What Hypothermia Is, and Why It Matters
Hypothermia: what it is, why it matters, and what published guidance actually asks of you.
It can happen indoors as well as outdoors, and it affects thinking, so people may not realize it is happening.
Key takeaways
- Definition: body temperature below 95°F (35°C)
- Signs in adults: shivering, exhaustion, confusion, fumbling hands, memory loss, slurred speech, drowsiness
- Most useful single change: Dress in layers and cover your head, hands and feet in cold weather.
- Commonest mistake: Drinking alcohol to "warm up".
- See a doctor if any of the signs under "When to speak to a doctor" below apply to you.
The short answer
A dangerously low body temperature caused by losing heat faster than the body can produce it.
Where it fits
This is part of Weather Safety. The figures come first, because the advice only makes sense against them.
The numbers, in one place
| Measure | Figure |
|---|---|
| Definition | body temperature below 95°F (35°C) |
| Signs in adults | shivering, exhaustion, confusion, fumbling hands, memory loss, slurred speech, drowsiness |
| Signs in babies | bright red, cold skin and very low energy |
| Higher risk | older adults, babies, people who drink heavily and people outdoors for long periods |
| Can occur | even above 40°F (4°C) if a person is chilled by rain, sweat or cold water |
What that means in practice
Translated into things you can actually do:
- Dress in layers and cover your head, hands and feet in cold weather
- Change out of wet clothes as soon as possible
- Warm the center of the body first: chest, neck, head and groin
- Give warm, non-alcoholic drinks only if the person is fully alert
What gets people into trouble
The pitfalls worth knowing about:
- Drinking alcohol to "warm up"
- Warming the arms and legs before the center of the body
- Giving drinks to someone who is unconscious
Related topics
- CPR and Defibrillation: What the Evidence Actually Says (Emergency Care)
- Sun and Heat Abroad: What the Evidence Actually Says (Travel Health)
- Dry Skin: Sorting the Evidence From the Noise (Skin Health)
- The Evidence on Fever, Without the Hype (Immunity)
Where to go next
- Popular Beliefs About Hypothermia, and What Is Actually Published
- Hypothermia: A Beginner-Friendly Start
- Hypothermia — the reference entry
- Weather Safety: The Complete Guide
- Frostbite: What Published Guidance Supports
- Wildfire Smoke: What Published Guidance Supports
When to speak to a doctor
Call 911 if a person's temperature is below 95°F or they are confused, very drowsy or unresponsive. If the person has no pulse, start CPR while waiting for help.
Where this comes from
- CDC — Preventing Hypothermia
- National Institute on Aging — Cold Weather Safety for Older Adults
How this page was put together
Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.
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