Causes and Risk Factors of Hypothermia

Understanding How Hypothermia Happens

Hypothermia can be a medical emergency or a lifesaving medical intervention; it just depends on the context. Accidental hypothermia is caused by environmental factors including cold weather, cold water immersion, and also surgery. Therapeutic hypothermia is used to slow metabolic actions in certain situations to give the body time to heal before more damage is done.

hypothermia causes
Illustration by Joshua Seong. © Verywell, 2018. 

Common Causes

Exposure to cold air or cold water is the biggest cause of hypothermia. Surprisingly, it doesn't take extremely cold weather to cause it. The only thing that matters is how cold the body gets. Chatting in the parking lot on a cool night with no coat is enough to reach mild hypothermia if you stand out there long enough. Indeed, the problem with hypothermia is that it creeps up on you.

If the weather isn't too cold, the body can stave off hypothermia by creating its own heat. The most obvious way the body does that is by shivering, although there are other metabolic processes using fat that create heat and help avoid hypothermia.

Mild hypothermia is often not reported or treated on temperate nights because when a patient reaches his tolerance level, he usually goes inside where it's warm and all is good. A little wind or a little water, however, can make it much worse. An incident in the Philippines demonstrates that even in the tropics, enough wind and rain can cause hypothermia.

Cold Water Immersion

The fastest cause of hypothermia is immersion in cold water. Water conducts heat away from the body much more quickly than air. Falling into cold water is well known as a medical emergency.

Climbing out of the water with soaked clothes is also a problem. The wet clothing against skin continues to pull heat away. One of the first steps in treating hypothermia is to remove wet clothing, even if it means the patient gets naked. A thin, dry blanket is better than a couple of layers of wet clothing.

However, one study found that falling in the water while clothed might be better. There is a layer of water next to the skin that acts as a thermal layer, trapping heat until the patient starts moving or trying to swim. Researchers were attempting to determine whether or not waiting for help is better than swimming to safety in cold water immersion. As it turns out, falling in with clothes on keeps the patient warmer, but trying to swim out with clothes on is more dangerous due to fatigue.

Wind Chill Factor

A convection oven cooks faster and more evenly by moving air across the roasting turkey. Cold winds work the same way in reverse. Cold air blowing across the body removes heat faster.

Wind chill isn't just a trick of the body feeling as if the air is colder; it actually accelerates loss of heat from the body and hastens hypothermia.


The environment isn't always about the weather. Patients in surgical situations can develop hypothermia for two reasons. First, they're naked. Typically, surgical patients don't have much more than a blanket or two to keep them warm in a room often kept cooler than the average home.

Second, their guts are exposed. Skin works as a permeable insulation to keep heat in the body.

When the skin is cut open and the outside air is cooler than body temperature, the internal organs are exposed to outside air and the body is cooled very quickly.

Therapeutic Hypothermia

Not all causes of hypothermia are bad. Therapeutic hypothermia is a medical treatment modality intended to slow down metabolism in order to let healing catch up. Therapeutic hypothermia is mostly used after cardiac arrest resuscitation.


Body fat, specifically brown fat, acts as both insulation and heat generator. Fat levels are often determined by genetic profile. Certain native populations have evolved adaptations to cold weather, such as metabolic adaptations of Native Americans that lead to higher metabolic rates and a higher core body temperature.

Cardiovascular Risk Factors

Patients with metabolic disorders like diabetes are more prone to hypothermia than other populations. Likewise, some patients with neurological disorders have trouble regulating core body temperatures.

If you know that you are at higher risk because of these circumstances, be mindful of common hypothermia causes so that you can take preventive measures.

Alcohol as a Risk Factor

The use of alcohol is one of the biggest risk factors that can cause hypothermia.

Alcohol is a vasodilator, meaning that it opens up peripheral blood vessels and allows blood to flow freely to the surface of the skin. That blood flow puts patients with alcohol in their bloodstream at risk for hypothermia while at the same time feeling as if they are nice and warm.

