Symptoms and Signs of Hypothermia

Medical Author:
Medically Reviewed on 11/18/2021

Doctor's Notes on Hypothermia

Hypothermia is defined as a core or internal body temperature (best measured with a rectal thermometer) of less than 95 F or 35 C. Signs and symptoms of hypothermia vary with the decreasing core temperature. Shivering, along with an increase in heart rate, breathing rate, and blood pressure are seen at a core temperature of about 95 F or somewhat below. As temperature decreases toward 89.9 F, heart rate, breathing rate, and blood pressure decrease and the person becomes clumsy, confused, apathetic, and develops slurred speech; below 89.9 F, the shivering and oxygen consumption drops while the person may develop an irregular heartbeat and may become stuporous. At core temperatures below 82.4 F, reflexes are lost, cardiac output falls, the chances of a dangerous heart rhythm increase, brain activity slows, and the patient appears comatose or dead. However, some patients can be revived. Almost all individuals with hypothermia should be evaluated by an emergency medical caregiver (call 911).

The cause of hypothermia is exposure to a cold or frigid environment long enough to not allow the body to sustain a normal core temperature (98 F-100 F). Cold water immersion can drop core temperatures to dangerous levels in minutes (falling through ice in a lake or river). It may take hours for hypothermia to develop in cold dry environments (homeless, elderly in an unheated house).

What Is the Treatment for Hypothermia?

Call 911, and begin first aid:

  • Gently handle the patient to avoid cardiac arrest.
  • Move patient to a warm and dry location.
  • Remove wet clothing.
  • Cover the patient with dry blankets.
  • If outside, insulate the patient from the cold ground.
  • Monitor breathing (may need CPR).
  • Apply warm, dry compresses only to the neck, chest wall, and groin -- do not apply the compresses to the extremities as this may cause a drop in core temperature that can be fatal.
  • Don't apply direct heat like hot water or a heat lamp to avoid irregular heartbeats.
  • Hospital medical treatment (depends on the severity) may include the following:
    • Cover the patient with heated blankets; if able, have the patient drink warm fluids.
    • Warm IV fluids
    • Airway rewarming
    • Catheter used to place warm saltwater around the lungs or the abdominal cavity
    • Blood rewarming by hemodialysis and/or heart bypass

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Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.