A consistently low body temperature usually reflects something your body is doing, not something broken. Normal body temperature isn’t a fixed 98.6°F (37°C) for everyone. It ranges from about 97°F to 99°F (36.1°C to 37°C), varying by person, time of day, and how you measure it. If your readings regularly fall at or below the low end of that range, several common factors could explain why.
Your Thermometer Might Be the Problem
Before investigating medical causes, consider your measurement method. Forehead thermometers are convenient but tend to be less accurate, especially in cold rooms, direct sunlight, or if your skin is sweaty. Ear thermometers can give misleading readings when earwax buildup or the shape of the ear canal interferes. Oral thermometers offer much better accuracy, though drinking something cold or breathing through your mouth beforehand can drag the number down temporarily. If you’re getting readings that seem unusually low, try an oral thermometer under your tongue with your mouth closed for the full recommended time.
When You Measure Matters
Your body temperature isn’t constant throughout the day. It follows a predictable cycle tied to your internal clock. Temperature starts climbing during the last hours of sleep and peaks sometime in the late afternoon or early evening. It drops again at night as your body prepares for sleep, and most people also experience a small dip between 2 p.m. and 4 p.m. If you’re checking your temperature first thing in the morning or during that afternoon trough, a reading in the mid-to-low 97s is completely normal and doesn’t signal a problem.
Underactive Thyroid
The thyroid gland is probably the single biggest factor in how much heat your body produces at rest. Thyroid hormones regulate thermogenesis, the process of generating heat, by acting on multiple organs simultaneously. They increase metabolic activity in skeletal muscle by driving ion pumps that consume energy and release heat as a byproduct. They also activate a protein in fat tissue that essentially short-circuits energy production, converting calories directly into warmth instead of storing them. On top of these direct effects, thyroid hormones influence your sympathetic nervous system, the “fight or flight” wiring that controls how vigorously your body burns fuel.
When thyroid hormone levels drop, as in hypothyroidism, all of these heat-generating pathways slow down. The result is a lower baseline temperature along with the classic symptoms: fatigue, weight gain, dry skin, and feeling cold when others are comfortable. Hypothyroidism is common, affecting roughly 5% of Americans, and a simple blood test can confirm it. If your low temperature comes with persistent tiredness or unexplained weight changes, thyroid function is worth checking.
Low Iron Levels
Iron deficiency impairs your body’s ability to regulate temperature through at least two separate mechanisms. First, it disrupts thyroid hormone processing, slowing the same heat-generating pathways described above. Second, and perhaps more importantly, it interferes with your body’s control over blood flow to the skin. Normally, when you’re cold, your nervous system constricts blood vessels near the surface to keep warm blood closer to your core. Iron-deficient individuals lose some of this vascular control, allowing heat to escape more easily.
Iron deficiency also reduces oxidative metabolism in muscles, which weakens your ability to shiver effectively. Shivering is your body’s emergency heating system, and when it can’t work properly, you lose a key defense against temperature drops. This is why people with iron deficiency anemia often report feeling cold all the time, not just having low thermometer readings.
Blood Sugar Drops
Low blood sugar consistently lowers body temperature. In controlled studies, hypoglycemia reduced core temperature by about 0.3°C to 0.4°C (roughly half a degree Fahrenheit), while normal blood sugar levels produced no temperature change at all. This effect held true regardless of insulin levels, meaning the temperature drop is tied to the lack of fuel itself, not to whatever caused the blood sugar to fall.
You don’t need to be diabetic to experience this. Skipping meals, very low-calorie diets, prolonged fasting, or intense exercise without adequate food can all push blood sugar low enough to affect heat production. If your low readings tend to coincide with long gaps between meals or periods of under-eating, this connection is worth paying attention to.
Not Eating Enough Overall
Calorie restriction beyond short-term blood sugar dips can lower your resting temperature over time. When your body consistently receives fewer calories than it needs, it downshifts its metabolic rate to conserve energy. Less metabolic activity means less heat. This is one reason people on very restrictive diets or those with eating disorders frequently report feeling cold. The body treats reduced food intake as a signal to slow everything down, and temperature is one of the first things to drop.
Age-Related Changes
Aging affects temperature regulation in subtle but meaningful ways. While the “normal” set point doesn’t change dramatically, older adults lose some of the mechanisms that maintain it. Subcutaneous fat, the layer of fat just beneath the skin that acts as insulation, decreases with age. The ability to shiver diminishes. And the body’s sweating and vasomotor responses become less responsive, making it harder to detect and respond to temperature changes in either direction.
This means an older adult with a temperature of 96.5°F might not feel particularly cold, even though their body is losing heat faster than it’s producing it. For people over 65, a persistently low reading deserves more attention than the same number in a healthy 30-year-old.
When Low Temperature Becomes Hypothermia
There’s a clear medical line between “running cool” and a dangerous condition. Hypothermia begins at 95°F (35°C). Below that threshold, the body starts losing its ability to rewarm itself:
- Mild hypothermia (95°F to 89.6°F): shivering, confusion, difficulty with coordination
- Moderate hypothermia (89.6°F to 82.4°F): shivering stops, drowsiness deepens, heart rhythm may become irregular
- Severe hypothermia (below 82.4°F): loss of consciousness, dangerously slow heart rate, life-threatening
If your temperature is consistently in the 96°F to 97°F range and you feel fine otherwise, you’re almost certainly not hypothermic. You’re just someone whose baseline runs a bit low. But if your readings dip below 95°F, or you experience confusion, slurred speech, or extreme drowsiness alongside a low reading, that’s a medical emergency.
Practical Steps if You Run Cold
If your temperature is consistently low but above 95°F, start by ruling out the most common and fixable causes. Make sure you’re eating enough calories and not going long stretches without food. Check whether your iron levels are adequate, particularly if you menstruate, donate blood regularly, or eat a plant-based diet. Ask about thyroid testing if low temperature comes alongside fatigue, constipation, or weight gain that doesn’t match your eating habits.
Track your temperature at the same time each day, ideally in the late afternoon when it naturally peaks, using an oral thermometer. A few days of consistent readings gives you a much clearer picture than a single measurement taken at random. If your afternoon readings still come in below 97°F and you’re experiencing other symptoms, that pattern gives your doctor something concrete to investigate.