Treating hypothermia correctly depends on how cold the person is, but the core principle is the same: rewarm slowly, handle gently, and avoid common mistakes that can make things worse. Hypothermia begins when core body temperature drops below 95°F (35°C), and the approach changes significantly as temperature falls further. Getting the basics right, especially in the first minutes, can be the difference between recovery and cardiac arrest.
How to Recognize the Stage
Hypothermia is classified into three stages based on core body temperature, and each stage calls for a different level of intervention.
Mild (90–95°F / 32–35°C): The person shivers, feels fatigued, and may seem confused or clumsy. Hunger, nausea, and pale skin are common. The body is still actively trying to generate heat, so blood pressure, heart rate, and breathing may all be elevated. Judgment and memory start to slip, and speech may become slurred.
Moderate (82–90°F / 28–32°C): Shivering typically stops once the core drops to around 86–90°F, which is actually a dangerous sign because it means the body has exhausted its ability to warm itself. The person becomes drowsy, reflexes slow, and pupils may dilate. Heart rhythm disturbances become more likely. A strange behavior called “paradoxical undressing” sometimes occurs at this stage, where the person removes clothing despite being dangerously cold.
Severe (below 82°F / 28°C): The person may be unresponsive. Blood pressure, heart rate, and breathing all continue to drop. The risk of fatal heart rhythms is high. Without intervention, this stage leads to cardiorespiratory failure.
Immediate First Aid Steps
The first priority is stopping further heat loss. Move the person out of the cold environment, or at minimum shield them from wind and wet ground. Remove any wet clothing and replace it with dry layers or blankets. This approach, called passive rewarming, works by letting the body’s own heat production gradually raise core temperature. For mild hypothermia, this alone is often enough.
If you have access to warm (not hot) drinks, offer them to a person who is alert and able to swallow. The calories help fuel the body’s heat-generating machinery. Place warm compresses or heat packs on the chest, neck, and groin, where large blood vessels sit close to the skin. Avoid placing heat directly on the arms and legs. Warming the extremities pushes cold blood from the limbs back toward the heart, which can trigger dangerous heart rhythms or cause core temperature to drop even further.
If the person is unconscious or not breathing, call emergency services immediately and begin CPR if you’re trained to do it. In hypothermia, a stiff body can mimic rigor mortis, but rigidity from cold is not a reliable sign of death. Resuscitation should continue until medical professionals take over.
Why Gentle Handling Matters
A hypothermic heart is electrically unstable. Rough movement, jostling, or even vigorous rubbing of the limbs can trigger ventricular fibrillation, a chaotic heart rhythm that stops effective blood flow. This is why every guideline stresses moving a hypothermic person as gently and horizontally as possible. Avoid letting them walk, stand, or exert themselves. Even well-intentioned actions like vigorously massaging someone’s arms to “warm them up” can stress the heart and lungs.
Keep the person lying down and move them only when necessary. If you need to transport them, keep movements smooth and minimize any jarring.
What Not to Do
Several common instincts actually make hypothermia worse:
- Don’t use a hot bath or heating lamp. Rewarming too quickly can cause a dangerous drop in blood pressure and trigger cardiac complications.
- Don’t warm the arms and legs directly. This forces cold peripheral blood back to the core, potentially lowering core temperature further and stressing the heart.
- Don’t give alcohol. It dilates blood vessels near the skin, which feels warm but actually accelerates heat loss from the core and hinders rewarming.
- Don’t offer cigarettes or tobacco. Nicotine constricts blood vessels and interferes with the circulation needed for recovery.
- Don’t rub or massage the limbs. Beyond the cardiac risk, frostbitten tissue can be permanently damaged by friction.
How Medical Rewarming Works
For moderate and severe hypothermia, passive rewarming alone isn’t sufficient. Medical teams use active rewarming techniques that fall into two categories.
Active external rewarming applies heat to the body’s surface. The most common method is forced-air warming, essentially a blanket connected to a device that blows warm air across the skin. Heated blankets, warming mattresses, and radiant warmers also fall into this category. These methods are effective for moderate hypothermia and help reduce a phenomenon called “afterdrop,” where core temperature continues to fall even after rescue because cold blood from the extremities returns to the heart.
Active internal rewarming is reserved for severe cases, especially when the heart has stopped. This involves warming the body from the inside using heated intravenous fluids (warmed to 98.6–106°F / 37–41°C), warm fluid irrigation of body cavities, or in the most extreme cases, running the blood through an external warming circuit. Administering room-temperature or cold fluids to a hypothermic person causes additional heat loss, so any intravenous fluids given during treatment are pre-warmed.
The Afterdrop Problem
One of the trickiest aspects of hypothermia treatment is afterdrop. Even after rewarming begins, core temperature can continue to fall. This happens because cold blood pooled in the arms, legs, and skin flows back toward the heart and internal organs, mixing with warmer core blood and dragging the overall temperature down.
Two mechanisms drive this. One is simple heat conduction through tissue as the body re-establishes thermal balance. The other is convective: circulating blood carries cold from the periphery to the core, especially when the person moves or is moved. This is one more reason to keep a hypothermic person still. Rescuers should expect that multiple afterdrops can occur whenever a patient is repositioned or transported. Active external warming helps counteract afterdrop by pre-warming the peripheral tissues so they draw less heat away from the core.
CPR and Cardiac Arrest in Hypothermia
Hypothermia slows metabolism so dramatically that the brain and organs can survive much longer without oxygen than they normally would. This is the basis for a well-known principle in emergency medicine: “no one is dead until they are warm and dead.” A person in hypothermic cardiac arrest may look lifeless, with fixed dilated pupils, no detectable pulse, and a rigid body, yet still be resuscitable.
CPR should not be withheld based on how long the person has been in cardiac arrest, how low their temperature is, their age, or even the presence of major trauma. The only reasons to stop or not begin CPR are clear signs of irreversible death (such as dependent lividity), a valid do-not-resuscitate order, danger to the rescuers, or an avalanche burial lasting longer than 60 minutes with a completely blocked airway and no heart activity. In all other cases, resuscitation continues while the person is rewarmed, sometimes for hours.
Recovery and What to Expect
For mild hypothermia caught early, recovery is usually straightforward. Passive rewarming with dry blankets, warm drinks, and shelter from the elements can bring core temperature back to normal within a few hours. Most people feel fatigued and cold for some time afterward but recover fully.
Moderate and severe cases require hospital care and carry real risks. Even moderate hypothermia (around 95°F) can impair blood clotting by disrupting platelet function, increasing bleeding risk. It also triggers the release of stress hormones that constrict blood vessels and raise blood pressure, which can reduce blood flow to the heart muscle. These effects are why hypothermia during surgery is associated with heart complications, wound healing problems, and longer hospital stays.
Rewarming in a medical setting typically proceeds at a controlled rate, generally 0.25–0.5°C (roughly 0.5–1°F) per hour for patients being brought back from targeted temperature management, though the rate varies by clinical situation. The slow pace helps avoid the cardiovascular instability that rapid rewarming can cause. Recovery from severe hypothermia, especially cases involving cardiac arrest, can be prolonged and may require intensive care for days.