Hypothermia sets in when your core body temperature drops below 35°C (95°F), and how you respond in the first minutes matters enormously. The priority is always the same: stop further heat loss, rewarm the core gradually, and handle the person gently. What you should not do is almost as important as what you should, because well-meaning mistakes like rubbing someone’s limbs or warming them too fast can trigger dangerous heart rhythms.
Recognizing the Stages
Hypothermia progresses through distinct stages, and knowing which one you’re dealing with shapes how aggressively you need to act.
Mild (32–35°C / 90–95°F): The body is still fighting. Shivering is intense, speech may be slurred, and coordination starts to slip. The person is usually conscious and can follow instructions. This stage is very treatable in the field.
Moderate (28–32°C / 82–90°F): Shivering slows or stops entirely, which is a bad sign, not a good one. It means the body has lost the ability to generate its own heat. Confusion deepens, drowsiness sets in, and the person may not recognize they’re in danger. The heart becomes increasingly irritable and vulnerable to abnormal rhythms.
Severe (below 28°C / 82°F): The person may be unconscious, with a weak or undetectable pulse and very slow, shallow breathing. Some patients appear dead. At this stage, rough handling or sudden movement can cause the heart to stop. Hospital care is essential.
First Aid for Mild Hypothermia
If someone is still shivering and alert, you can often reverse hypothermia without medical equipment. Move them out of the cold and wind, and get them off the ground. Cold ground conducts heat away from the body fast, so lay a blanket, sleeping pad, or even a backpack underneath them. Gently remove any wet clothing and replace it with dry layers or blankets.
Offer warm, sweet, nonalcoholic drinks. The warmth helps from the inside, and the sugar provides quick fuel for the body’s heat-generating machinery. Avoid alcohol entirely. It dilates blood vessels near the skin, which feels warm but actually accelerates core heat loss.
If the person can move safely, light physical activity like walking generates body heat. But this only applies to mild cases where the person is alert and coordinated enough to do so without risk of injury.
Handling Moderate to Severe Cases
Once shivering has stopped or the person is confused and drowsy, the situation is more serious and your approach needs to change. The single most important rule: be gentle. Rough movement, jostling, or letting the person sit upright can cause cold blood pooling in the limbs to rush back to the heart, potentially triggering a fatal heart rhythm. Keep the person horizontal at all times and move them as little as possible.
Focus rewarming on the center of the body only. Apply warm compresses, wrapped hot water bottles, or chemical heat packs to the neck, chest, and groin. Never try to warm the arms and legs. Heating or massaging the limbs stresses the heart and lungs and can worsen the situation. This is one of the most common and dangerous mistakes bystanders make.
If you’re using a hot water bottle or chemical pack, wrap it in a towel first. Hypothermic skin burns easily because blood flow to the surface is reduced, so the person may not feel a burn developing.
The Hypo-Wrap for Wilderness Situations
When you’re far from a hospital and need to stabilize someone, a hypo-wrap buys critical time. The technique layers insulation and a vapor barrier to trap whatever body heat remains and prevent evaporative cooling from wet skin or clothing.
Start by placing the person on an insulating layer on the ground, inside a vapor barrier like a plastic sheet or emergency bivvy. This barrier stops moisture from evaporating off the skin, which is a major source of heat loss that dry blankets alone won’t prevent. Then place them inside a sleeping bag and zip it up. Wrap the whole package in a tarp, securing it with cord from feet to neck in a daisy-chain pattern. Leave the top open as a hood, or close it over the head if rain or wind is a concern.
If you have a heat source like a chemical warmer, place it directly on the center of the chest inside the wrap. Don’t let it delay getting the person to help, and make sure it’s wrapped to prevent burns.
Understanding Afterdrop
One of the trickiest aspects of treating hypothermia is a phenomenon called afterdrop. Even after you begin rewarming someone, their core temperature can actually continue to fall. This happens because warming the skin and outer tissues causes blood vessels near the surface to relax and open up, allowing cold blood from the extremities to flow back into the central circulation.
Afterdrop can temporarily worsen the person’s condition and increase the risk of dangerous heart rhythms or cardiac arrest. This is why rewarming should focus on the core, not the limbs, and why gradual, gentle warming is safer than aggressive external heat. It’s also why someone who seems to be improving can suddenly deteriorate, so stay with them and monitor closely even after rewarming has started.
What Happens at the Hospital
For moderate and severe hypothermia, hospital treatment uses internal rewarming methods that work much faster than anything available in the field. These can include warmed fluids delivered directly into the bloodstream, heated fluid flushed through the abdominal cavity, and specialized rewarming tubes.
In the most severe cases, particularly when the heart has stopped, a machine that draws blood out of the body, warms and oxygenates it, and pumps it back in has become the gold standard for rewarming. This technology keeps organs supplied with oxygen-rich blood while gradually bringing the core temperature back up. Survival from hypothermic cardiac arrest is possible even after prolonged resuscitation, which is why emergency teams continue CPR far longer than they would for other causes of cardiac arrest. There’s a well-known principle in emergency medicine: a hypothermic patient is not considered dead until they are warm and dead.
Common Mistakes to Avoid
- Rubbing or massaging the limbs. This forces cold blood back toward the heart and can trigger cardiac arrest.
- Warming the extremities first. Always focus heat on the neck, chest, and groin. Warming arms and legs stresses the heart.
- Giving alcohol. It feels warming but opens blood vessels at the skin surface, increasing heat loss from the core.
- Letting the person stand or sit up. Vertical positioning drops blood pressure further in someone already compromised. Keep them lying flat.
- Moving them roughly. An irritable, cold heart can go into a lethal rhythm from sudden jolts or vigorous activity.
- Assuming someone is dead. Severe hypothermia can slow breathing and pulse to nearly undetectable levels. Check carefully for at least a full minute before concluding there’s no pulse.
Who Is Most at Risk
Hypothermia doesn’t require extreme cold. It can develop in temperatures well above freezing, especially when wind, wet clothing, or water immersion are involved. Older adults, young children, and people who are very thin or malnourished lose heat faster. Alcohol and certain drugs impair the body’s ability to regulate temperature and dull awareness of cold, making intoxicated people particularly vulnerable. Even healthy, well-equipped hikers can develop hypothermia if they get wet and can’t dry off, especially at higher elevations where wind and lower temperatures compound the problem.
Prevention comes down to staying dry, layering clothing, eating enough calories to fuel heat production, and drinking plenty of fluids. Dehydration impairs circulation, which makes it harder for the body to distribute warmth. If conditions turn against you, acting early while you’re still shivering and thinking clearly gives you the best chance of reversing the process before it progresses.