Your body temperature can drop for reasons ranging from completely normal daily fluctuations to serious medical emergencies. The threshold that matters: a core temperature below 35°C (95°F) is classified as hypothermia. But plenty of factors can pull your temperature down without crossing that line, and understanding them helps you recognize when something is routine and when it signals a problem.
How Your Body Loses Heat
Your body sheds heat through four physical mechanisms, and all of them speed up when conditions work against you. Radiation is the biggest one, accounting for roughly 60% of heat loss. Your blood carries warmth from deep tissues to the skin’s surface, where it radiates outward as infrared energy, the same way a warm sidewalk releases heat after sunset. This works whenever your skin is warmer than your surroundings.
Evaporation handles about 22% of heat loss. Every time moisture leaves your skin, whether from sweat or just normal water vapor, it pulls energy with it. This happens even when you’re not visibly sweating. When the air around you is hotter than your skin, evaporation becomes your only cooling option, since radiation and convection can’t push heat toward something that’s already warmer.
Conduction and convection together account for the remaining 15% or so. Conduction is direct heat transfer from your skin to whatever it touches. Water conducts heat 100 times faster than air, which is why falling into cold water is so much more dangerous than standing in cold air at the same temperature. Convection is heat carried away by moving air or water flowing past your skin. Wind chill is convection in action.
Cold Environments and Exposure
The most obvious cause of a temperature drop is losing heat faster than your body can produce it. Cold air, wind, wet clothing, and immersion in water all accelerate the process. Your body fights back by constricting blood vessels near the skin to keep warm blood closer to your organs, and by triggering shivering to generate heat through rapid muscle contractions. But if exposure is prolonged or the cold is extreme, these defenses get overwhelmed.
Mild hypothermia (32 to 35°C, or 90 to 95°F) causes intense shivering, confusion, and clumsiness. Moderate hypothermia (28 to 32°C, or 82 to 90°F) slows shivering and deepens confusion. Severe hypothermia, below 28°C (82°F), can cause shivering to stop entirely as the body runs out of energy, and heart rhythm becomes dangerously irregular.
Your Body’s Natural Temperature Cycle
Not every temperature dip is cause for concern. Your core temperature follows a 24-hour rhythm, rising during the day and falling at night. The lowest point hits in the early morning hours, typically between 3 and 5 a.m., and the swing from peak to trough is usually greater than 1°C (about 1.8°F). If you’ve ever noticed feeling colder in the middle of the night, that’s your circadian clock at work, not a sign of illness.
Thyroid Problems and Metabolism
Your thyroid gland acts like a dial for your metabolic furnace. Thyroid hormones stimulate the energy-burning pathways that produce heat as a byproduct, including processes that keep your muscles, organs, and even fat tissue generating warmth. When your thyroid is underactive (hypothyroidism), that furnace turns down. You produce less internal heat, and cold intolerance becomes one of the hallmark symptoms.
Thyroid hormones also interact with your sympathetic nervous system, the “fight or flight” network that controls blood vessel tone and shivering. With less thyroid hormone in circulation, these heat-preserving responses become sluggish. People with untreated hypothyroidism often feel cold when everyone around them is comfortable, and in severe cases, a condition called myxedema coma can cause dangerously low body temperature.
Low Blood Sugar
Your body needs fuel to maintain its temperature, and glucose is a primary energy source. When blood sugar drops significantly, your thermoregulation shifts in a measurable way. Research has shown that hypoglycemia doesn’t change how your body handles heat, but it dramatically raises the bar for triggering shivering during cold exposure. In one study, the core temperature threshold at which shivering kicked in dropped by more than half a degree Celsius during low blood sugar compared to normal levels. In practical terms, your body waits much longer to start defending itself against the cold, letting your temperature slide further before mounting a response.
