Feeling cold all the time usually signals that your body is either producing less heat than it should, losing heat faster than average, or struggling to circulate warm blood to your extremities. Sometimes it’s as simple as body composition or being female. Other times, it points to a treatable medical condition like thyroid dysfunction, anemia, or poor circulation. Understanding the most common causes can help you figure out which one fits your situation.
Your Thyroid Sets Your Internal Thermostat
The single most common medical cause of constant coldness is an underactive thyroid. Thyroid hormones regulate your body’s energy expenditure and heat production. When your thyroid isn’t making enough of these hormones, your basal metabolism slows down, and you produce less “obligatory thermogenesis,” the baseline heat your body generates just by being alive. Normally, this background heat production is enough to keep you comfortable at room temperature (roughly 73 to 91°F). With hypothyroidism, that baseline drops, and you start feeling chilled in environments other people find perfectly comfortable.
Beyond baseline heat, your body has a backup system for cold environments: shivering and fat-burning in specialized brown fat tissue. Hypothyroidism impairs these backup mechanisms too, making it harder to warm up once you get cold. If your persistent coldness comes with fatigue, unexplained weight gain, dry skin, or thinning hair, a simple blood test measuring TSH (thyroid-stimulating hormone) can confirm or rule this out. The normal TSH range is 0.4 to 4.0 mIU/L, and values above that range suggest your thyroid is underperforming.
Iron and B12 Deficiency Starve Your Cells of Oxygen
Your red blood cells carry oxygen to tissues throughout your body, and that oxygen delivery is a key part of heat production. When you’re low on iron, you don’t make enough functional red blood cells to keep up. The result is anemia, and one of its hallmark symptoms is feeling cold, particularly in your hands and feet. Iron deficiency anemia is diagnosed by checking hemoglobin levels (normal is roughly 13.2 to 16.6 g/dL for men and 11.6 to 15.0 g/dL for women) along with ferritin, a protein that reflects your iron stores.
Vitamin B12 plays a similar role. Without enough B12, your body can’t produce adequate healthy red blood cells, leading to a different type of anemia with the same chilling effect. B12 deficiency tends to cause coldness specifically in the hands and feet, along with numbness, tingling, fatigue, and sometimes balance problems. Vegetarians, vegans, older adults, and people with digestive conditions that impair absorption are at higher risk.
Women Run Colder Than Men
If you’re a woman who’s always reaching for a sweater while the men around you seem fine, there’s solid physiology behind that. Women tend to have lower resting metabolic rates than men at every temperature, which means less internal heat production. One analysis found that traditional metabolic rate assumptions, based on male physiology, may overestimate female metabolic rates by as much as 35%.
The differences go beyond metabolism. Women generally have less total body mass but a higher surface-area-to-mass ratio, which means heat escapes faster relative to what’s being produced. Women also have lower blood flow rates to the extremities, so their capacity for keeping hands and feet warm is reduced compared to men. Cold exposure leads to a greater drop in skin temperature for women, especially in the fingers and toes. This isn’t a disorder. It’s normal physiology, but it explains why office thermostats set for male comfort can leave women genuinely uncomfortable.
Circulation Problems and Raynaud’s
If your cold sensitivity is concentrated in your fingers and toes, and you notice dramatic color changes in those areas, you may have Raynaud’s phenomenon. During an episode, blood vessels in the extremities constrict sharply in response to cold or stress. The affected skin first turns white as blood flow drops off, then blue as oxygen depletes, then red and throbbing as circulation returns. Some people also experience Raynaud’s in the nose, lips, ears, and nipples.
Raynaud’s affects roughly 3 to 5% of the population, and most cases are “primary,” meaning they occur on their own without an underlying disease. Episodes are triggered by cold temperatures, handling frozen items, air conditioning, or emotional stress. The numbness and stinging pain during rewarming can range from mildly annoying to disruptive enough to affect daily tasks. Secondary Raynaud’s, which is linked to autoimmune conditions, tends to be more severe and typically appears after age 30.
