Elderly patients, very young patients, patients with diabetes or circulatory problems, and patients with low body fat are more susceptible to hypothermia and its complications compared to the rest of the population.


In freezing temperatures, the body’s response to hypothermia also creates an increased risk for frostbite. Frostbite occurs when body tissues freeze and crystallize. The most distal parts of the body are most susceptible to frostbite (fingers, toes, nose, and earlobes). This is where it is hardest to flood tissues with a constant flow of warm blood.

In cold environments, the first compensatory mechanism a person’s body will use to reduce heat loss is to shunt blood away from the body’s surface. This has the undesirable effect of not warming those distal points. Freezing environmental temperatures will cause freezing in tissues without fresh, warm blood to counteract it.

It is possible to develop frostbite without developing hypothermia, but the presence of frostbite is an indicator that the environment is dangerously cold and hypothermia is possible.


Moderate/Severe Hypothermia

If left untreated, mild hypothermia could worsen and body temperature could drop below 90 degrees and becomes moderate hypothermia. Shivering stops as the body switches from using energy as a source of heat to conserving energy in the face of cold exposure.

Signs of Moderate to Severe Hypothermia

  • Absence of shivering
  • Dilated pupils
  • Confusion
  • Fatigue
  • Loss of consciousness

Once you become moderately hypothermic, the situation must be addressed, or you will continue to worsen and will develop severe hypothermia.

As the core body temperature drops below 83 degrees, you will most likely be unconscious and unresponsive to most stimuli. Often, deep tendon reflexes are diminished or absent, meaning that you will not respond to any attempts to be woken up.

Severe hypothermia is a serious medical emergency.

Patients with this stage of hypothermia are at an increased risk for sudden cardiac arrest due to the irritability of heart muscle tissues at lower temperatures. Even rewarming will require close monitoring in the event that the patient suffers a cardiac arrhythmia.


Mild Hypothermia

As the body cools, it will take steps to prevent the heat loss. The earliest signs of hypothermia occur when skin temperature (not core body temperature) falls below an average of about 95 degrees when measured over several areas of the body—what’s known as the mean skin temperature.

At this early stage, circulation to the skin is decreased, which keeps blood away from the cold surface of the body and helps to preserve core body temperature. The person might notice that fine motor skills (texting on a phone, for example) are getting harder to perform and they are beginning to shiver. Shivering comes from the body expending energy to create heat and is a coping mechanism for cold exposure.

Actual hypothermia occurs when the core body temperature falls below 95 degrees. Uncontrollable shivering is the first and most obvious sign of mild hypothermia.

Signs of Mild Hypothermia

  • Uncontrollable shivering
  • Social withdrawal, becoming quiet and non-communicative
  • Difficulty concentrating
  • Fumbling fingers. For example, having more than just trouble texting—now the patient might drop her phone.
  • Sense of discomfort or pain

If you are removed or protected from the cold environment (e.g. with blankets, dry clothes, hot cocoa), mild hypothermia can be reversed fairly easily. If not, the core body temperature is likely to continue to drop.


Signs and Symptoms of Hypothermia

The signs and symptoms of hypothermia are divided roughly by the severity of the hypothermia. There isn’t a universal definition of the categories of severity, but most healthcare providers use mild, moderate, and severe, defined by body temperature and associated signs.

Cold exposure can come on slowly, affecting someone before he or she realizes there’s a problem. If you’re not looking for the signs and symptoms of hypothermia, it can be easy to miss until the problem has become significant.

Suspicion of hypothermia is almost as important as recognizing the signs and symptoms. It’s just as important to recognize the conditions under which hypothermia can happen and pay close attention to the people exposed to those conditions, including yourself.


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.


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.


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.



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.


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.

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.

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.

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.3

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.


Causes and Risk Factors of Hypothermia

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.