Alcohol
Alcohol creates a deceptive warmth. It dilates blood vessels near the skin’s surface, flooding your skin with warm blood. You feel warmer, and your skin flushes, but that blood is now radiating heat outward much faster than usual. Research suggests this isn’t just a side effect of the blood vessel changes. Alcohol appears to actively lower the temperature your brain is trying to maintain, essentially turning down your internal thermostat. Your body then coordinates multiple cooling responses, including increased sweating, as though the lower temperature is the new target. This is why drinking in cold weather is genuinely dangerous: you feel fine while your core temperature quietly drops.
Medications That Lower Temperature
Several classes of drugs interfere with your body’s ability to regulate heat. Antipsychotic medications are the most well-documented culprits. The earliest antipsychotic drug, chlorpromazine, was actually used in surgery to suppress the body’s warming responses before anyone understood its psychiatric effects. These medications can block receptors in the brain that help regulate temperature, and some also block signals in the peripheral nervous system that trigger vasoconstriction and shivering, the two main defenses against cooling. Newer atypical antipsychotics carry the same risk, particularly those with strong effects on serotonin receptors involved in thermoregulation. Sedatives, opioids, and general anesthetics can also blunt the body’s heat-preserving reflexes.
Serious Infections
Most people associate infection with fever, but serious systemic infections (sepsis) can cause the opposite. In one large study, hypothermic sepsis patients had a 28-day mortality rate of 45.7%, compared to 27.1% for those who developed high fevers. The temperature drop appears to be an energy-conservation strategy. Animal research suggests that when the body’s metabolic reserves are limited, it shifts toward tolerating the infection rather than mounting an aggressive, energy-expensive fever response.
Several factors predict who develops hypothermia rather than fever during sepsis: older age, lower body weight, abdominal infections, and colder environmental temperatures. People with fewer metabolic reserves seem more likely to mount this hypothermic response. Whether this is the body making a smart trade-off or simply failing to respond properly is still debated, but the clinical reality is clear: a dropping temperature during infection is a red flag, not a sign that things are improving.
Brain and Spinal Cord Injuries
Your hypothalamus, a small region deep in the brain, acts as your body’s thermostat. It senses blood temperature, receives signals from temperature receptors in the skin, and coordinates the responses that keep you at roughly 37°C. Damage to this area from traumatic brain injury, stroke, or tumors can disrupt the entire system.
Spinal cord injuries are particularly devastating for temperature control. The hypothalamus may still function, but the communication lines between it and the rest of the body are severed. Injuries above the T6 vertebra disconnect the brain from most of the sympathetic nervous system, meaning the body can no longer constrict or dilate blood vessels on command, trigger sweating effectively, or coordinate shivering below the injury site. On top of that, reduced muscle mass below the injury means less heat production, and the loss of skin sensation means these individuals can’t feel when they’re getting dangerously cold or hot. People with high spinal cord injuries often find their body temperature drifting toward whatever the room temperature is.
Why Newborns and Elderly People Are Vulnerable
Newborns face a steep thermal challenge from the moment of birth. They leave an environment that’s body temperature and enter one that’s significantly cooler, while simultaneously losing heat through evaporation from wet skin. Their primary defense is a special type of fat called brown adipose tissue, which burns calories directly to produce heat rather than relying on shivering. Adult muscles are far more efficient at shivering, but newborn musculature is immature and their blood supply to muscles is still developing. In the womb, fetuses actually produce about twice the heat per kilogram that adults do, but this advantage disappears quickly after birth as energy reserves deplete. Premature infants are at the highest risk because they have less brown fat and a larger surface-area-to-weight ratio, meaning heat escapes faster.
Older adults face a different set of problems. Metabolic rate naturally declines with age, producing less baseline heat. The shivering response weakens over time, blood vessel reflexes slow down, and the ability to sense temperature changes diminishes. Many older adults also take medications that further impair thermoregulation, eat less (reducing the heat generated by digestion), and have less body fat for insulation. Indoor hypothermia in elderly people living in poorly heated homes is a well-recognized and underappreciated risk, particularly during winter months.