People feel cold when their body loses heat faster than it produces it, or when something disrupts the internal systems that regulate temperature. Your body works constantly to maintain a core temperature around 37°C (98.6°F), and feeling cold is the signal that this balance is under strain. The reasons range from simple environmental exposure to underlying health conditions, body composition, hydration, and even how well you slept last night.
How Your Body Controls Temperature
A small region deep in your brain called the preoptic area acts as your internal thermostat. It receives signals from temperature sensors in your skin and also monitors the warmth of the blood flowing through the brain itself. When those signals indicate you’re cooling down, this region triggers a cascade of heat-saving responses throughout your body.
The first line of defense is vasoconstriction: your sympathetic nervous system tells the muscles wrapped around blood vessels near your skin to tighten, narrowing the vessels and reducing blood flow to your surface. Less blood at the skin means less heat escaping into the air. This is why your hands, feet, nose, and ears get cold first. They’re the places where your body deliberately sacrifices warmth to protect your core.
If vasoconstriction isn’t enough, your body starts generating extra heat. Shivering is the most obvious version of this. Your muscles contract rapidly and involuntarily, converting stored energy into warmth. You also have a quieter system: specialized fat tissue (brown fat) that burns calories purely to produce heat without any muscle movement at all. This process relies on a protein in the fat cells that essentially short-circuits normal energy production, releasing heat instead of storing it as usable fuel.
Why Some People Feel Cold More Than Others
Body Size and Composition
Subcutaneous fat, the layer of fat just beneath your skin, acts as insulation. In cold-water immersion studies, people with higher body fat can maintain their core temperature in water as cold as 12°C, while some lean individuals begin cooling progressively even at 25 to 29°C. That’s a dramatic gap. Fat insulates the trunk especially well, and in combination with muscle mass in the limbs, it forms a barrier that slows heat loss. Smaller people also have a higher surface-area-to-volume ratio, meaning more skin relative to the body’s heat-producing mass, so they lose warmth faster.
Metabolic Rate
Your resting metabolic rate determines how much heat your body generates at baseline. People with higher lean mass produce more heat simply by existing. A 2024 study published in PNAS found that women have a significantly lower average resting metabolic rate than men, which directly correlates with body size, weight, and lean mass. This means women’s bodies produce less baseline heat, and their thermoneutral zone (the range of temperatures where the body doesn’t have to work to stay warm) shifts lower, resembling what the researchers called an “arctic” shift compared to men.
Interestingly, the same study found no significant difference in how men and women actually perceived thermal comfort across a range of temperatures. Women’s bodies may work differently to maintain warmth, but the subjective experience of “feeling cold” was comparable once you account for the temperature range. The real difference is physiological, not perceptual.
Medical Conditions That Cause Cold Sensitivity
Hypothyroidism
Your thyroid gland is one of the major regulators of metabolism and heat production. When it’s underactive, it doesn’t produce enough thyroid hormones, and your metabolic rate drops. The result is less internal heat generation, which makes you feel cold even in environments that don’t bother other people. Cold intolerance is one of the hallmark symptoms of hypothyroidism, alongside fatigue, weight gain, and dry skin. A simple blood test can identify it.
Iron-Deficiency Anemia
When you don’t have enough healthy red blood cells, your body can’t deliver oxygen efficiently to the tissues that produce heat. Research in the American Journal of Physiology demonstrated that anemia’s effect on temperature regulation is tied directly to reduced oxygen delivery rather than low iron in the tissues themselves. When researchers corrected the red blood cell count through transfusion, normal temperature regulation returned.
Anemia also compromises your thyroid hormone response to cold. There’s a significant positive correlation between red blood cell levels and the body’s ability to ramp up thyroid hormones during cold exposure. So anemia hits you twice: less oxygen for heat production and a blunted hormonal response to cold stress.
Raynaud’s Phenomenon
Some people experience an exaggerated version of the normal vasoconstriction response. In Raynaud’s, the nerves controlling blood vessel width in the fingers and toes overreact to cold or stress, causing severe narrowing that can turn affected areas white, then blue, then red as blood flow returns. It’s more than just cold hands. The blood supply essentially shuts off temporarily. Primary Raynaud’s happens on its own, while secondary Raynaud’s is linked to autoimmune or connective tissue conditions. Doctors can distinguish between them by examining the tiny blood vessels at the base of your fingernails under magnification, looking for swelling or structural changes.
Lifestyle Factors That Make You Feel Cold
Poor Sleep
Sleep deprivation disrupts the coordination of blood flow throughout your body. Normally, the small fluctuations in blood flow to your hands and feet move in sync, keeping your extremities at a stable temperature. When you’re sleep-deprived, this coordination breaks down. Blood flow to your hands and feet can move in opposite directions: when your feet warm up, your hands cool down, and vice versa. This “uncoupling” effect had never been documented before recent research identified it. The practical result is that parts of your body feel uncomfortably cold even when your overall temperature is normal.
Dehydration
Water makes up roughly 60% of your body mass, and your blood plasma is a critical part of that. When you’re dehydrated, plasma volume drops. Even a 2 to 5% reduction in body mass from water loss can slash plasma volume by 10% or more and total blood volume by at least 6%. With less blood circulating, your heart has to work harder. Stroke volume drops, heart rate rises to compensate, and cardiac output falls. Your body becomes less effective at distributing warmth through circulation. While most dehydration research focuses on heat stress during exercise, the underlying principle applies in everyday life: inadequate hydration means less efficient blood flow and less effective temperature regulation.
Smoking and Vaping
Nicotine causes blood vessels to tighten, which directly lowers skin temperature. Smoking, vaping, and even secondhand smoke exposure all trigger vasoconstriction. This mimics and amplifies the body’s natural cold response, leaving you with colder extremities than you’d otherwise have.
Not Eating Enough
Your body generates heat as a byproduct of digesting and metabolizing food, a process called diet-induced thermogenesis. If you’re eating too little, particularly on very low-calorie diets, your body has less fuel to burn and may lower your metabolic rate to conserve energy. The result is less heat production and a persistent feeling of being cold.
Age and Cold Sensitivity
Older adults tend to feel cold more easily for several compounding reasons. Metabolic rate naturally declines with age as muscle mass decreases. The body’s total water content also shifts with age, affecting circulation efficiency. Blood vessels become less responsive, making vasoconstriction and vasodilation slower and less precise. The temperature-sensing neurons in the brain may also become less sensitive over time, meaning the body is slower to detect and respond to drops in temperature. All of these changes mean an older person can lose significant body heat before their warming mechanisms fully kick in.
When Feeling Cold Signals Something Deeper
Occasional coldness in a chilly room is normal thermoregulation doing its job. Persistent cold sensitivity that’s new for you, or that others around you don’t share, is worth paying attention to. The most common treatable causes are thyroid dysfunction and iron-deficiency anemia, both detectable with routine blood work. Circulatory conditions like Raynaud’s are identifiable through their distinctive pattern of color changes in the fingers or toes. Diabetes, peripheral artery disease, and certain autoimmune conditions can also impair circulation or nerve function enough to produce chronic cold sensitivity. If you’re consistently colder than you used to be, or colder than seems reasonable for the environment, that pattern itself is useful information for a doctor to evaluate.