Treating hypothermia in the wilderness starts with one priority: stop the heat loss before you try to add heat back. Most of what you can do in a remote setting comes down to insulation, shelter, gentle handling, and knowing when someone needs evacuation. The approach changes significantly depending on whether the person is still shivering or has stopped, so recognizing the stage of hypothermia is your first step.
Recognizing the Stage
Hypothermia is loosely grouped into mild and severe, and in the field you won’t have a thermometer that reads core temperature. Instead, you’re reading behavior. A person with mild hypothermia (core temperature roughly 90 to 95°F) is alert, still shivering, but not functioning normally. They may fumble with zippers, stumble on flat ground, or seem confused. The important thing: they’re conscious and shivering. Shivering is the body’s most powerful rewarming tool, generating significant heat on its own.
Once shivering stops and mental status deteriorates, you’re dealing with moderate to severe hypothermia. The person may be semiconscious or unconscious, with a core temperature below roughly 82 to 90°F. At this point, the body can no longer rewarm itself, and the heart becomes electrically unstable. Dangerous heart rhythms can develop at core temperatures around 86°F and become increasingly likely below 72°F. This distinction between “still shivering” and “no longer shivering” drives every decision you make next.
Mild Hypothermia: Field-Treatable
If the person is alert, shivering, and able to protect their own airway (meaning they can swallow without choking), you can often treat them entirely in the field without evacuation. The Wilderness Medical Society guidelines confirm that patients with mild symptoms who respond to field treatment don’t need hospital transport. Here’s how to do it.
First, get them out of the wind and rain. A tent, a snow trench, a dense stand of trees, or even a group of people forming a windbreak all reduce convective heat loss. Remove wet clothing and replace it with dry layers. If you don’t have dry clothes, wring out what they’re wearing as thoroughly as possible and add insulation over it.
Let them shiver. Don’t try to suppress it. Shivering is doing the heavy lifting of rewarming, but it burns through the body’s fuel stores quickly. Feed them high-carbohydrate foods and fluids. The caloric content matters more than the temperature of the drink. Warm liquids feel comforting and add a small amount of heat, but sugar and carbohydrates are what actually fuel continued shivering. Avoid anything hot enough to burn the mouth or throat. Good options: sweetened warm water, hot cocoa, candy, granola bars, or anything carb-dense you have on hand.
Add external insulation generously. Place the person in a sleeping bag, pile extra clothing or packs around them, and put an insulating layer beneath them. Ground contact is a major source of heat loss that people overlook. A foam sleeping pad, a pile of pine boughs, or even an empty backpack under the torso makes a real difference.
Building a Hypothermia Wrap
For someone who can’t rewarm through shivering alone, or as a precaution for anyone you’re treating, a hypothermia wrap (sometimes called a “hypo wrap” or “burrito wrap”) is the gold standard of field insulation. It creates multiple layers that trap heat and block wind, rain, and evaporation.
Start by laying out a tarp or large plastic sheet on the ground. Place a sleeping pad on top of the tarp, then open a sleeping bag on top of the pad. Before placing the person inside the sleeping bag, wrap them in a vapor barrier: a plastic sheet, garbage bags, or even a rain jacket worn backward. This layer stops evaporative heat loss from damp skin and clothing, which can drain warmth surprisingly fast. Then zip the sleeping bag around them.
If you have chemical heat packs, place them on the center of the chest, with a layer of fabric between the heat source and bare skin to prevent burns. The chest is the most effective location because it warms the blood flowing through the heart and lungs. Avoid placing heat packs on the arms and legs (more on why below).
Now fold the tarp over the whole package. Start from the feet and work upward, folding snugly. If you have cord or webbing, lace it up the outside to keep everything tight. Leave the face open so they can breathe, creating a hood effect around the head. The goal is a sealed, windproof, waterproof cocoon with the person insulated on all sides, including beneath them.
Why Gentle Handling Matters
A severely hypothermic heart is electrically irritable. Rough jostling, sudden position changes, or even letting someone stand up and walk can trigger ventricular fibrillation, a lethal heart rhythm. People pulled from cold water are at especially high risk. If you suspect moderate or severe hypothermia, keep the person horizontal and handle them as gently as possible. Don’t let them sit up, stand, or exert themselves. Move them by carrying or dragging on an improvised sled, keeping their body level.
This also means you should avoid vigorous rubbing of the arms and legs, which is a common instinct but counterproductive. Beyond the cardiac risk, warming the limbs pushes cold blood from the extremities back toward the heart, which can actually cause core temperature to drop further. This phenomenon is called “afterdrop,” and it’s the reason you focus all rewarming efforts on the torso and core, not the hands and feet.
Severe Hypothermia: Stabilize and Evacuate
When someone has stopped shivering and is semiconscious or unconscious, they cannot rewarm themselves. Field treatment alone is not enough. Your job shifts from rewarming to preventing further heat loss and getting them to advanced medical care.
Build the hypothermia wrap described above. Add whatever heat sources you have to the torso. Protect them from the ground, wind, and precipitation. Then focus on evacuation. Patients with severe hypothermia need a hospital, ideally one with the ability to rewarm blood externally using specialized equipment. If you have any way to call for helicopter evacuation or search and rescue, do it early. Evacuation from the backcountry takes hours, and that clock starts when you make the call, not when you finish stabilizing the patient.
If the person appears to have no pulse and isn’t breathing, the decision to start CPR in the wilderness is complicated. Cold slows the heart dramatically, and a faint pulse may be undetectable with cold fingers in a windy environment. Check for breathing and a pulse for at least 60 seconds before deciding. If you do start CPR, you may need to continue it for a very long time. There are documented cases of people surviving prolonged hypothermic cardiac arrest with full neurological recovery, so the old adage in wilderness medicine holds: “nobody is dead until they’re warm and dead.”
Common Mistakes to Avoid
- Warming the extremities first. Putting someone’s hands in warm water or wrapping heat packs around their arms drives cold blood to the core, worsening afterdrop. Focus heat on the chest and torso.
- Giving food or drink to someone who isn’t fully alert. If the person can’t sit up and swallow reliably, they risk choking or aspirating fluid into their lungs. Only feed people who are conscious, alert, and able to protect their own airway.
- Letting them walk it off. Exercise generates heat, but it also circulates cold peripheral blood and puts stress on an irritable heart. Keep moderate-to-severe hypothermia patients still and horizontal.
- Underestimating wet clothing. Water conducts heat away from the body roughly 25 times faster than air. Even slightly damp base layers continue pulling heat. Prioritize getting wet fabric off the skin or at least adding a vapor barrier over it.
- Skipping ground insulation. People focus on piling blankets on top and forget that the cold ground underneath is a massive heat sink. Always insulate below the person first.
Gear That Makes a Difference
If you’re heading into cold backcountry, a few lightweight items dramatically improve your ability to treat hypothermia. A compact emergency bivy or space blanket works as a vapor barrier. Chemical heat packs weigh almost nothing and provide hours of warmth applied to the chest. A foam sleeping pad is non-negotiable ground insulation. Carry a lighter or fire-starting kit, because a fire provides radiant heat, dries clothing, and boosts morale in a survival situation.
A thermometer that reads below 95°F is useful but not essential. In the field, you’ll rely on mental status and shivering to classify severity. The most important “gear” is the knowledge to act quickly: shelter first, insulate from the ground up, wrap the core, feed the shivering patient, handle the non-shivering patient like glass, and call for help early when someone stops being able to rewarm themselves.