Feeling cold all the time usually signals that your body is producing less heat than it needs or struggling to distribute warmth to your extremities. The most common culprits are an underactive thyroid, iron deficiency, low body mass, poor circulation, and certain medications. Sometimes it’s a combination of factors, and understanding how your body generates and moves heat can help you figure out what’s going on.
How Your Body Produces Heat
Your body generates warmth primarily through your basal metabolic rate, the energy your cells burn just to keep you alive. Muscle tissue is the biggest contributor. People with more lean mass produce more heat at rest and don’t need to activate emergency warming mechanisms until temperatures drop significantly lower. A 2017 study found that larger individuals with more lean mass tolerated colder environments not because of better insulation, but because their bodies generated more baseline heat.
Interestingly, body fat contributes less to keeping you warm than most people assume. The same research found that fat mass had “little contribution to whole-body cold insulation.” What matters more is how much heat your body creates in the first place. That said, people who are significantly underweight often feel cold because they have less of both: less muscle to generate heat and less fat to buffer against temperature swings.
Thyroid Problems and Cold Sensitivity
Your thyroid gland acts as the thermostat for your metabolism. Thyroid hormones regulate resting energy expenditure and are crucial for maintaining core body temperature. When your thyroid is underactive (hypothyroidism), your metabolic rate drops, and your body simply produces less heat.
One specific mechanism involves brown fat, a type of tissue packed with energy-producing structures called mitochondria. Brown fat contains a unique protein that converts stored energy directly into heat, bypassing the normal energy production process. Thyroid hormones activate this system. Research published in Frontiers in Endocrinology demonstrated that cold-induced heat generation is reduced in people with hypothyroidism, and it returns to normal once thyroid hormone levels are restored with treatment.
Other signs of hypothyroidism include fatigue, unexplained weight gain, dry skin, constipation, and brain fog. If cold sensitivity is your main complaint but you also notice several of these, a simple blood test can check your thyroid function.
Iron Deficiency and Anemia
Iron deficiency is one of the most overlooked causes of feeling cold, especially in women of reproductive age. Your red blood cells need iron to carry oxygen, and your tissues need oxygen to produce heat. When hemoglobin levels drop, your body can’t deliver enough oxygen to the muscles and organs responsible for generating warmth.
Animal studies in the American Journal of Physiology confirmed this directly: iron-deficient subjects became unable to maintain normal body temperature in cold environments. The key finding was that the problem was tied specifically to low red blood cell levels rather than just low iron stores in tissues. When red blood cell counts were restored, normal temperature regulation returned.
You might also notice pale skin, fatigue, dizziness, brittle nails, or shortness of breath with mild exertion. Cold hands and feet are often one of the earliest symptoms, appearing before anemia becomes severe enough to cause other obvious problems.
Circulation and Raynaud’s Disease
If your fingers or toes turn white or blue in cold temperatures (or even just when you grab something from the freezer), you may have Raynaud’s disease. This condition causes the small blood vessels supplying your skin to narrow excessively in response to cold or stress. During an episode, affected areas turn pale first, then blue, and feel cold and numb. As blood flow returns, they may turn red, throb, or tingle.
Raynaud’s most commonly affects fingers and toes but can also involve the nose, lips, ears, and nipples. The primary form has no underlying cause and is generally more of a nuisance than a danger. Secondary Raynaud’s, which typically appears around age 40, develops alongside another condition and tends to be more serious.
One red flag worth knowing: if Raynaud’s episodes become severe enough to cause small pits, sores, or permanent tissue damage at your fingertips, this can signal an autoimmune condition called scleroderma. Other warning signs include skin that hardens and tightens (especially on the fingers, hands, feet, and face), small red spots on the hands and face, and calcium deposits under the skin. These symptoms warrant prompt medical evaluation.
Why Women Feel Colder Than Men
If you’re a woman who’s always fighting over the thermostat, physiology is working against you. Men produce significantly more metabolic heat than women, both at rest (90 watts vs. 76 watts in one study) and during physical activity. The difference comes down largely to lean mass: men average about 57 kg of lean tissue compared to roughly 42 kg in women. More muscle means more internal heat production at all times.
Women also tend to have a higher surface area relative to their body mass, which means heat escapes more easily. The combination of generating less heat and losing it faster explains why women consistently report feeling cold in environments where men feel comfortable. Office thermostats, often set based on the metabolic rate of a 40-year-old man, are a classic example of this mismatch.
Medications That Make You Cold
Beta-blockers, commonly prescribed for high blood pressure and heart conditions, are a well-known cause of cold hands and feet. These drugs slow heart rate and reduce the force of each heartbeat, which can decrease blood flow to your extremities. Research has described increased perception of cold hands during beta-blocker treatment as “frequent.” If your cold sensitivity started around the same time you began a new medication, that connection is worth exploring with your prescriber.
Other medications that can contribute include certain antidepressants, blood thinners, and drugs that affect blood vessel tone. Significant calorie restriction or very low-carb diets can also lower your metabolic rate enough to make you noticeably colder.
B12 Deficiency and Nerve Damage
Vitamin B12 deficiency can create a sensation of coldness in your hands and feet, though the mechanism is different from anemia. Low B12 damages peripheral nerves over time, causing numbness and tingling that can feel like coldness even when your skin temperature is normal. This is technically a nerve sensation problem rather than a true temperature regulation issue, but the experience feels the same.
B12 deficiency is more common in people over 50 (who absorb it less efficiently from food), strict vegans, and people taking long-term acid-reducing medications. Left untreated, the nerve damage can become permanent, so persistent tingling or numbness in the hands and feet is worth investigating even if it seems minor.
Sorting Out What’s Causing Your Symptoms
Pay attention to the pattern. Cold sensitivity all over your body, paired with fatigue and weight changes, points toward thyroid or metabolic causes. Cold limited to your hands and feet, especially with color changes, suggests a circulation issue like Raynaud’s. Cold extremities with numbness or tingling could involve B12 deficiency or nerve damage. And if you’re a smaller-framed woman who has always run cold, your baseline physiology may simply produce less heat than average.
A basic blood panel checking thyroid function, iron levels, hemoglobin, and B12 can rule out or confirm the most common medical causes. If your results come back normal, practical strategies like building muscle mass through strength training (which increases your resting metabolic rate), eating enough calories to support your metabolism, and layering clothing strategically can make a real difference in how warm you feel day to day.