A body temperature below 97.8°F (36.6°C) is generally considered low, though “normal” varies more than most people realize. The long-standing benchmark of 98.6°F is outdated. A large systematic review combining data from 36 studies found the true average human body temperature is closer to 97.9°F (36.6°C), with healthy readings spanning roughly 96.4°F to 99.1°F depending on where and when you measure. So a single low reading doesn’t automatically signal a problem, but a consistently low temperature or one that drops below 95°F (35°C) is a different story.
What Counts as “Normal” Temperature
The 98.6°F figure dates back to a German study from the 1860s. Modern research places the average about half a degree lower, at 97.9°F when measured orally. But averages only tell part of the story. Healthy oral temperatures range from about 95.9°F to 99.5°F across individuals, and your own temperature shifts throughout the day by as much as 1.9°F.
Your body runs coolest in the early morning, typically between 4 and 6 a.m., about two hours before you wake up. It peaks in the early evening, around 8 p.m. This means a reading of 97.2°F at 6 a.m. is perfectly normal, while the same reading at 5 p.m. might be unusually low for you. Age matters too: older adults tend to run cooler overall, and their daily temperature low point shifts later in the morning compared to younger people.
Where You Measure Changes the Number
The spot on your body where you take a reading makes a real difference. Rectal measurements run highest, averaging about 98.2°F, while armpit (axillary) readings average around 96.3°F. Oral falls in the middle at roughly 97.5°F. That means an armpit reading of 96.5°F is completely unremarkable, even though it looks alarmingly low compared to the old 98.6 benchmark.
Accuracy varies by method too. Electronic rectal thermometers track closest to true core temperature. Ear (tympanic), oral, and armpit thermometers can be off by nearly a full degree Fahrenheit in either direction. If you’re getting a reading that concerns you, try measuring again with a different method or at a different time of day before assuming something is wrong.
Why Some People Run Cold
Several medical conditions can pull your baseline temperature lower than expected. An underactive thyroid is one of the most common culprits. Your thyroid gland sets the pace for your metabolism, and when it slows down, your body produces less heat. People with hypothyroidism often feel cold even in warm rooms, and their resting temperature may sit a degree or more below average.
Other conditions that can lower body temperature include adrenal insufficiency (where the adrenal glands don’t produce enough hormones to maintain normal metabolism), severe infections, low blood sugar, and conditions affecting the brain’s temperature-regulating center. Sepsis is a notable example: while many infections cause fever, sepsis sometimes drops temperature below 96.8°F, which can actually be a more dangerous sign than a high fever.
Certain medications interfere with your body’s ability to regulate heat. Beta-blockers, commonly prescribed for high blood pressure, reduce blood flow to the skin and decrease sweating. Antipsychotic medications can impair the brain’s thermostat directly. Sedatives like benzodiazepines and opioids can reduce your awareness of cold and suppress the shivering response that normally warms you back up. If you take any of these and notice consistently low readings, it’s worth mentioning to your prescriber.
Who Is Most Vulnerable
Infants and older adults have the hardest time keeping their core temperature stable, though for different reasons. Infants have a large surface area relative to their body mass, which means they lose heat quickly. Their sweat glands produce less output per gland, and a large portion of their blood volume can shift to the skin, which helps shed heat but leaves less circulating through the core. Because they can’t add layers or move to a warmer spot on their own, they depend entirely on caregivers to manage their environment.
Older adults face a different set of challenges. Metabolism naturally slows with age, producing less internal heat. The body’s shivering response weakens, circulation to the extremities decreases, and the ability to sense cold diminishes. Many older adults also take medications that compound the problem. An elderly person can develop a dangerously low temperature inside their own home if the heating is inadequate, without ever feeling particularly cold.
When Low Temperature Becomes Hypothermia
Hypothermia begins when core temperature drops below 95°F (35°C). It’s classified in three stages:
- Mild (90–95°F / 32–35°C): Shivering is intense and uncontrollable. You may have difficulty with fine motor tasks like buttoning a coat or using a phone. Thinking becomes slightly foggy.
- Moderate (82–90°F / 28–32°C): Shivering slows or stops entirely, which is a dangerous sign, not improvement. Confusion deepens, speech slurs, and coordination deteriorates significantly. The person may make irrational decisions, like removing clothing.
- Severe (below 82°F / 28°C): The person may lose consciousness. Heart rhythm becomes unstable. Breathing slows dramatically. Without emergency treatment, this stage is life-threatening.
One of the most dangerous features of hypothermia is that it erodes your ability to recognize it’s happening. The confused thinking it causes prevents self-awareness, which means people often don’t seek help until the condition is advanced. If someone around you is shivering uncontrollably, speaking unclearly, or acting confused after cold exposure, don’t wait for them to ask for help.
What to Do if Someone Is Too Cold
For mild cases, moving to a warm environment, replacing wet clothing with dry layers, and drinking warm, sweet, nonalcoholic beverages is usually enough. Focus warming efforts on the center of the body: the neck, chest, and groin. Warm compresses or an electric blanket work well. If using a hot water bottle or chemical heat pack, wrap it in a towel first to avoid burns on cold skin.
A few things that seem helpful can actually make the situation worse. Don’t try to warm the arms and legs directly by rubbing or applying heat. This can push cold blood from the extremities back to the heart too quickly, stressing the cardiovascular system and potentially triggering dangerous heart rhythms. This phenomenon, sometimes called “afterdrop,” is one reason hypothermia rewarming needs to be gradual and centered on the torso. Alcohol is also counterproductive: it dilates blood vessels near the skin, creating a temporary sensation of warmth while actually accelerating heat loss from the core.
For anyone showing signs of moderate or severe hypothermia (confusion, slurred speech, shivering that has stopped, loss of consciousness), call emergency services. Handle the person gently, keep them as still as possible, and insulate them from the cold ground while waiting for help. Rough movement can trigger heart rhythm problems in a severely hypothermic person.