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What is Hypothermia (Low Core Body Temperature)? Signs & Symptoms

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Hypothermia is the medical term for a low core body temperature (below 35 degrees Celsius/95 degrees Farenheit) due to the failure of the body to maintain its normal temperature (thermoregulation). Mild hypothermia is a body temperature between 35 and 32 degrees Celsius. Severe hypothermia is when your body temperature drops below 32 degrees Celsius.

The body’s core temperature is monitored and maintained by the hypothalamus at around 37.5 degrees Celsius. In hypothermia, the body is either unable to restore its normal body temperature due to impaired thermoregulatory mechanisms or the environmental temperature is extremely low where even normal thermoregulation cannot cope. The patient may be unable to hold a thermometer in the mouth, so a rectal temperature should be taken.

Signs and Symptoms of Hypothermia

Stage One

The first signs and symptoms of hypothermia may be noticed when the body temperature drops below 36.5 degrees Celsius yet its above 35 degrees Celsius. At this stage the heart rate may increase above 100 beats per minute (tachycardia) and there are signs of reduced blood flow to the skin and periphery (pale skin/pallor or light blue tinge of the fingers and toes in anemic patients).

Stage Two – Mild Hypothermia

As the core body temperature drops further, below 35 degrees Celsius (mild hypothermia), other more serious igns and symptoms may be evident. This includes :

  • Skin feels colder than normal but may still be lukewarm.
  • Shivering.
  • Dehydration.
  • Mental confusion.
  • Poor coordination of voluntary movements (ataxia) – slurred speech, stumbling, clumsiness.

Stage Three – Severe Hypothermia

When the core body temperature drops below 32 degrees Celsius, there are more serious signs and symptoms and the hypothermia may be irreversible in some situations.

  • Skin cold to touch.
  • No shivering.
  • Reduced consciousness.
  • Low blood pressure (hypothermia).
  • Heart rate below 60 beats per minute (bradycardia).
  • Weak pulse.
  • Shallow breathing.
  • Muscle stiffness.
  • Abnormal ECG readings.

As the core body temperature drops below 28 degrees Celsius, a person may be mistaken for being dead.

  • Coma.
  • Absent pupil reflexes.
  • Faint pulse that may be difficult to detect.
  • Shallow breathing that may be barely detectable.

Article reviewed by Dr. Greg. Last updated on June 11, 2010