What Causes Hypothermia?

What is Hypothermia?

Normal human body temperature is 98.6 degrees Fahrenheit, or 37 degrees Celsius. The body is able to maintain this temperature by balancing heat production with heat loss.

Cellular metabolic processes produce heat, which dissipates via convection, conduction, and evaporation, through mechanisms such as sweating and panting.

The body produces more heat in cold environments, and uses bodily mechanisms such as shivering to generate even more heat when required. Sometimes, heat loss is so great that the body cannot maintain its normal temperature. When this happens, core body temperature begins to drop. Body heat is diverted from the skin and extremities to the brain, heart, and other organs to ensure they have enough warmth to function.

The definition of hypothermia is a core body temperature of less than 95 degrees Fahrenheit, or 35 degrees Celsius. If the body cannot retain normal core temperature and continues to lose heat, eventually organs will begin to fail, and death may result.

What Causes Hypothermia?

The most common cause of hypothermia is exposure to cold temperature. This may be because an individual finds themselves in worse weather than expected, or because he or she is inadequately clothed for the weather conditions.

The process of hypothermia is hastened if the individual is partially or fully immersed in water. Just a few minutes of immersion in cold water can potentially be fatal.

Several factors can increase the risk of developing hypothermia.

  • Children and older people may not be able to generate enough heat to maintain normal core body temperature.
  • People with certain diseases such as Parkinson’s disease and hypothyroidism, which reduce the body’s ability to correctly regulate its core temperature.
  • People whose mental function or judgment is impaired by disease, medication, or substance abuse.
  • Substance abuse can also increase the risk because alcohol and certain other drugs dilate blood vessels located near the skin, meaning the body is less able to retain heat.
  • Several types of medical conditions can increase the risk. Circulatory conditions, including diabetes, as well as spinal cord injuries, can make the shivering mechanism less effective. Someone who has a brain tumor or has had a stroke may be less able to regulate core body temperature.


Benjamin C. Wedro, MD, FAAEM for MedicineNet.com: Hypothermia

The Mayo Clinic on Hypothermia

University of Maryland Medical Center: Hypothermia