A low body temperature is anything below the normal range of about 97°F to 99°F (36.1°C to 37.2°C). When core body temperature drops below 95°F (35°C), it crosses into hypothermia, a potentially dangerous condition that requires immediate attention. But even temperatures between 95°F and 97°F can signal that something is off, whether from cold exposure, an underlying health condition, or simply your individual baseline running cooler than average.
What Counts as “Normal” Has Changed
For over a century, 98.6°F (37°C) was treated as the gold standard for normal human body temperature. That number came from a German study in the 1860s. More recent research tells a different story. A large analysis published in eLife found that average body temperature in the United States has been steadily declining since the Industrial Revolution, dropping by about 0.03°C per decade of birth. Men born in the early 1800s ran roughly 0.59°C (about 1°F) warmer than men today, and women have shown a similar decline since the 1890s.
The upshot: today’s average oral temperature is closer to 97.5°F to 97.9°F for most adults. So if your thermometer reads 97.something, that’s likely perfectly normal. A reading below 97°F, especially if it’s unusual for you, is worth paying attention to.
When Low Temperature Becomes Hypothermia
Hypothermia begins at 95°F (35°C) and is classified in three stages based on how far the body’s core temperature has fallen:
- Mild (90°F to 95°F / 32.2°C to 35°C): Shivering, confusion, poor coordination, and slurred speech. The body is still actively trying to generate heat through shivering.
- Moderate (82.4°F to 90°F / 28°C to 32.2°C): Shivering stops, which is actually a bad sign. Confusion worsens, drowsiness sets in, and heart rate slows.
- Severe (below 82.4°F / 28°C): Loss of consciousness, dangerously slow breathing and heart rate, and risk of cardiac arrest.
The shift from mild to moderate hypothermia can happen faster than people expect, particularly in wet or windy conditions. Someone who seems “just cold” can deteriorate quickly.
Medical Causes of Low Body Temperature
Cold weather is the obvious cause, but a persistently low body temperature that shows up on routine checks, even indoors, can point to other issues. An underactive thyroid is one of the most common culprits. The thyroid gland controls your metabolic rate, and when it slows down, so does heat production. People with untreated hypothyroidism often feel cold all the time and may register temperatures below 97°F.
Other conditions that can lower body temperature include severe infections (sepsis can paradoxically cause low rather than high temperature, especially in older adults), uncontrolled diabetes, malnutrition, and adrenal insufficiency. Certain medications, including some sedatives and antipsychotics, can impair the body’s ability to regulate temperature. Older adults and very young children are more vulnerable because their thermoregulation systems are less efficient.
Alcohol also plays a role. It dilates blood vessels near the skin, which makes you feel warmer while actually accelerating heat loss from your core. This is why hypothermia is a real risk for anyone who’s been drinking in cold conditions.
What to Do if Someone Is Too Cold
If someone’s temperature has dropped below 95°F or they’re showing signs of hypothermia (uncontrollable shivering, confusion, fumbling hands, slurred speech), call emergency services. While waiting for help, the priority is gentle, gradual warming focused on the body’s core.
Move the person out of the cold or, if that’s not possible, shield them from wind, especially around the head and neck. Lay a blanket underneath them to insulate from cold ground. Remove any wet clothing and replace it with dry layers. Apply warm compresses (or a towel-wrapped hot water bottle) to the neck, chest, and groin. Offer warm, sweet, non-alcoholic drinks if the person is alert enough to swallow safely.
What not to do matters just as much. Don’t try to warm someone rapidly with a hot bath or heating lamp. Don’t rub or heat the arms and legs directly, as this can push cold blood from the extremities back to the heart too quickly and cause dangerous heart rhythms. Don’t offer alcohol, which slows rewarming, or cigarettes, which constrict the blood vessels needed for circulation.
The Coldest Temperatures on Earth
For context on just how cold things can get: the lowest temperature ever detected on Earth’s surface was minus 136°F (minus 93.2°C), recorded by satellite on August 10, 2010, on a high ridge of the East Antarctic Plateau between Dome Argus and Dome Fuji. These readings come from clear winter nights in small hollows along the ridge where cold air pools and settles.
In physics, the absolute lowest temperature possible is minus 459.67°F (minus 273.15°C), known as absolute zero or 0 on the Kelvin scale. At this point, atoms would have essentially no thermal energy left. No place in the known universe has reached absolute zero naturally, though laboratory experiments have come within fractions of a degree.