Feeling cold all the time usually signals that your body is either producing less heat than it should, losing heat faster than normal, or struggling to circulate warm blood to your extremities. The most common culprits are an underactive thyroid, iron deficiency, low body weight, or poor circulation. In many cases, the cause is identifiable and treatable.
Your Thyroid Sets Your Internal Thermostat
The single most common medical explanation for constant cold sensitivity is hypothyroidism, a condition where your thyroid gland doesn’t produce enough hormones. Thyroid hormones directly control your basal metabolic rate, which is essentially how much energy your body burns at rest. When levels drop, your resting energy expenditure falls, your body generates less heat, and you feel cold in environments that don’t bother other people.
Thyroid hormones also activate a specific type of fat tissue called brown fat, which exists primarily to burn calories and generate warmth. In people with low thyroid function, this heat-generating process slows down significantly. The result is a body that’s running cooler across the board, not just in your hands and feet but at your core.
Other signs of hypothyroidism include fatigue, unexplained weight gain, dry skin, thinning hair, and constipation. A simple blood test measuring TSH (thyroid-stimulating hormone) can confirm or rule it out. Normal TSH falls between 0.5 and 5.0 microunits per milliliter, though the upper limit may be set higher for older adults. If your TSH is elevated, it means your brain is working harder to stimulate a sluggish thyroid. Treatment with thyroid hormone replacement typically resolves cold sensitivity within weeks to months.
Iron Deficiency and Anemia
Iron deficiency is one of the most overlooked reasons people feel cold, and it affects cold tolerance through two separate pathways. The first is anemia: when you don’t have enough iron, your body can’t make adequate red blood cells, which means less oxygen reaches your tissues. Without sufficient oxygen, your cells can’t fuel the metabolic reactions that produce heat. Hemoglobin below 13.6 g/dL in men or 12 g/dL in women qualifies as anemia.
The second pathway is tissue-level iron depletion, which can impair thermoregulation even before full-blown anemia develops. Iron is essential for the enzymes involved in heat production. Research from the National Academies of Sciences found that iron-deficient animals become hypothermic rapidly when exposed to cold, and restoring their red blood cells reverses the problem. In humans, iron deficiency inhibits two key cold-defense mechanisms: the ability to constrict blood vessels near the skin (which keeps warm blood near your core) and the ability to ramp up your metabolic rate to generate extra heat.
If you’re cold all the time and also experiencing fatigue, pale skin, brittle nails, or shortness of breath with mild exertion, iron deficiency is worth investigating. Heavy menstrual periods, vegetarian or vegan diets, and frequent blood donation all increase your risk. A complete blood count and iron panel can give you a clear answer.
Low Body Weight and Body Composition
Your body fat does more than store energy. It acts as insulation. People with lower body fat lose heat to the environment more readily, and their bodies have to work harder to compensate. Research published in the journal Obesity Facts found that people with a normal BMI increased their resting energy expenditure by about 103 calories per day when exposed to mild cold, a meaningful bump in heat production. People with higher BMI didn’t need to increase their metabolic rate at all because their fat layer kept them insulated.
Muscle mass matters too. Muscle is one of the body’s primary heat-generating tissues, both at rest and through shivering. If you’ve lost weight recently, have a naturally slim build, or have lost muscle due to inactivity or aging, you’ll likely notice cold sensitivity more than someone with greater muscle mass. This is one reason older adults tend to feel colder: they typically carry less muscle and have a lower resting metabolic rate.
Circulation Problems and Raynaud’s
If your cold sensitivity concentrates in your fingers and toes rather than your whole body, a circulation issue may be responsible. Raynaud’s phenomenon causes the small blood vessels in your extremities to overreact to cold or stress, clamping down and temporarily cutting off blood flow. During an episode, affected fingers or toes turn white or blue, go numb, and feel intensely cold. As blood flow returns, they may throb, tingle, or flush red. Attacks can last anywhere from a few minutes to several hours.
Primary Raynaud’s, the more common form, has no known underlying cause and is generally more of an annoyance than a danger. Secondary Raynaud’s is triggered by an autoimmune condition like lupus or scleroderma and tends to be more severe, sometimes causing skin ulcers from prolonged poor blood flow. Triggers include grabbing something from the freezer, walking into an air-conditioned building, or even emotional stress.
Nerve Damage Can Distort Temperature Signals
Diabetes, particularly when blood sugar has been poorly controlled over time, can damage the small nerves and blood vessels in your feet and hands. This nerve damage, called peripheral neuropathy, disrupts your body’s ability to sense and respond to temperature. Your feet may feel persistently cold even when they’re objectively warm, because the nerves sending temperature signals to your brain aren’t functioning properly.
High blood sugar weakens the walls of the tiny capillaries that feed your nerves, starving them of oxygen and nutrients. Damaged nerves can also lose the ability to regulate blood flow in your extremities, meaning less warm blood reaches your fingers and toes. Nerve damage can even interfere with how your sweat glands work, further disrupting your body’s temperature control. If you have diabetes and notice cold feet along with numbness, tingling, or a burning sensation, neuropathy is a likely explanation.
Other Factors That Contribute
Vitamin B12 deficiency can cause anemia through a different mechanism than iron deficiency. B12 is essential for red blood cell production, and when levels are low, your body makes fewer and larger red blood cells that don’t carry oxygen as efficiently. The resulting anemia can produce cold sensitivity alongside fatigue, weakness, and numbness or tingling in the hands and feet. People over 50, those on strict plant-based diets, and anyone taking certain acid-reducing medications are at higher risk.
Dehydration reduces your blood volume, which limits how much warm blood your body can circulate to your skin and extremities. Older adults are especially vulnerable because they have a higher threshold for feeling thirsty, lower total body water, and reduced kidney function. Chronic mild dehydration, common in people who simply don’t drink enough throughout the day, can contribute to feeling cold even if it’s not the primary cause.
Sleep deprivation, calorie restriction, and prolonged stress can all lower your core body temperature by slowing metabolism or disrupting hormone levels. Women tend to feel cold more often than men due to lower muscle mass on average and hormonal fluctuations that influence blood vessel dilation, particularly during certain phases of the menstrual cycle.
What Testing Looks Like
If you’re consistently cold in environments where others are comfortable, a few straightforward blood tests can identify or eliminate the most common causes. A thyroid panel (TSH at minimum), a complete blood count to check for anemia, iron studies, and a B12 level cover the majority of treatable conditions. If your results come back normal and you have episodes of color change in your fingers or toes, your doctor may evaluate you for Raynaud’s. If you have diabetes, a nerve conduction study or monofilament test can assess for neuropathy.
Pay attention to whether the cold feeling is all over your body or concentrated in your hands and feet, whether it came on gradually or suddenly, and whether you have other symptoms like fatigue, weight changes, hair loss, or numbness. These details help narrow the list of possible causes considerably and point toward the right testing.