vulnerable to cold environments or they're unable to keep warm.

  • Babies can lose heat quickly if they're left in a cold room because they can't regulate their body temperature as well as older children and adults. Newborn babies in particular are at risk for the first 12 hours of their life.
  • Older people, particularly if they're not very active, do not eat enough, have other illnesses or take medication that can interfere with the body's ability to regulate temperature.
  • Homeless people who are unable to find shelter.
  • Heavy drug and/or alcohol users – these substances affect the body's ability to retain heat. The blood vessels stay widened (dilated), allowing heat to escape.
  • People with a condition that affects their memory, such as Alzheimer's disease, may not be able to recognise the symptoms of hypothermia or recognise when they're cold.
  • People with certain health conditions, such as heart problems, severe arthritis or someone who has had a stroke. These conditions can change the body's ability to respond to temperature changes – for example, by affecting the fingers and toes (where you may first feel cold).
  • People taking sedatives, which can interfere with the body's ability to regulate temperature.
  • People who spend long periods of time in cold weather conditions, such as climbers, walkers and skiers.
  • People who have suffered severe injury, particularly a head injury.

Read more about preventing hypothermia.

Perioperative hypothermia

It is also sometimes possible for hypothermia to occur during a stay in hospital - particularly before, during and after an operation. This is known as perioperative hypothermia.

Hospital staff will try to ensure you stay warm during your stay in hospital. They will monitor your temperature and may use a special blanket into which warm air is blown to help stop you getting too cold. This is called ‘forced air warming’.

You should tell staff if you feel cold at any time during your stay in hospital.

Read the National Institute for Health and Care Excellence (NICE) guidelines for more information about the management of inadvertent perioperative hypothermia in adults (PDF, 174kb).

Therapeutic hypothermia

In some cases, hypothermia is induced deliberately as a treatment. This is known as therapeutic hypothermia. There's evidence to suggest that, in some circumstances, inducing a state of hypothermia in the body can reduce the risk of death and increase the chances of a good recovery.

This group of people includes those who have suffered a cardiac arrest due to a heart attack outside of hospital, but who have been successfully resuscitated and are in an intensive care unit.

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Treatment

Hypothermia is treated by preventing further heat being lost and by gently warming the patient.

You should seek immediate medical attention if you suspect someone has hypothermia as it can be life threatening.

Read more about the symptoms of hypothermia.

Treating mild or moderate hypothermia

If you're waiting for medical treatment to arrive, the advice below will help prevent further heat loss.

  • Move the person indoors or somewhere warm as soon as possible.
  • Once the person is in a warm environment, carefully remove any wet clothing and dry them.
  • Wrap them in warm blankets, towels, or coats (whatever you have available), protecting their head and torso first.
  • Encourage the person to shiver if they're capable of doing so.
  • If possible, give the person warm drinks (not alcohol) or high-energy foods, such as chocolate, to help warm them up. But only do this if they can swallow normally – ask them to cough to see if they can swallow.
  • Once the person's body temperature has increased, keep them warm and dry.

It's important to handle a person with hypothermia gently and carefully.

Things to avoid

There are certain things you shouldn't do when helping someone with hypothermia because it may make the condition worse:

  • don't put the cold person into a hot bath
  • don't massage their limbs
  • don't use heating lamps
  • don't give them alcohol to drink

Trying to warm someone up yourself with hot water, massages, heat pads and heat lamps can cause the blood vessels in the arms and legs to open up too quickly.

If this happens, it can lead to a dramatic fall in blood pressure to the vital organs such as the brain, heart, lungs and kidneys, potentially resulting in cardiac arrest and death.

Severe hypothermia

If someone you know has been exposed to the cold and they're distressed or confused, they have slow, shallow breathing or they're unconscious, they may have severe hypothermia. Their skin may look healthy but feel cold. Babies may also be limp, unusually quiet and refuse to feed.

Cases of severe hypothermia require urgent medical treatment in hospital. You should call 999 to request an ambulance if you suspect someone has severe hypothermia.

As the body temperature drops, shivering will stop completely. The heart rate will slow and a person will gradually lose consciousness. They won't appear to have a pulse or be breathing. If you know how to do it, cardiopulmonary resuscitation (CPR) should be given while you wait for help to arrive.

Medical treatment

If someone is admitted to hospital with severe hypothermia, advanced medical treatment can be used to warm them up.

This can be done by temporarily withdrawing blood from the body, warming it and then returning it to the body. These techniques are cardiopulmonary bypass (sometimes called heart-lung bypass) and extra corporeal membranous oxygenation (ECMO).

However, these techniques are only available in major hospitals that have specialist emergency services or units that regularly perform heart surgery.

A person with severe hypothermia often stands a better chance of surviving if they're taken directly by ambulance to one of these hospitals, even if it means bypassing a smaller hospital along the way.

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Prevention

There are simple measures you can take to prevent you, your child or elderly relatives getting hypothermia.

Staying warm inside

Keep an eye on elderly or ill neighbours and relatives to ensure they're keeping their house warm during cold weather. The government offers a Winter Fuel Payment for older people living alone who are at risk of getting hypothermia. Keeping windows and internal doors closed will also help trap heat.

Use a room thermometer to ensure your house is at the right temperature. If you have reduced mobility, are 65 and over, or have a health condition such as heart or lung disease, the Department of Health recommends heating your home to at least 18ºC (64.4ºF).

If you're under the age of 65, active, and wearing appropriate clothing, you may wish to heat your home to a temperature at which you're comfortable, even if it's slightly lower than 18ºC.

If you have a baby, keep the room they sleep in at 16-20ºC (61-68ºF). This will help avoid sudden infant death syndrome (SIDS).

A healthy diet with plenty of fluids, warm drinks and regular meals can help provide energy so your body can generate heat. Avoiding alcohol, caffeine and smoking can also help as they all increase the rate at which the body loses heat.

If you're ill, visit your local pharmacy or GP to ensure you're treated promptly and effectively. Read about getting an annual flu vaccination. If you're taking regular medication, ask whether it affects your body's ability to regulate temperature.

The Keep Well this Winter Campaign is a Welsh Government initiative that is coordinated by Age Cymru and supported by a range of national organisations.

Staying warm outside

Make sure you're prepared for cold weather by checking the forecast and weather warnings on the Met Office website.

Wear appropriate warm clothing in cold weather and make sure your children are well wrapped up when outdoors. A significant amount of body heat can be lost through the head, even if the rest of the body is covered up, so you and your children should wear a warm hat.

Multiple thin layers of clothing trap air, which keeps you warm more effectively than one thick layer. Waterproof and windproof clothing gives the best protection outdoors in the sort of weather conditions found in the UK.

Eating and drinking regularly and having warm drinks – but not alcohol and caffeine – can also help keep you warm outside.

Keep active when it's cold, but not to the point where you're sweating. If you exercise outdoors during the winter and you sweat after exercising, make sure you dry off and put on warm clothes immediately afterwards. Wet clothes lose around 90% of their insulating power.

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The information on this page has been adapted by NHS Wales from original content supplied by NHS Choices.
Last Updated: 21/02/2018 11:00:00