Feeling cold when others around you seem comfortable usually comes down to how well your body produces heat, retains it, or delivers warm blood to your extremities. Normal body temperature hovers around 98.6°F (37°C), though healthy individuals can range from 97°F to 99°F depending on the time of day and activity level. When any step in the chain of heat production and distribution breaks down, you feel cold, whether or not the room is actually chilly.
How Your Body Produces and Keeps Heat
Your body generates heat as a byproduct of metabolism, the constant chemical process of converting food into energy. The faster your metabolism runs, the more heat you produce. Muscles are especially good heat generators, which is why you shiver when you’re cold: your body forces rapid muscle contractions to create warmth in a hurry.
Once heat is produced, your body works to hold onto it. Subcutaneous fat, the layer of fat just beneath your skin, acts as insulation. Research in the American Journal of Clinical Nutrition found that thermal insulation is directly proportional to subcutaneous fat thickness. In overweight and obese women studied at room temperature (about 68°F), total heat losses were lower and internal temperature dropped more slowly than in normal-weight women. This is why people with very low body fat or a low BMI often report feeling cold more easily. They simply have less built-in insulation.
Blood flow is the other critical piece. Your cardiovascular system acts like a central heating network, carrying warm blood from your core to your fingers, toes, nose, and ears. When your body senses cold, it constricts blood vessels in your extremities to keep your vital organs warm. That’s normal. But several medical conditions can make this response too aggressive or reduce blood flow permanently.
Thyroid Problems and Metabolism
An underactive thyroid (hypothyroidism) is one of the most common medical reasons people feel persistently cold. Thyroid hormones regulate energy expenditure and thermogenesis, your body’s heat-generating processes. When thyroid hormone levels are low, your basal metabolic rate drops, and you produce less heat overall. Cold intolerance is a hallmark symptom.
The effects go beyond just lower heat production. Thyroid hormones also help relax blood vessel walls. When levels are low, small arteries in your extremities resist relaxation, which reduces blood flow to your hands and feet. So hypothyroidism hits you twice: less heat generated at the core and less warm blood reaching your fingers and toes. Other common signs include unexplained weight gain, fatigue, and dry skin. A simple blood test can check your thyroid function.
Iron and Vitamin Deficiencies
Iron-deficiency anemia is another frequent culprit. Iron is essential for making hemoglobin, the protein in red blood cells that carries oxygen from your lungs to every tissue in your body. When iron is low, your tissues get less oxygen, which directly impairs two key cold-weather defenses: your body’s ability to constrict peripheral blood vessels (which conserves heat) and its ability to ramp up metabolic rate (which generates heat). Animal studies illustrate the effect dramatically. Iron-deficient rats placed in a cold environment rapidly became hypothermic, and restoring their red blood cell levels brought their temperature regulation back to normal.
Vitamin B12 deficiency works through a similar path. B12 is necessary for red blood cell production, so a shortage leads to fewer healthy red blood cells and, eventually, anemia. The downstream result is the same: reduced oxygen delivery, less heat production, and cold hands and feet. Vegetarians, vegans, and older adults are at higher risk for B12 deficiency because the vitamin is found primarily in animal products and becomes harder to absorb with age.
Poor Circulation and Vascular Conditions
Peripheral artery disease (PAD) narrows the arteries that supply blood to your legs and arms. The narrowing happens when fatty deposits (plaque) build up on artery walls, reducing blood flow. One of the telltale signs is coldness in one lower leg or foot compared to the other side. PAD is more common in people who smoke, have high blood pressure, high cholesterol, or diabetes. Because the reduced blood flow develops gradually, many people attribute the coldness to age or weather before realizing something else is going on.
Raynaud’s phenomenon is a more dramatic version of the body’s normal cold response. In people with Raynaud’s, the small arteries supplying the fingers and toes go into exaggerated spasm when exposed to cold or emotional stress. The digits turn white (as blood flow cuts off), then blue (as oxygen depletes), then red (as blood rushes back in). Attacks can be triggered by something as minor as walking into an air-conditioned building on a warm day. Prolonged typing, smoking, and certain medications like beta-blockers can also set off episodes.
Low Blood Sugar and Dehydration
When your blood sugar drops too low (hypoglycemia), your body releases adrenaline and noradrenaline to push sugar levels back up. These stress hormones trigger a recognizable set of symptoms: sweating, trembling, a racing heartbeat, and anxiety. The sweating, in particular, can make you feel suddenly cold and clammy, even indoors. This is common in people with diabetes who take insulin, but it can also happen in anyone who skips meals or exercises intensely without eating.
Dehydration affects temperature regulation by reducing blood volume. With less blood circulating, your body has a harder time managing its normal heating and cooling responses. The reduced blood volume weakens the cardiovascular system’s ability to deliver warmth to the skin and extremities. Most people associate dehydration with overheating, but it disrupts thermoregulation in both directions.
Nerve Damage and Temperature Perception
Sometimes the problem isn’t that your body is actually colder. It’s that your nerves are misreporting temperature. Diabetic neuropathy, nerve damage caused by chronically high blood sugar, is a prime example. In people with diabetic neuropathy, the nerves that sense temperature become less accurate. Studies measuring cold perception thresholds found that people with neuropathy couldn’t detect cold until the temperature dropped significantly lower than what people with healthy nerves could feel. Their cold detection threshold in the lower legs was around 20°C, compared to about 24°C in people without neuropathy.
This creates a paradox: some people with nerve damage feel cold sensations that aren’t there (neuropathic cold), while others fail to notice genuinely cold temperatures. Both situations stem from damaged sensory fibers that no longer transmit temperature signals accurately. The smaller nerve fibers responsible for warmth detection tend to be damaged first, followed by the slightly larger fibers that detect cold.
Sleep Deprivation
Missing sleep disrupts the coordinated way your body manages blood flow to your skin. Research tracking skin temperatures after sleep deprivation found that going without sleep causes your hands to become colder while your feet actually warm up. Normally, your body coordinates blood vessel dilation and constriction across your extremities in a synchronized pattern. Sleep deprivation breaks that coordination, disrupting the sympathetic nervous system’s control of skin blood flow. In prolonged sleep deprivation studies in animals, core body temperature progressively declines despite increased food intake and energy expenditure, suggesting the body loses its ability to maintain thermal balance the longer it goes without rest.
Body Size, Muscle Mass, and Sex Differences
People with less muscle mass produce less metabolic heat at rest because muscle tissue is metabolically active and generates warmth as a byproduct. This partly explains why women, who on average carry less muscle and more body fat than men, often report feeling colder. The insulation from body fat helps retain heat, but it doesn’t compensate fully if heat production is lower to begin with.
Interestingly, higher body fat does change where you feel warm and cold. Research using infrared temperature measurements found that fingernail-bed temperature was positively related to body fat percentage, meaning people with more fat had warmer fingertips. But abdominal skin temperature showed the opposite pattern: it was negatively associated with body fat. The fat layer over the abdomen insulates so well that less heat escapes through the skin there, making the surface feel cooler to the touch even though the core stays warm.
Small body size also plays a role independent of fat and muscle. A smaller body has a higher surface-area-to-volume ratio, meaning more skin surface (where heat escapes) relative to the body’s heat-producing mass. This is why children and petite adults tend to lose heat faster in cold environments.