You're standing on a hiking trail or maybe just a cold parking lot, and your friend is shivering. It’s freezing out. You think, "They’re just cold." But then the shivering stops. That's actually the moment things get dangerous. People think hypothermia is this dramatic, cinematic event where someone turns into an ice cube, but it’s sneakier than that. Knowing when to call 911 for hypothermia isn't just about checking a thermometer; it's about watching how a person's brain and body are failing in real-time.
Hypothermia happens when your body loses heat faster than it can produce it. Once your core temperature drops below 95°F (35°C), your organs start to struggle. It doesn't even have to be "Arctic" cold. You can get hypothermia in 60-degree weather if you're wet and the wind is blowing.
The "Umbles" that mean you need emergency help
Most wilderness medics use a shortcut called the "umbles." If someone is stumbling, mumbling, fumbling, or grumbling, their brain is literally cooling down. This is the first major red flag.
When someone is in mild hypothermia, they shiver violently. That’s the body’s way of trying to kickstart the furnace. But as they move into moderate or severe territory, that shivering stops. If your friend was freezing and suddenly says they feel "fine" or "warm" while they're still in the cold, that is a medical emergency. You need to call 911 immediately. This is often called "paradoxical undressing" in extreme cases, where the victim feels like they are burning up and starts taking off their clothes. It sounds crazy, but it happens because the blood vessels that were constricted suddenly dilate, sending a rush of warm blood to the skin, tricking the brain into thinking the body is overheating.
Why the "Mumbles" are a 911 call
Slurred speech is a massive indicator. If someone sounds like they’ve had three stiff drinks but they haven't touched a drop of alcohol, their nervous system is slowing down. According to the Centers for Disease Control and Prevention (CDC), confusion and memory loss are primary symptoms that require professional intervention. You can't just "walk off" a cooled-down brain.
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When to call 911 for hypothermia: The definitive checklist
You should call for an ambulance the second you notice any of these specific shifts:
- The Shivering Stops: This is the most counterintuitive sign. If they were shivering and now they aren't, but they are still in a cold environment, their body has run out of fuel.
- Altered Mental Status: Any confusion, irritability, or "spaced out" look. If they can't tell you what day it is or where they are, call 911.
- Loss of Coordination: If they can't zip up their jacket or they’re walking like they’re on a boat in a storm.
- Low Energy: Extreme drowsiness or an inability to stay awake.
- Weak Pulse: If you're checking their wrist and the beat feels thready or very slow.
Honestly, if you're even asking yourself if you should call, the answer is usually yes. Hypothermia impairs judgment. This means the person who is actually dying from the cold will likely tell you they don't need help. They might even get angry if you suggest it. You have to be the one to make the call.
What to do while you wait for the sirens
Calling 911 is step one, but in remote areas or during a blizzard, help might be twenty minutes or two hours away. You have to be careful. You can't just throw someone into a hot shower or rub their arms and legs.
Dr. Gordon Giesbrecht, a world-renowned expert on cold-water immersion often called "Professor Popsicle," emphasizes that you must handle hypothermic patients extremely gently. Their hearts are highly irritable. If you jolt them or move them too roughly, you can actually trigger a fatal heart rhythm called ventricular fibrillation. Basically, the cold heart is like a delicate piece of glass.
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Move them out of the wind. If their clothes are wet, you have to get them off. Wet clothes pull heat away from the body 25 times faster than dry ones. Get them into dry layers or wrap them in a "burrito" of blankets. If you have chemical heat packs, put them on the chest, neck, and groin—not the arms or legs. Heating the limbs first can send cold blood back to the heart too quickly, which is a phenomenon called "afterdrop" that can cause the core temperature to plummet even further.
Misconceptions that can be fatal
A lot of people think a shot of whiskey will warm you up. It won't. Alcohol is a vasodilator. It opens up the blood vessels near the skin, which makes you feel warm but actually dumps your core heat into the environment even faster. It also prevents the shivering response. Don't give a hypothermic person booze.
Another mistake is trying to give them food or water if they aren't fully conscious. If they're "out of it," they can't swallow properly and might aspirate, leading to choking or pneumonia. If they are alert enough to swallow, warm, sweetened liquids are okay, but avoid caffeine.
High-risk groups you need to watch
The elderly and infants are at much higher risk. Babies lose heat quickly because they have a large surface area compared to their weight, and they can't shiver effectively. An infant with hypothermia might not look "cold"—they might just be unusually quiet, limp, and have bright red, cold skin.
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For the elderly, medications like beta-blockers can interfere with the body's ability to regulate temperature. A house that feels "a bit chilly" to a 30-year-old can be a death trap for an 80-year-old over a few days. This is "accidental hypothermia," and it kills thousands of people every year, often indoors.
Actionable steps for immediate safety
If you suspect someone is slipping into a dangerous state, follow this sequence:
- Check for responsiveness. Ask a complex question, not just "Are you okay?" Ask them to solve 5 plus 7.
- Call 911 immediately if they are confused, stop shivering, or are losing consciousness.
- Get them out of the elements. Even a garage or a tent is better than the open wind.
- Remove wet clothing. Cut it off if you have to, to avoid jostling their body too much.
- Insulate. Use blankets, sleeping bags, or even your own body heat if you have no other tools.
- Monitor breathing. If it stops or becomes dangerously slow, you may need to start CPR, but continue until the paramedics arrive. People have been successfully revived after being "frozen" for a long time—the medical saying is "you aren't dead until you're warm and dead."
The biggest takeaway is to trust your gut. Hypothermia isn't always a dramatic rescue on a mountain; it can happen in a damp basement or a broken-down car. If the person is acting "weird" and the air is cold, make the call. It's better to have a paramedic tell you they're just tired than to wait until they stop breathing.
Once you've called 911, stay on the line with the dispatcher. They can talk you through the "burrito wrap" technique or help you monitor their pulse. Keep the victim horizontal. Keeping them lying down helps maintain blood flow to the brain and prevents the heart from having to work harder against gravity while it's already struggling.