Hypothermia

Hypothermia is dangerously low body temperature, below 95°F (35°C).

Other types of cold injuries that affect the limbs are called peripheral cold injuries. Of these, frostbite is the most common freezing injury. Nonfreezing injuries that occur from exposure to cold wet conditions include trench foot and immersion foot conditions. Chilblains (also known as pernio) are small, itchy or painful lumps on the skin that often occur on the fingers, ears, or toes. They are a type of nonfreezing injury that develops in cold, dry conditions.

You are more likely to develop hypothermia if you are:

• Very old or very young
• Chronically ill, especially people who have heart or blood flow problems
• Malnourished
• Overly tired
• Taking certain prescription medicines
• Under the influence of alcohol or drugs

Hypothermia occurs when more heat is lost than the body can make. In most cases, it occurs after long periods in the cold.

Common causes include:

• Being outside without enough protective clothing, especially in winter
• Falling into cold water of a lake, river, or other body of water
• Wearing wet clothing in windy or cold weather
• Heavy exertion, not drinking enough fluids, or not eating enough in cold weather

As a person develops hypothermia, they slowly lose the ability to think and move. In fact, they may even be unaware that they need emergency treatment. Someone with hypothermia also is likely to have frostbite.

The symptoms include:

• Confusion
• Drowsiness
• Pale and cold skin
• Slowed breathing or heart rate
• Shivering that cannot be controlled (although at extremely low body temperatures, shivering may stop)
• Weakness and loss of coordination

Lethargy (weakness and sleepiness), cardiac arrest, shock, and coma can set in without prompt treatment. Hypothermia can be fatal.

Call 911 or the local emergency number anytime you suspect someone has hypothermia. Give first aid while waiting for emergency help.

Before you spend time outside in the cold, do not drink alcohol or smoke. Drink plenty of fluids and get enough food and rest.

Wear proper clothing in cold temperatures to protect your body. These include:

• Mittens (not gloves)
• Wind-proof, water-resistant, many-layered clothing
• Two pairs of socks (avoid cotton)
• Scarf and hat that cover the ears (to avoid major heat loss through the top of your head)

Avoid:

• Extremely cold temperatures, especially with high winds
• Wet clothes
• Poor circulation, which is more likely from age, tight clothing or boots, cramped positions, fatigue, certain medicines, smoking, and alcohol

Prendergast HM, Erickson TB. Procedures pertaining to hypothermia and hyperthermia. In: Roberts JR, Custalow CB, Thomsen TW, eds. Roberts and Hedges' Clinical Procedures in Emergency Medicine and Acute Care. 7th ed. Philadelphia, PA: Elsevier; 2019:chap 65.

Sawka MN, O'Connor FG. Disorders due to heat and cold. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 95.

Zafren K, Danzl DF. Hypothermia, frostbite, and nonfreezing cold injuries. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 128.

Last reviewed on: 11/2/2023

Jesse Borke, MD, CPE, FAAEM, FACEP, Attending Physician at Kaiser Permanente, Orange County, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.