Hypothermia happens when the body temperature falls below a safe level, and it can be fatal. Infants and older people are especially at risk.

Under healthy conditions, the body maintains a relatively stable temperature of around 98.6˚F or 37˚C.

If the environment gets too cold or the body is unable to produce sufficient heat, the core temperature can drop, and hypothermia can develop.

Between 2003 and 2013, more than 13,400 people died from hypothermia in the United States, according to the .

Treatment depends on the degree of hypothermia, but the aim will be to make the person warm.

Treatments include the following:

First aid treatment

Anyone with symptoms of hypothermia will need immediate medical assistance.

Until medical assistance arrives, taking the following action can help:

It is vital not to use direct heat, such as heat lamps or hot water, as this can damage the skin. It can also trigger irregular heartbeats and, potentially, lead to cardiac arrest.

Do not rub or massage the person either, as these potentially jarring movements could also cause cardiac arrest.

Clinical treatment

According to published in the American Family Physician (AFP), the journal of the American Academy of Family Physicians (AAFP), the following techniques can help treat hypothermia.

Passive external rewarming: This uses the individual's heat-generating ability. It involves removing their cold, wet clothing, ideally replacing it with adequately insulated, dry clothing, and moving them to a warm environment.

Active external rewarming: This involves applying warming devices, such as hot-water bottles or warmed forced air, externally to truncal areas of the body. For example, the individual could hold a hot-water bottle under each arm.

Active core rewarming: This uses warmed, intravenous fluids to irrigate body cavities, including the thorax, peritoneum, stomach, and bladder. Other options include getting the individual to inhale warm, humidified air, or applying extracorporeal rewarming by using a heart-lung machine.

Do if they have signs of hypothermia, and avoid giving any drinks to an unconscious person.

A person with severe hypothermia may not seem to have a pulse or be breathing. If they appear to be dead, the bystanders to give CPR while keeping the person warm and waiting for emergency help. It is possible that this may resuscitate them.

Hypothermia generally progresses in three stages from mild to moderate and then severe.

According to the , the signs and symptoms of these stages are as follows:

StageBody temperatureSigns and symptoms
Mild90°F to 95°F (32.2°C to 35°C)High blood pressure, shivering, rapid breathing and heart rate, constricted blood vessels, apathy and fatigue, impaired judgment, and lack of coordination.
Moderate82.4°F to 90°F (28°C to 32.2°C)Irregular heartbeat, a slower heart rate and breathing, lower level of consciousness, dilated pupils, low blood pressure, and a decrease in reflexes.
SevereLess than 82.4°F (28°C)Labored breathing, nonreactive pupils, heart failure, pulmonary edema, and cardiac arrest.

Additional symptoms of hypothermia may include:

Mild:

Moderate to severe:

When a person has severe hypothermia, they may no longer know what they are doing, due to a .

Paradoxical undressing

Back in 1979, described a phenomenon known as paradoxical undressing.

In paradoxical undressing, people remove their clothes despite the cold. As a result of doing this, they lose more body heat, which can be fatal. This can happen during the later stages of hypothermia as the person becomes disoriented, confused, and possibly combative.

Although there is a lack of research on this situation, anecdotal evidence suggests that of deaths from hypothermia are due to paradoxical undressing.

In infants

Infants lose body heat more easily than adults, and they cannot shiver to keep warm.

Infants with hypothermia may have:

Infants should not sleep in a cold room. Using extra blankets is not a solution as there is a risk that these can smother the infant.

The making alternative arrangements if it is not possible to maintain a warm space where an infant can sleep.

Understanding and being prepared for hypothermia is integral to its prevention.

People are at higher risk if they:

At home

To prevent hypothermia indoors, the recommend the following:

Stranded in a motor vehicle

Anyone who becomes stranded in a motor vehicle should move everything they need from the trunk into the vehicle.

They should run the car for 10 minutes every hour, making sure that snow is not covering the exhaust pipe and keeping the window open a crack to prevent a buildup of fumes.

People should also consider creating a winter survival kit to keep in the car. The kit should contain nonperishable food, blankets, a first aid kit, water, and necessary medications.

Outdoor activities

Check the weather conditions before going out and dress appropriately.

Tips for avoiding hypothermia when outdoors include:

Overexertion will not help, as this can lead to exhaustion and result in sweat-drenched clothing, both of which contribute to heat loss.

A person who begins to experience or show signs of mild hypothermia should retreat to a warmer place immediately to prevent progression to a life-threatening condition.

Other tips

Other tips for a cold environment include:

Hypothermia in summer

Hypothermia can happen in summer too. Excessively cool air-conditioning or water-based activities pose a risk, especially for infants and older people who may not be able to express how they are feeling.

The recommend keeping room temperatures at 68°F (20°C) or above and closing off rooms that are not in use.

Hypothermia can result from a chronically cold environment, such as during winter, or it can happen suddenly, for example, if a person falls into cold water.

The that temperatures do not have to be excessively cold for hypothermia to develop. If the air temperature is 40°F (4.4°C) and a person is wet, they can develop hypothermia.

Hypothermia in water

People lose heat more quickly in water than on land. Water temperatures that would be comfortable as outdoor air temperatures can lead to hypothermia.

According to published in Scientific American, people in water that is 41°F (5°C) can lose muscle strength and coordination in as little as 10 minutes.

Even at 79°F (26°C), a person spending an extended period in the water may be at risk of hypothermia.

Indoor causes

Indoors, a lack of heating, excessive air conditioning or taking an ice bath can result in hypothermia.

Indoor hypothermia often has a poor outcome, because it tends to affect older people, and the diagnosis often comes at a late stage.

Vulnerable populations

Results of published in 2018 showed that 75 percent of people who received medical treatment in New York City hospitals for cold-related illness were outdoors when this happened.

Around half were sleeping rough, and another 25 percent had no heating at home. Substance abuse or having a mental or physical health condition increased the risk.

Most of the deaths and illnesses did not occur during periods of extreme cold.

The researchers noted, "Although the climate is warming, cold exposure is an ongoing concern during the winter."

Medical causes

Other causes of hypothermia include metabolic disorders that result in a lower basal metabolic rate. These disorders cause the body to generate less heat internally.

toxins and dysfunction of the thyroid, adrenal, or pituitary glands may also be underlying causes.