What is hypothermia?

Hypothermia happens when your body's temperature drops from a healthy range (usually around 37°C) to below 35°C. A drop in body temperature to 32°C or lower can be life-threatening.

Your body has several ways to warm up, if you are in a cold environment. You will start shivering, breathing faster and your muscles with tense. Your hairs will stand up straight (goosebumps) to trap warm air around you. Your heart will pump blood faster, but keep it away from your skin, especially your toes and fingers, to try and keep your core temperature higher.

When your body loses heat faster than your body can warm up, your core temperature will decrease, and you will be at risk of hypothermia.

How is hypothermia diagnosed?

Hypothermia is generally diagnosed based on symptoms and situational factors. It can also be determined using a special thermometer to measure your core body temperature.

A core body temperature is between 32 - 35°C is considered mild hypothermia.

A core body temperature below 32°C is considered severe hypothermia that can be life-threatening.

What are symptoms of hypothermia?

People with mild hypothermia have cold, pale skin. They may also be:

• shivering uncontrollably
• weak
• clumsy or uncoordinated
• confused and drowsy

People with severe hypothermia might have stopped shivering. They might:

• breathe slowly
• have a slow heart rate and a weak pulse
• have dilated pupils
• have stiff muscles
• have reduced consciousness or be in a coma

As their core body temperature continues to drop, they may lose consciousness and their heart may go into cardiac arrest.

Hypothermia can progress slowly, and the person may not realise that they need medical attention.

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What causes hypothermia?

You may develop hypothermia if you are exposed to cold conditions, such as air below 10°C or in water below 20°C. for a prolonged period. You can develop hypothermia whether you are outdoors or indoors if the conditions are cold enough.

What can make me more likely to get hypothermia?

You are at a greater risk of hypothermia if you are:

• an older person
• babies and young children
• underweight, nutritionally deficient, or have low body fat
• in poor general health
• under the influence of alcohol, sedatives or other drugs
• wet from any cause

Some medical conditions can mean people are more likely to get hypothermia, even in warmer environments. This may be because they are losing more heat than usual, have problems with the systems that help retain body heat or central nervous system problems.

These include conditions such as:

• burns or trauma to the skin
• any underlying infection or sepsis
• immobility or inactivity
• stroke
• diabetes
• poor blood circulation
• dementia

How is hypothermia treated?

If you suspect someone has hypothermia, you should follow the DRSABCD action plan. If you are worried, call triple zero (000) and ask for an ambulance. Keep checking them and stay with them until the ambulance arrives.

If they are conscious and have mild hypothermia:

• Move them to somewhere warm and dry, if it is safe to do so.
• Help them lay down and avoid excess movements.
• Take off any wet clothes.
• Warm their head, neck, chest and groin with blankets or wrapped hot water bottles, or use body to body contact.
• Keep them still.
• Give them warm drinks. Do not give them alcohol.

Don't make them move too much. Don't use direct heat (such as hot water or putting them in a hot bath). Don't rub their skin vigorously.

If someone's body temperature is below normal, it's important not to raise their body temperature too quickly by using direct heat. Sudden changes in body temperature can lead to shock. Medical professionals will aim to increase someone's body temperature gradually by 1to 2°C per hour.

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What are the complications of hypothermia?

Untreated, hypothermia can cause complications such as atrial fibrillation (abnormal heartbeat) and even cardiac arrest.

How can hypothermia be prevented?

Here are some tips to reduce your risk of hypothermia:

• Check the weather forecast.
• Limit the amount of time you spend outdoors in the cold.
• Plan 'warm-up' breaks if you work or spend a lot of time outside in cold weather.
• Dress warmly, including wearing a wind or water-resistant jacket, gloves and a hat.
• Stay dry and change out of wet clothes quickly.
• Avoid alcohol, caffeine and cigarettes, which can make you more sensitive to cold.
• Ask your doctor if your medicines could make you more susceptible to cold.

Young children and babies can lose body heat more quickly than adults because they have less muscle mass. Limit their exposure to extreme cold weather. Make sure you cover their heads when they are outside in the cold weather.

Read more on dressing your baby in cold weather.

Resources and support

• It's important to know how to stay safe and avoid hypothermia if you fall into cold water. Read about what to do at the NSW Government page on cold water and hypothermia.
• You can take a St John Ambulance Australia first aid course and learn how to treat hypothermia and save a life. You can also follow their hypothermia fact sheet for quick advice.