Hypothermia: What Shivering Tells You, and When It Stops

A person who is shivering hard in the cold is miserable, but in one important sense they are doing well. Shivering is the body making heat. It is the main defence against cooling, and a person who can still shiver strongly, talk sensibly and move normally is usually in the mildest stage of hypothermia, where warming them up is straightforward.

The dangerous moment is when the shivering stops and the person is still cold. MyHealth Alberta notes that shivering may stop once body temperature drops below about 32 °C. To a bystander this can look like improvement: the person has settled down and gone quiet. It is often the opposite. The body has run out of the ability to fight, and the cooling is now happening faster.

This post explains how to read a cold person using what you can see, without a thermometer, and why the care changes so much between a shivering, talking person and a quiet, drowsy one. It is not a substitute for hands-on training, and it does not certify you in anything.

Reading a cold person without a thermometer

In the field you almost never know a person's core temperature. An ordinary thermometer in the mouth or ear reads the surface, not the core, and gives false comfort in the cold. What you can judge reliably is how the person is behaving. Canadian first aid teaching looks at four things together: how responsive the person is, how well they move, whether they are shivering, and how alert they are.

The picture below is a general guide, not a set of hard lines. People move between stages, and a person with other injuries, who has been drinking, or who is very old or very young may not follow the pattern neatly.

Why gentle handling matters

A very cold heart is irritable. As hypothermia deepens, rough handling or sudden movement can tip it into a rhythm that does not pump blood. This is why people who seemed alive when they were found have sometimes collapsed during a rescue, and why the Wilderness Medical Society's hypothermia guideline stresses handling a hypothermic person gently and keeping them horizontal.

In practice that means once a person is past the mild stage, do not make them walk, do not rub their arms and legs, and do not jostle them. Move them only as much as you need to get them out of the wind and off the cold ground, and lift and carry them flat if you can. Rubbing the limbs is a particularly common instinct and it does nothing useful: it does not warm the core, and it sends cold blood from the arms and legs back toward the heart.

A person who is mildly hypothermic, shivering and thinking clearly can walk to a warmer place. It is the drowsy, confused or non-shivering person who needs to be kept still. a wilderness first aid course built around long waits for help.

Stop the heat loss first

Whatever the stage, the first job is to stop the person getting any colder. Most heat is lost to wind, to wet clothing and to the cold ground underneath them, and in the field those matter more than any heat source you can add.

The order matters less than doing all of it quickly. A person lying in the snow in a good jacket is still losing heat into the ground through their back. what frostbite does to fingers and toes, and how to warm them.

Then add heat, carefully

For a mildly hypothermic person who is shivering, alert and able to swallow safely, food and warm sweet drinks help a lot. Shivering burns energy fast, and giving the body fuel keeps it shivering. MyHealth Alberta advises warm fluids and food, and avoiding alcohol and caffeine. Alcohol in particular makes people feel warmer while making them lose heat faster.

Heat packs or warm water bottles help, but put them where the core will benefit: the chest, the armpits and the back, wrapped so they never sit directly on skin. Cold skin burns easily. Sharing body heat inside a sleeping bag or blanket with a warm person is another option.

MyHealth Alberta advises against a warm water bath. Putting a cold person into hot water can drop their blood pressure and cause collapse. Leave warm baths out of it, especially for anyone past the mild stage.

A person who is drowsy, confused or not shivering should not be given anything to eat or drink, because they may not be able to swallow safely. Insulate, warm the core gently, and get professional help moving.

When to call 911, and CPR in the cold

Call 911 for anyone who is confused, drowsy, not shivering while still cold, has slow or shallow breathing, or cannot be woken. MyHealth Alberta lists stumbling, weakness, confusion, extreme sleepiness, slow shallow breathing and a slow or uneven pulse among the severe symptoms that need emergency help now.

A severely hypothermic person can look dead when they are not. Breathing can be very slow and shallow, and the pulse very hard to find. This is the one situation where the usual ten-second breathing check is too short: in a very cold person, watch and listen for up to a minute before deciding. If the person is unresponsive and not breathing normally, call 911 and start CPR as you would for anyone else.

Hypothermic people have survived long resuscitations that would be hopeless at normal body temperature, because cold slows the brain's need for oxygen. That is a reason to start and keep going, not a reason to stop. The decision about when to stop belongs to the paramedics and the hospital, not the first person on scene. the 80-hour Advanced First Aid course for industrial responders.