Medications That Reduce Blood Flow
Certain medications can make you feel colder by constricting blood vessels in your extremities. Beta-blockers, commonly prescribed for high blood pressure and heart conditions, are the most well-known culprits. These drugs reduce blood flow to the arterioles, the small blood vessels where the greatest drop in blood pressure occurs and where peripheral resistance is highest. The result is cold hands and sometimes full Raynaud’s-like symptoms. Studies have found that patients on beta-blockers report cold hand symptoms more frequently than those on other blood pressure medications, driven by heightened vasoconstriction and a decreased ability of blood vessels to dilate.
If you started feeling persistently cold after beginning a new medication, that connection is worth exploring with your prescriber. Other drug classes that can contribute include certain migraine medications, stimulant-based ADHD treatments, and some decongestants.
Diabetes and Nerve Damage
Diabetes can cause coldness in the feet and lower legs through a less obvious mechanism: nerve damage. High blood sugar over time injures the smallest nerve fibers first, particularly the thin, unmyelinated fibers that play a key role in temperature regulation. These fibers normally signal blood vessels in the feet to dilate when your body needs to redistribute heat. When they’re damaged, your feet lose the ability to properly regulate their own temperature.
Research from the American Diabetes Association found that people with diabetes had impaired ability to dilate blood vessels in the feet, even those who hadn’t yet been diagnosed with clinical neuropathy. This means the thermoregulatory problem can appear earlier than the more recognized neuropathy symptoms like numbness and tingling. If you have diabetes and your feet consistently feel cold, it may be an early sign of microvascular changes worth monitoring.
Body Composition and Muscle Mass
Your body’s ability to generate and retain heat depends partly on how much muscle and fat you carry. Muscle tissue is metabolically active and produces heat even at rest, so people with very low muscle mass generate less warmth. Interestingly, research on body fat tells a more nuanced story than you might expect. One study comparing people with about 11% body fat to those around 24% found no significant difference in core temperature or metabolic rate between the groups. Fat provides some insulation, but it’s not the primary driver of feeling warm or cold.
What does matter is the combination of low fat and low muscle. People with both low body fat and low muscle mass tend to prefer warmer environments. This is common in older adults who’ve lost muscle over the years, people who are significantly underweight, and those recovering from illness. If you’ve recently lost a lot of weight, whether intentionally or not, that alone can explain a new sensitivity to cold.
Other Contributing Factors
Dehydration reduces blood volume, which limits how effectively your body circulates warm blood to the skin and extremities. Most people don’t think of water intake when they feel cold, but even mild dehydration can contribute. Sleep deprivation also plays a role: your body regulates temperature partly through sleep cycles, and chronic poor sleep disrupts that process.
Calorie restriction is another underappreciated cause. When you eat significantly less than your body needs, your metabolism slows as a conservation strategy, and heat production drops along with it. This is common in people who are dieting aggressively, those with eating disorders, and older adults who’ve gradually reduced their food intake. If you’re eating less than usual and feeling colder than usual, the two are likely connected.
Figuring Out Your Cause
Start by noticing the pattern. Coldness concentrated in your hands and feet, especially with color changes, points toward Raynaud’s or circulation issues. Whole-body coldness with fatigue and weight changes suggests thyroid function worth checking. Coldness that arrived alongside a new medication, a change in diet, or significant weight loss has an obvious starting point. Coldness in the feet alone, particularly if you have diabetes, may signal early nerve involvement.
A basic blood panel covering thyroid function, iron, ferritin, B12, and blood sugar can rule out or confirm the most common medical causes. These are inexpensive, widely available tests, and if one of them comes back abnormal, treatment often resolves the cold sensitivity within weeks to months. If your results are normal and you’re a woman with a smaller frame, the explanation may simply be physiology doing exactly what it’s designed to do, just at a lower thermostat setting than the people around you.