Feeling cold when others around you seem comfortable usually signals that your body is producing less heat, losing heat faster, or struggling to circulate warm blood to your extremities. The causes range from everyday factors like not eating enough or poor sleep to underlying conditions like thyroid problems and anemia. Understanding the most common reasons can help you figure out whether your persistent chill is something to address on your own or worth bringing up with a doctor.
Your Thyroid May Be Underperforming
The thyroid gland controls your metabolism, which is essentially the rate at which your body converts food and oxygen into energy and heat. When the thyroid slows down, a condition called hypothyroidism, every system in your body dials back. You produce less internal heat, and cold intolerance is one of the earliest and most noticeable symptoms.
In hypothyroidism, the thyroid doesn’t produce enough of its two key hormones, so the pituitary gland in your brain keeps sending stronger signals (measured as TSH) trying to compensate. A normal TSH level falls between 0.45 and 4.5 mU/L. When TSH climbs above that range but other thyroid levels still look normal, you have what’s called subclinical hypothyroidism, which can still cause cold sensitivity, fatigue, and weight gain even though it’s considered a mild form. Women, people over 60, and those with a family history of thyroid disease are at the highest risk.
Low Iron or B12 Starves Your Cells of Oxygen
Iron-deficiency anemia is one of the most common nutritional causes of feeling cold. Iron is essential for making hemoglobin, the molecule in red blood cells that carries oxygen throughout your body. When iron is low, your bone marrow can’t produce enough hemoglobin, and without adequate oxygen delivery, your tissues generate less heat. Pale skin and cold hands and feet are hallmark signs.
Vitamin B12 plays a similar role. Your body needs B12 to make red blood cells, so a deficiency leads to its own form of anemia. The result is the same: fewer healthy red blood cells, less oxygen reaching your tissues, and a body that struggles to stay warm. B12 deficiency is particularly common in people who eat little or no animal products, those over 50 (who absorb B12 less efficiently), and people with digestive conditions that affect nutrient absorption.
You’re Not Eating Enough
Severely cutting calories forces your body to conserve energy, and one of the first things it sacrifices is heat production. A controlled trial published in JAMA found that after six months of calorie restriction, participants experienced a measurable drop in core body temperature. Their metabolic rate fell roughly 6% more than expected from weight loss alone, meaning the body was actively slowing down its engine beyond what losing mass would explain. This metabolic adaptation is why people on very low-calorie diets often feel persistently cold, especially at night.
Even moderate undereating can have this effect if it continues long enough. Your body treats a sustained calorie deficit as a signal that fuel is scarce and responds by reducing thermogenesis, the process of generating heat. If you’ve recently started a restrictive diet and notice you’re reaching for sweaters more often, your calorie intake may be too low.
Poor Sleep Makes You Feel Colder
Sleep and temperature regulation share the same brain circuitry, so disrupting one disrupts the other. Research at Washington University found that sleep-deprived animals consistently sought out warmer environments, a pattern that mirrors what happens in people. Even fragmented sleep, being woken frequently without full deprivation, produced the same preference for warmth.
The connection appears to be hardwired. The neurons that regulate sleep also regulate temperature preference, which means chronic poor sleep can genuinely shift how cold your body feels. If you’ve been sleeping badly and feeling unusually chilly during the day, addressing the sleep problem may also fix the temperature issue.
Raynaud’s Phenomenon
If your fingers or toes turn white, then blue, then red when exposed to cold or stress, you likely have Raynaud’s phenomenon. During an episode, the small blood vessels in your extremities spasm and temporarily cut off blood flow. The affected area goes pale from lack of blood, turns blue as remaining blood loses oxygen, then flushes red and may throb or tingle as circulation returns. Episodes can last minutes to hours.
The primary form has no known cause and is the more common version. It’s uncomfortable but generally harmless. The secondary form is linked to autoimmune diseases like lupus or scleroderma and tends to be more serious because it involves actual damage to the blood vessels over time. Triggers include grabbing a cold drink, reaching into a freezer, walking into air conditioning on a warm day, emotional stress, and smoking or vaping.
Body Composition and Heat Production
Your body fat and muscle mass both play direct roles in how warm you feel. Subcutaneous fat, the layer just beneath your skin, acts as insulation between your core and the outside environment. Research published in PNAS describes this layer as a heat-producing tissue that prevents a temperature gradient from forming between your skin surface and your organs, essentially keeping warmth from leaking out. People with very low body fat lose heat faster and feel cold more easily.
Muscle tissue is also a major source of heat. Even at rest, muscle burns calories and generates warmth. People with less muscle mass, whether from a sedentary lifestyle, aging, or illness, produce less baseline heat. This is one reason older adults tend to feel colder: they lose both subcutaneous fat and muscle over time. As MedlinePlus notes, the decrease in fat below the skin that comes with aging makes it harder to maintain warmth.
Diabetes and Nerve Damage
Diabetic neuropathy, nerve damage caused by prolonged high blood sugar, can make your feet feel cold even when they’re objectively warm. The damage works on multiple levels. It impairs your ability to sense temperature accurately, so your brain receives distorted signals. It also weakens the walls of the tiny blood vessels (capillaries) that supply your nerves with oxygen, compounding the problem. On top of that, nerve damage can disrupt how your sweat glands function, which interferes with your body’s overall ability to regulate temperature.
Cold feet from neuropathy are different from cold feet caused by poor circulation alone. With neuropathy, the sensation of coldness may be accompanied by numbness, tingling, or a reduced ability to feel pain. Smoking worsens the issue by narrowing arteries and further restricting blood flow to the legs and feet.
Dehydration and Blood Volume
Water makes up a significant portion of your blood volume, and when you’re dehydrated, that volume drops. With less blood circulating, your body prioritizes sending warm blood to your vital organs and pulls it away from your skin and extremities. The result is cold hands, cold feet, and a general sense of being chilled. Dehydration also compromises your body’s broader ability to regulate temperature, making you more sensitive to environmental changes. Most people don’t connect feeling cold with not drinking enough water, but mild chronic dehydration is surprisingly common and easy to fix.
Sorting Out the Cause
If you’ve always run cold, body composition and genetics are the most likely explanations. If the cold sensitivity is new or worsening, it’s worth considering what else has changed. A new diet, poor sleep, or not drinking enough water are the simplest fixes. Persistent, unexplained cold intolerance, especially paired with fatigue, weight changes, or pale skin, points toward thyroid function, anemia, or a B12 deficiency, all of which show up on routine blood work. Cold that’s concentrated in your fingers and toes with visible color changes suggests Raynaud’s, while cold feet with numbness in someone with diabetes points toward neuropathy.