Hypothermia is a condition involving a low body temperature, usually below 95°F (35°C). Shivering, pale skin, unclear speech, and a fast heart rate can be signs of hypothermia. It is a medical emergency.

The stages of hypothermia range from mild to severe. Even the mild stage is an emergency, and a bystander should call 911 if they notice its signs. While waiting on help to arrive, first aid treatment entails getting the individual to a warm, dry place and removing any wet clothing.

The underlying cause of hypothermia is prolonged exposure to cold. That said, other factors and conditions can increase the risk, including extremes in age and certain health conditions, such as malnutrition.

Keep reading to learn more about the treatment, symptoms, prevention, diagnosis, and causes of hypothermia.

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Hypothermia is an abnormally low body temperature of below 95°F (35°C). This happens when a person experiences cold temperatures for a prolonged period.

While normal metabolic processes in the body generate heat, wintry weather can cause the body to lose more heat than it generates. When this occurs, the core temperature drops.

A structure in the brain called the hypothalamus regulates body temperature. Findings show that when someone is exposed to cold, the hypothalamus raises body temperature through measures such as increasing muscle tone and shivering.

However, if exposure to cold continues, it will eventually overwhelm the body, and shivering will stop. At this point, multiple organs may stop functioning, which ultimately leads to death. This is why hypothermia is an extremely dangerous condition.

Symptoms in babies differ from symptoms in adults, note the Centers for Disease Control and Prevention (CDC). Babies may have very low energy and bright red, cold skin.

As hypothermia progresses through the stages, symptoms become more severe and dangerous. A 2021 review article describes the symptoms in adults as follows:

Mild hypothermia

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Symptoms in this stage include:

  • body temperature of 90–95°F (32–35°C)
  • tiredness
  • shivering
  • hunger
  • nausea
  • skin that is dry and paler than usual
  • fast heart rate
  • increased muscle tone
  • increased blood pressure
  • decline in memory, judgment, and thinking ability
  • unclear speech
  • loss of control of body movements
  • frequent urination

Moderate hypothermia

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Typically, shivering stops between 86–90°F (30–32°C). Other symptoms of moderate hypothermia include:

  • body temperature of 82–90°F (28–32°C)
  • continued decline in thinking ability
  • lethargy
  • enlarged and less responsive pupils
  • low blood pressure
  • slow heart rate
  • slow breathing rate
  • paradoxical undressing, or removal of clothes
  • increased susceptibility to abnormal heart rhythms

Severe hypothermia

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Symptoms of this stage include:

  • body temperature of less than 82°F (28°C)
  • continued decline in blood flow to the brain, leading to unresponsiveness
  • continued decline in blood pressure, heart rate, and heart output
  • increased susceptibility to abnormal heart rhythms
  • congestion in lungs
  • production of a very small amount of urine
  • loss of reflexes
  • ultimately, failure of heart and lung function

Treatment depends on the degree of hypothermia, but the aim is to make the person warmer. It involves first aid and clinical treatment.

First aid

Anyone with symptoms of hypothermia needs immediate medical attention. Until help arrives, the CDC recommends:

  • moving the person to a warm, dry place, if possible, or sheltering them from the elements
  • taking off any wet clothing
  • covering the person with an electric blanket, if available, or dry layers of towels, clothing, or blankets
  • making skin-to-skin contact with another individual
  • having the person drink a warm beverage, excluding alcohol, if they are not unconscious
  • avoiding moving or jostling the person, as doing so can trigger a fatal heart rhythm abnormality

If someone has severe hypothermia, they may be unconscious. They may also appear not to have a pulse or be breathing. If this occurs, a bystander should perform CPR and continue it until help arrives. Sometimes people with hypothermia who appear to be dead can resuscitate.

Clinical treatment

Research states that clinical treatment may include the following options:

  • Passive external rewarming: This entails removing the person’s wet clothing and covering them with layers of insulation.
  • Active external rewarming: This involves methods such as water immersion and using a heating unit to transfer heat through convection. However, water immersion poses the danger of triggering collapse of the heart and blood vessels.
  • Active core rewarming: This involves irrigating body cavities with warm, intravenous fluids. Other options include the use of warming that originates from outside the body, such as hemodialysis, which is filtering of the blood with a machine that acts as an artificial kidney.

A 2018 study provides the following prevention recommendations:

  • Check the weather forecast before going outdoors, and dress appropriately.
  • Avoid drinking alcoholic and caffeinated beverages, as they increase heat loss.
  • Wear multiple layers of clothing, including a hat, scarf, and gloves.
  • Set the home thermostat to 68°F (20°C) or higher, and dress warmly.
  • Keep space heaters, which are an acceptable indoor heat source, away from flammable objects and ensure smoke and carbon monoxide detectors work.
  • Place rolled towels underneath home doors to prevent drafts.
  • Check on elderly neighbors, and make sure they have enough heat and food.
  • Dress babies warmly, and limit their exposure to cold temperatures.

In winter, unexpected events can occur that pose a danger of hypothermia, such as home power outages and running out of gas while driving. To offset the risk of these events, experts recommend keeping winter survival kits at home and in the car.

Certain medications, specifically psychiatric medications, may increase a person’s risk of hypothermia. An individual may consider asking their doctor or pharmacist whether their medication could increase their risk of hypothermia.

Home survival kits may include:

  • extra food and water
  • an emergency heating source
  • a fire extinguisher and smoke detector

Car survival kits may include:

  • sleeping bags and blankets
  • high calorie, nonperishable food
  • extra clothing to keep dry
  • water container
  • waterproof matches

When doctors examine a person, the key symptoms and signs below indicate a diagnosis of hypothermia:

  • body temperature below 95°F (35°C)
  • shivering
  • impaired mental state
  • frostbite, which is injury to body tissues resulting from freezing

Other telltale symptoms inlude:

  • frequent urination
  • fast heart rate, fast breathing, and high blood pressure in mild hypothermia
  • slow heart rate, slow breathing, and low blood pressure in moderate hypothermia
  • a long pause in breathing or coma in severe hypothermia

Evidence shows that the diagnostic process should also include blood tests to measure:

  • blood sugar
  • electrolytes, such as sodium and potassium
  • substances that show kidney function

Doctors may order an electrocardiogram (ECG) to assess heart function. They may also use imaging tests, such as X-rays, to assess the effects of a stroke or trauma that led to prolonged exposure to cold. Additionally, a doctor may use other lab studies and tests to detect potential complications and underlying causes of hypothermia.

Exposure to cold temperatures or falling into cold water can cause hypothermia.

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

Certain factors or conditions can make an individual more susceptible to hypothermia. These include:

  • extremes of age
  • low blood sugar
  • malnutrition
  • skin disorders, such as burns and psoriasis
  • stroke
  • endocrine disorders, such as hypothyroidism and adrenal insufficiency, which are conditions affecting parts of the body that produce hormones
  • substance use disorder
  • neurodegenerative disorders, such as dementia
  • dilated blood vessels due to conditions such as spinal cord injuries
  • sepsis, which is an extreme response to infection

Doctors diagnose hypothermia if a person’s body temperature falls below 95°F (35°C). Shivering, impaired thinking ability, and frostbite are also key indications of the condition.

When spending time in cold environments, someone may not have access to a thermometer to take their temperature. With this in mind, it helps to be familiar with the symptoms of hypothermia. Even mild symptoms indicate the need for immediate medical attention.

Employing prevention measures, such as checking the weather forecast before going out, can reduce the likelihood of hypothermia. Keeping a winter survival kit in the home and the car could enable people to survive prolonged exposure to cold.