Hypothermia sets in when your core body temperature drops below 95°F (35°C), and the right response depends on how far it has fallen. The most important thing you can do is get the person out of the cold, call emergency services, and begin gentle rewarming of the chest and torso, not the arms and legs. Acting quickly matters, but so does avoiding common mistakes that can make things worse.
Recognizing the Three Stages
Knowing which stage someone is in helps you judge how urgently they need professional medical care and how carefully you need to handle them.
Mild (95°F to 89.6°F): The body is still fighting back. You’ll see shivering, chattering teeth, clumsiness, slow reactions, and exhaustion. The person may seem unusually sleepy and have a weak or rapid pulse. This stage is the most treatable in the field.
Moderate (89.6°F to 82.4°F): Shivering may slow or become irregular. Breathing and heart rate drop. Speech becomes slurred, mental function declines, and the person may lose consciousness. This is a medical emergency.
Severe (below 82.4°F): Shivering stops entirely. Blood pressure falls dangerously low, and fluid can build up in the lungs. The heart becomes extremely vulnerable to irregular rhythms. At this point, the person may appear dead but can still sometimes be resuscitated. The old saying in emergency medicine is “nobody is dead until they’re warm and dead.”
First Aid Steps in Order
Call 911 or your local emergency number immediately for anything beyond mild hypothermia, or for mild hypothermia that isn’t improving. While you wait, or if you’re in a remote setting, follow these steps:
- Get out of the cold. Move the person to shelter, even a car or a makeshift windbreak. If you can’t move them, shield them from wind and insulate them from the ground. Cold ground pulls heat from the body fast.
- Remove wet clothing. Wet fabric accelerates heat loss dramatically. Replace it with dry layers, blankets, or whatever you have.
- Warm the center of the body first. Focus heat on the chest, neck, head, and groin. Use skin-to-skin contact under blankets, warm (not hot) compresses, or chemical heat packs wrapped in cloth. Hot water bottles placed under the arms and at the groin are especially effective.
- Offer warm drinks if the person is conscious and alert. Warm, sweet, non-alcoholic fluids help gently raise core temperature from the inside.
- Handle the person gently. Rough movement can trigger a dangerous heart rhythm in someone with moderate or severe hypothermia. Keep them horizontal if possible.
The Wilderness “Burrito Wrap”
If you’re far from medical help, a technique used by mountain rescue teams can significantly slow heat loss and begin rewarming. Lay a tarp flat on the ground. Stack one or two sleeping pads on top (two is always better, since ground contact is a major source of heat loss). Place up to three sleeping bags on the pads, then put the person inside the middle bag.
Tuck hot water bottles under the arms, at the groin, and at the feet if you have extras. Then wrap the tarp around everything like a burrito, sealing the person inside layers of insulation with a vapor barrier on the outside. This setup traps body heat while the hot water bottles provide external warmth to the areas where major blood vessels run close to the skin.
What Not to Do
Some of the most intuitive responses to hypothermia are actually dangerous. Warming someone too quickly, such as putting them in a hot bath or using a heating lamp, can cause a potentially fatal drop in blood pressure. It can also trigger something called afterdrop, where cold blood from the limbs rushes back to the heart and causes core temperature to plunge even further before it starts to rise. Research on afterdrop shows that when shivering is suppressed, core temperature can continue falling by more than 1°C after rewarming begins, and recovery can take four times longer.
Massaging or heating the arms and legs is specifically contraindicated. Warming the extremities opens up blood vessels there, which sends cold blood back to the core and puts stress on the heart and lungs. Let the body rewarm from the center outward.
Don’t give alcohol. It feels warming because it opens blood vessels near the skin, but that actually accelerates heat loss and slows the rewarming process. Tobacco products also interfere with circulation needed for recovery. And don’t let the person “walk it off.” Physical exertion pushes cold blood from the muscles toward the heart and can cause cardiac arrest in moderate to severe cases.
What Happens at the Hospital
For mild to moderate hypothermia with stable circulation, hospitals use heated blankets, forced-air warming devices, and warmed intravenous fluids (typically heated to 100°F to 108°F). These approaches gently raise core temperature in a controlled way.
Severe hypothermia with an unstable heartbeat requires more aggressive intervention. Doctors may use body-cavity lavage, where warm fluid is circulated through the chest or abdomen to heat the organs directly. In the most extreme cases, a machine called ECMO can take over the work of the heart and lungs, warming the blood outside the body before returning it. This technology has saved people who arrived at the hospital with no detectable pulse.
Controlled rewarming in a hospital setting typically happens at a rate of about 0.25°C to 0.5°C per hour. Faster rewarming risks secondary injury, particularly to the brain. This is why the field goal is simply to prevent further heat loss and begin gentle core warming while getting the person to definitive care.
Hypothermia in Infants
Babies lose heat much faster than adults because of their higher surface-area-to-body-weight ratio and limited ability to shiver. The signs also look different. Instead of the shivering and slurred speech you’d see in an adult, a hypothermic infant may be excessively sleepy, unusually irritable, feeding poorly with a weak suck, or showing mottled or pale skin with cold hands and feet.
In very young infants under 60 days old, hypothermia may be the only visible sign of a serious infection, because their immune systems don’t always produce a fever in response. A cold baby who seems lethargic or is feeding poorly needs medical evaluation, not just extra blankets. Hold the baby against your skin under a warm covering while you seek help.
Who Is Most at Risk
Hypothermia doesn’t require arctic conditions. It can happen at temperatures well above freezing, especially with wind, rain, or water immersion. Older adults with reduced circulation or less body fat are particularly vulnerable, as are people who are intoxicated, exhausted, or dehydrated. Homeless individuals, hikers caught in unexpected weather, and anyone immersed in cold water face elevated risk. Water pulls heat from the body roughly 25 times faster than air at the same temperature.
Indoor hypothermia is more common than most people realize, particularly among elderly people living in poorly heated homes. If someone you know seems confused, unusually clumsy, or excessively sleepy in a cold environment, check for hypothermia even if you’re indoors.