Hypothermia occurs in cold environments when the normal body temperature of 37°C (98.6°F) drops below 35° (95°F). It can also happen due to prolonged exposure, rain, wind, sweat or being under cold water.

The usual response to getting too cold is to increase activity, however, if exposure continues then the body’s own automatic defence mechanisms will attempt to preserve further heat loss by:

• involuntary shivering to ensure major organs stay at normal temperature;
• restricting blood flow to the skin, and
• releasing hormones to generate heat.

These responses are usually inadequate to protect the body and they also drain energy reserves. It is when body energy is exhausted that hypothermia becomes potentially life-threatening.

Without treatment people with hypothermia can rapidly become very ill, lose consciousness and die. There is also an increased risk of stroke or heart attack due to blood clots forming.

It is important to treat the signs of hypothermia as a medical emergency, and to judge the symptoms rather than what a person says about their own condition. Hypothermia kills people every year - older people especially may not notice that their body temp has fallen, their rooms are too cold, or they can’t move about very well.

Symptoms

Symptoms vary depending upon the severity and length of exposure to cold. Mild:

• shivering,
• feeling cold,
• low energy,
• reduction in normal endurance, and
• cold red skin.

Moderate:

• violent shivering,
• inability to think or pay attention to events,
• confusion, so people may not know they are affected,
• loss of judgement and reasoning,
• poor movement, stumbling,
• feeling fearful,
• memory loss,
• fumbling hands,
• drowsiness,
• slurred speech,
• apathy, listlessness, indifference, and
• slow, shallow breathing and weak pulse.

Severe:

• loss of control of hands, feet, and limbs,
• shivering stops,
• unconsciousness,
• shallow or no breathing, and
• weak, irregular or no pulse.

Causes

Hypothermia is caused by getting too cold. Certain groups are at particular risk from getting hypothermic such as: 

• older people,
• homeless people, 
• babies under 12 months in cold bedrooms, 
• people recovering from accidents,
• people with other conditions, for example, mental health problems, heart problems, hypothyroid, on sedatives, alcoholism,
• people on medication, and
• people who expose themselves to extreme weather conditions eg climbers, walkers, skiers.

Treatment

Contact emergency services and get urgent medical assistance. However if medical care is not possible:· 

• find shelter, 
• insulate to prevent further heat loss,
• change out of wet clothing,
• warm the centre of the body first by whatever method you can to protect major body organs eg using an emergency blanket (‘space blanket’), your own body heat, skin-to-skin contact, or dry layers of blankets, clothing, towels, or layers of sheets, 
• give warm drinks (but no alcohol), and
• when the temperature increases keep dry and warm.