Feeling cold when everyone around you seems comfortable usually comes down to how much heat your body produces, how well it holds onto that heat, or how accurately your nervous system reads temperature signals. Sometimes it’s a quirk of biology. Other times it points to a treatable medical condition like low thyroid function or iron deficiency.
How Your Body Controls Temperature
Your brain acts as a thermostat. A region called the hypothalamus receives signals from temperature sensors in your skin and internal organs, then decides whether to warm you up or cool you down. When those sensors detect cold, the brain triggers responses like shivering, which generates heat through rapid muscle contractions, and narrowing of blood vessels near the skin, which keeps warm blood closer to your core organs.
When everything works well, this system keeps your internal temperature hovering around 98.6°F (37°C), though individual baselines vary. Problems arise when any link in this chain is disrupted: your metabolic engine runs too slowly, your blood doesn’t carry enough oxygen to fuel heat production, or your blood vessels overreact and restrict flow to your fingers and toes.
Low Thyroid Function
Hypothyroidism is one of the most common medical reasons people feel persistently cold. Your thyroid gland sets the pace for your metabolism. When it underperforms, every cell in your body burns less energy, producing less heat as a byproduct. The result is a lower resting metabolic rate and a body that struggles to stay warm, especially in cooler environments.
Doctors screen for this with a blood test measuring TSH (thyroid-stimulating hormone). Normal levels fall between roughly 0.4 and 4.5 mIU per liter. A TSH above 4.5 with low levels of active thyroid hormone confirms clinical hypothyroidism. Some people have elevated TSH but normal thyroid hormone levels, a condition called subclinical hypothyroidism, which can still cause subtle symptoms like cold sensitivity, fatigue, and dry skin. If you’re always cold and also dealing with unexplained weight gain, sluggishness, or thinning hair, thyroid function is worth checking.
Iron Deficiency and Anemia
Iron is essential for making hemoglobin, the protein in red blood cells that carries oxygen from your lungs to the rest of your body. When iron stores drop, your tissues receive less oxygen, and your body can’t generate heat as efficiently. Cold hands and feet are a classic early sign, sometimes appearing before a full-blown anemia diagnosis.
Iron deficiency is typically defined by a ferritin level (a measure of stored iron) below 30 nanograms per milliliter. Levels at or below 15 ng/mL indicate severe depletion. Beyond cold extremities, you might notice headaches, brittle nails, or unusual fatigue. Women with heavy periods, vegetarians, and frequent blood donors are at higher risk. A simple blood panel can identify the problem, and it’s one of the more straightforward causes to fix.
Vitamin B12 deficiency produces a similar effect through a different route. B12 is needed to build healthy red blood cells, so when levels are low, the body develops a type of anemia that reduces oxygen delivery just like iron deficiency does. People who eat little or no animal products, or those with digestive conditions that impair absorption, are especially vulnerable.
Women Feel Cold More Often, and Biology Explains Why
If you’ve ever fought over the office thermostat, you’ve seen this play out. Women tend to have lower resting metabolic rates than men at all temperatures, with the gap becoming statistically significant in cooler conditions (below about 64°F or 18°C). One analysis found that traditional indoor climate standards, based on male metabolic rates, may overestimate female heat production by as much as 35%.
The difference isn’t just metabolic. Women typically have lower blood flow rates to their extremities, which means less warm blood reaching their fingers and toes. Hormonal fluctuations throughout the menstrual cycle also influence core temperature and blood vessel behavior. Combined with generally smaller body frames and less muscle mass, these factors make women more likely to report feeling cold in the same room where men feel perfectly comfortable.
Muscle Mass and Body Composition
Your muscles are your body’s primary furnace. Resting metabolic rate, which accounts for 60 to 80 percent of the calories you burn each day, is strongly linked to how much muscle you carry. Research shows that each additional kilogram of muscle mass increases resting energy expenditure by about 24 calories per day. That may sound modest, but the cumulative effect across your whole body is significant for heat production.
Interestingly, body fat percentage has almost no independent effect on metabolic rate. Fat acts as insulation, slowing heat loss through the skin, but it doesn’t generate much heat on its own. So a person with very low body fat and limited muscle mass gets a double hit: they produce less internal heat and lose what they do produce more quickly. This is one reason people who are underweight or who have recently lost significant muscle (from illness, aging, or extreme dieting) often feel cold.
Raynaud’s Phenomenon
Some people don’t just feel cold in general. Their fingers or toes turn white or blue in response to cool air or stress, sometimes becoming numb or painful before flushing red as blood flow returns. This is Raynaud’s phenomenon, a condition where the small blood vessels in the extremities spasm and temporarily shut down circulation far more aggressively than normal.
Primary Raynaud’s is the more common form and isn’t linked to any underlying disease. It tends to appear in teens or young adults and is more frequent in women and people living in colder climates. Secondary Raynaud’s is associated with autoimmune conditions and tends to be more severe. Doctors can distinguish between the two by examining the tiny blood vessels at the base of your fingernails under magnification. Cold exposure and emotional stress are the most reliable triggers for attacks.
Diabetes and Nerve Damage
Long-standing high blood sugar damages the small nerves in your hands and feet, a condition called peripheral neuropathy. This can distort temperature perception in both directions. Some people lose the ability to sense cold accurately, while others experience persistent sensations of coldness even when their skin temperature is normal. The nerve signals simply misfire.
Diabetes also promotes inflammation of blood vessel walls and hardening of the arteries, particularly in the lower legs and feet. This restricts blood flow to the extremities, making them genuinely cooler and slower to warm up. If you have diabetes and notice that your feet always feel cold or that you can’t tell whether bathwater is too hot, nerve damage and reduced circulation are likely contributing.
Other Factors Worth Considering
Several less obvious variables can shift your temperature comfort zone. Dehydration reduces blood volume, making it harder for your body to distribute heat evenly. Chronic sleep deprivation disrupts hormonal and metabolic rhythms that influence thermoregulation. Aging naturally reduces metabolic rate and thins the fat layer under the skin, which is why older adults frequently keep their homes warmer.
Some medications also play a role. Beta-blockers, commonly prescribed for high blood pressure, slow heart rate and reduce blood flow to the extremities. Certain antidepressants and stimulant medications can alter temperature regulation as a side effect. If feeling cold started or worsened around the time you began a new medication, that timing is worth noting.
For many chronically cold people, the cause isn’t a single dramatic problem but a combination of smaller factors: being female, having a lighter frame, carrying less muscle, sitting at a desk all day, or eating too few calories. Each one nudges your thermostat slightly toward “cold,” and together they can make you the person who always brings a sweater.