Alcohol makes you feel as if you are warm by moving all that nice, warm blood closer to the temperature receptors located in the skin. Alcohol has such a reputation for warming you up that it is often touted as an elixir against the cold. Hot Toddy's are sold at nearly every ski lodge, luckily right next to the fireplace.

Unfortunately, blood so close to the surface allows more heat to escape the bloodstream and, ultimately, the body. Even though a drink or two may make you feel warm in the moment, you are now much more susceptible to hypothermia.

Frequently Asked Questions

  • What are the stages of hypothermia?

    Medical experts typically recognize three stages of hyporthermia, based on core body temperature and symptoms:

    • Mild: 90 to 95 degrees; shivering and alert; altered mental state
    • Moderate: 82 to 90 degrees; decreased level of consciousness; shivering or no longer shivering
    • Severe: Under 82 degrees; unconscious; no longer shivering

    Some also regard core body temperatures under 68 degrees or 75 degrees as profound hypothermia.

  • How can I tell if someone is hypothermic?

    When core body temperature drops below normal, a person will start shivering, become extremely tired and drowsy, and show signs of mental impairment, such as slurred speech, fumbling hands, confusion, and memory loss.

  • What medications can increase the risk of hypothermia?

    Certain drugs can impair the body's mechanisms for regulating body temperature, impair a person's ability to recognize the sensation of being cold, and/or cloud their judgment. Medications that can increase the risk of hypothermia include:

  • What should I do for someone who's showing signs of hypothermia?

    Start by taking their temperature. If it's below 95 degrees, get them to an emergency room immediately or call 911 for help. If you have to wait for medical attention, take steps to bring up the person's body temperature, such as moving them to a warmer area and applying layers of dry blankets, bedding, blankets, and/or clothing.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Gocotano AE, Dico FD, Calungsod NR, Hall JL, Counahan ML. Exposure to cold weather during a mass gathering in the Philippines. Bull World Health Organ. 2015;93(11):810-4. doi:10.2471/BLT.15.158089

  2. Centers for Disease Control and Prevention. Prevent hypothermia & frostbite.

  3. Bowes, H., Eglin, C., Tipton, M., & Barwood, M. (2016). Swim performance and thermoregulatory effects of wearing clothing in a simulated cold-water survival situation. European Journal Of Applied Physiology116(4), 759-767. doi:10.1007/s00421-015-3306-6

  4. Bilgin H. Inadverdent Perioperative Hypothermia. Turk J Anaesthesiol Reanim. 2017;45(3):124-126. doi:10.5152/TJAR.2017.200501

  5. Schenone AL, Cohen A, Patarroyo G, et al. Therapeutic hypothermia after cardiac arrest: A systematic review/meta-analysis exploring the impact of expanded criteria and targeted temperature. Resuscitation. 2016;108:102-110. doi:10.1016/j.resuscitation.2016.07.238

  6. Nishimura, T., & Watanuki, S. (2014). Relationship between mitochondrial haplogroup and seasonal changes of physiological responses to cold. Journal Of Physiological Anthropology33(1), 27. doi:10.1186/1880-6805-33-27

  7. Centers for Disease Control and Prevention. Hypothermia-Related Deaths.

  8. Klein, L., Cole, J., Driver, B., Battista, C., Jelinek, R., & Martel, M. (2018). Unsuspected Critical Illness Among Emergency Department Patients Presenting for Acute Alcohol Intoxication. Annals Of Emergency Medicine71(3), 279-288. doi:10.1016/j.annemergmed.2017.07.021

  9. UpToDate. Accidental hypothermia in adults.

Additional Reading
  • Fudge, J. (2016). Exercise in the Cold.Sports Health: A Multidisciplinary Approach8(2), 133-139. doi:10.1177/1941738116630542

By Rod Brouhard, EMT-P
Rod Brouhard is an emergency medical technician paramedic (EMT-P), journalist, educator, and advocate for emergency medical service providers and patients.