Hypothermia is a medical emergency that occurs when your core body temperature drops below 95°F (35°C). Normal body temperature hovers around 98.6°F, so it doesn’t take a dramatic plunge to reach dangerous territory. The condition progresses through stages, each with distinct warning signs, and understanding those stages can make the difference between a close call and a life-threatening situation.
How Hypothermia Is Classified
Doctors break hypothermia into three stages based on core body temperature:
- Mild: 90°F to 95°F (32.2°C to 35°C)
- Moderate: 82.4°F to 90°F (28°C to 32.2°C)
- Severe: Below 82.4°F (28°C)
These thresholds matter because the body’s protective mechanisms change at each level. In mild hypothermia, your body is still fighting back. By the severe stage, many of those defenses have shut down entirely.
What It Feels Like as It Progresses
Shivering is the first and most recognizable sign. It’s your body’s automatic attempt to generate heat through rapid muscle contractions. In the mild stage, you’ll also notice clumsiness, slurred speech, and difficulty thinking clearly. Your hands may fumble with zippers or buttons that would normally be easy to manage.
As hypothermia moves into the moderate range, something counterintuitive happens: shivering stops. This is not a sign of improvement. It means your body has exhausted its ability to warm itself. Confusion deepens, drowsiness sets in, and breathing becomes slow and shallow. People in this stage often make poor decisions, like removing clothing, because the brain is no longer processing temperature signals correctly.
In severe hypothermia, the pulse weakens significantly, breathing may be barely detectable, and loss of consciousness follows. The heart becomes electrically unstable at these temperatures, meaning even rough physical handling can trigger a fatal heart rhythm. This is why rescue teams are trained to move hypothermia victims as gently as possible.
Infants show hypothermia differently. Rather than shivering (which very young babies can’t do effectively), a hypothermic infant will have bright red, cold skin and unusually low energy.
Why Some People Are More Vulnerable
Babies and older adults face the highest risk, and for overlapping but distinct reasons.
Babies have a large body surface area relative to their weight, which means they lose heat faster than adults. Their temperature regulation systems are still developing, they have very little insulating body fat, and they can’t shiver effectively to generate warmth. A baby left in a cold room can become hypothermic in conditions an adult would tolerate without trouble. If a child starts shivering outdoors, that’s the signal to bring them inside immediately.
Older adults face a different set of challenges. Baseline body temperature naturally decreases with age, so an older person starts closer to the hypothermia threshold. Their bodies produce less heat, have less insulating fat, and are slower to constrict blood vessels near the skin (a key mechanism for conserving warmth). They also shiver less effectively. These changes can make indoor hypothermia a real concern for elderly people living in poorly heated homes, especially during winter months.
Beyond age, other factors increase risk: alcohol use (which dilates blood vessels and accelerates heat loss while impairing judgment), prolonged water immersion (water pulls heat from the body roughly 25 times faster than air), homelessness, and certain medications that interfere with temperature regulation.
How Hypothermia Is Detected
Diagnosing hypothermia sounds simple: take a temperature reading. In practice, it’s trickier than you’d expect. Standard thermometers often can’t read below about 93°F, which means they may show a low number without revealing just how low a person’s temperature actually is. When hypothermia is suspected, medical teams use special rectal thermometers capable of reading well below 95°F to get an accurate core temperature. An oral or forehead reading won’t suffice because those methods don’t reliably reflect what’s happening deep in the body.
What to Do Before Help Arrives
If you suspect someone has hypothermia, the priority is stopping further heat loss. Move them to a warm, sheltered area if possible. Remove any wet clothing and cover them with blankets, coats, or anything dry and insulating. Focus warmth on the core of the body (chest, neck, head, groin) rather than the extremities.
Handle the person gently. A cold heart is electrically irritable, and sudden jolts or rough movement have been reported to trigger dangerous heart rhythms. Don’t rub their arms and legs vigorously or put them in a hot bath. These actions can push cold blood from the limbs back toward the heart too quickly, which creates its own set of problems (more on that below). Warm, sweet drinks can help someone who is alert and able to swallow, but avoid alcohol and caffeine.
How Hospitals Treat Hypothermia
Treatment depends on severity. For mild cases, passive rewarming (warm blankets, a heated room, warm fluids) is often enough. The body can still generate heat on its own at this stage, so the goal is simply to stop the loss and let it recover.
Moderate and severe cases require active rewarming. This can include warmed IV fluids, heated humidified oxygen, and in the most critical situations, a technique where the blood is drawn out of the body, warmed externally, and returned. This approach is the preferred method for patients in cardiac arrest from hypothermia. For patients who meet certain criteria (cardiac arrest, core temperature below 86°F, dangerously low blood pressure, or unstable heart rhythms), transfer to a specialized center for this treatment is recommended. About 40% of patients who receive it after hypothermic cardiac arrest survive with good neurological outcomes, a remarkable figure given how dire the situation is.
The Afterdrop Problem
One of the trickiest aspects of treating hypothermia is a phenomenon called afterdrop. When rewarming begins, blood vessels in the arms and legs start to relax and open up again. This sends a wave of cold blood from the extremities back into the core, temporarily dropping the core temperature even further, sometimes right after treatment has started. Afterdrop can worsen heart rhythm problems and, in some cases, trigger cardiac arrest. It’s the main reason why rewarming needs to be controlled and monitored rather than done rapidly or haphazardly.
Indoor Hypothermia Is More Common Than You’d Think
Hypothermia doesn’t require a blizzard or a frozen lake. It can develop indoors in homes kept below 60°F, particularly in elderly people who may not perceive the cold as acutely. Wet clothing, air conditioning, and even swimming in water that feels comfortable (but is below body temperature) can gradually lower core temperature over hours. The key factor isn’t how extreme the cold is. It’s how long the exposure lasts relative to how quickly your body can compensate.