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.

Symptoms Causes Risk factors Complications Prevention

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.

Mild hypothermia

Signs and symptoms of mild hypothermia include:

  • Shivering
  • Dizziness
  • Hunger
  • Nausea
  • Faster breathing
  • Trouble speaking
  • Slight confusion
  • Lack of coordination
  • Fatigue
  • 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.

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