Hypothermia is a medical emergency that occurs when your body loses heat faster than it can produce heat, causing a dangerously low body temperature. Normal body temperature is around 98.6 F (37 C). Hypothermia (hi-poe-THUR-me-uh) occurs as your body temperature passes below 95 F (35 C).
When your body temperature drops, your heart, nervous system and other organs can’t work normally. Left untreated, hypothermia can eventually lead to complete failure of your heart and respiratory system and to death.
Hypothermia is most often caused by exposure to cold weather or immersion in a cold body of water. Primary treatments for hypothermia are methods to warm the body back to a normal temperature.
Hypothermia occurs when your body loses heat faster than it produces it. The most common causes of hypothermia are exposure to cold-weather conditions or cold water. But prolonged exposure to any environment colder than your body can lead to hypothermia if you aren’t dressed appropriately or can’t control the conditions.
Specific conditions leading to hypothermia include:
- Wearing clothes that aren’t warm enough for weather conditions
- Staying out in the cold too long
- Unable to get out of wet clothes or move to a warm, dry location
- Accidental falls in water, as in a boating accident
- Inadequate heating in the home, especially for older people and infants
- Air conditioning that is too cold, especially for older people and infants
How your body loses heat
The mechanisms of heat loss from your body include the following:
- Radiated heat. Most heat loss is due to heat radiated from unprotected surfaces of your body.
- Direct contact. If you’re in direct contact with something very cold, such as cold water or the cold ground, heat is conducted away from your body. Because water is very good at transferring heat from your body, body heat is lost much faster in cold water than in cold air. Similarly, heat loss from your body is much faster if your clothes are wet, as when you’re caught out in the rain.
- Wind. Wind removes body heat by carrying away the thin layer of warm air at the surface of your skin. A wind chill factor is important in causing heat loss.
Shivering is likely the first thing you’ll notice as the temperature starts to drop because it’s your body’s automatic defense against cold temperature — an attempt to warm itself.
Signs and symptoms of mild hypothermia include:
- Faster breathing
- Trouble speaking
- Slight confusion
- Lack of coordination
- Increased heart rate
Moderate to severe hypothermia
As your body temperature drops, signs and symptoms of moderate to severe hypothermia include:
- Shivering, although as hypothermia worsens, shivering stops
- Clumsiness or lack of coordination
- Slurred speech or mumbling
- Confusion and poor decision-making, such as trying to remove warm clothes
- Drowsiness or very low energy
- Lack of concern about one’s condition
- Progressive loss of consciousness
- Weak pulse
- Slow, shallow breathing
Someone with hypothermia usually isn’t aware of his or her condition because the symptoms often begin gradually. Also, the confused thinking associated with hypothermia prevents self-awareness. The confused thinking can also lead to risk-taking behavior.
Hypothermia in infants
Typical signs of hypothermia in an infant include:
- Bright red, cold skin
- Very low energy
- A weak cry
Hypothermia not necessarily related to the outdoors
Hypothermia isn’t always the result of exposure to extremely cold outdoor temperatures. An older person may develop mild hypothermia after prolonged exposure to indoor temperatures that would generally be fine for a younger or healthier adult. This can occur in a poorly heated home or in an air-conditioned home. Signs and symptoms of this type of hypothermia may not be as obvious.
When to see a doctor
Call 911 or your local emergency number if you see someone with signs of hypothermia or if you suspect a person has had unprotected or prolonged exposure to cold weather or water.
If possible take the person inside, moving them carefully and slowly. Jarring movements can trigger dangerous irregular heartbeats. Carefully remove wet clothing, and cover him or her in layers of blankets while you wait for emergency help to arrive.