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 skin and extremities. The causes range from simple and fixable, like not eating enough or being low on iron, to medical conditions that need treatment. Normal body temperature actually averages closer to 97.9°F rather than the old 98.6°F standard, based on an analysis of over 618,000 temperature readings from Stanford Health Care. So running a bit “cool” can be normal, but persistent, bothersome coldness typically has an identifiable reason.
Your Thyroid Sets the Thermostat
The most common medical cause of feeling cold all the time is an underactive thyroid. Thyroid hormones act like a metabolic dial for nearly every cell in your body. They drive the chemical reactions that convert food into energy and heat, promote the creation of new mitochondria (the tiny power generators inside cells), and even cause controlled “leaks” across cell membranes that force cells to burn extra fuel just to maintain their normal electrical balance. All of that activity produces heat as a byproduct.
When thyroid hormone levels drop, this entire system slows down. Your cells make fewer mitochondria, burn less fuel, and generate less heat. One particularly important effect: thyroid hormones normally divert some of the energy stored in mitochondria directly into heat rather than letting it all go toward powering the cell. Without enough thyroid hormone, that heat-generating shortcut stalls. The result is a lower resting metabolic rate and a body that simply doesn’t produce enough warmth. Other signs of low thyroid include fatigue, weight gain, dry skin, and constipation. A simple blood test can confirm it.
Low Iron Impairs Heat Production
Iron deficiency is one of the most overlooked causes of cold intolerance, and you don’t need to be severely anemic for it to matter. Iron-deficient people have measurable difficulty maintaining body temperature in cool air (around 61°F) or cool water (around 82°F) compared to people with normal iron levels and similar body composition.
Iron plays a dual role here. First, low iron means fewer healthy red blood cells carrying oxygen to your tissues. Without adequate oxygen, your body can’t ramp up its metabolic rate to generate heat, and it also struggles with vasoconstriction, the process of narrowing blood vessels near the skin to keep warmth inside your core. Second, iron itself is needed in the tissues for enzymes involved in heat production, separate from its role in red blood cells. Research in animals has shown that simply correcting anemia with a blood transfusion restores the ability to stay warm, and it also restores the normal thyroid response to cold exposure. In other words, low iron can sabotage your thyroid’s ability to respond to cold even if your thyroid is otherwise healthy.
Women with heavy periods, vegetarians, frequent blood donors, and endurance athletes are all at higher risk. Symptoms beyond cold intolerance include fatigue, pale skin, brittle nails, and shortness of breath with exertion.
Not Eating Enough Lowers Core Temperature
Your body treats calories as both fuel and furnace material. When calorie intake drops significantly, one of the first energy-saving moves is to reduce core body temperature. In controlled studies, animals fed 50% of their normal caloric intake showed a core temperature drop of about 0.77°C (roughly 1.4°F). That temperature suppression persisted even after refeeding began, staying about 0.27°C below normal during the weight-regain phase.
This isn’t limited to extreme dieting. Chronic under-eating, skipping meals regularly, or following very restrictive diets can trigger the same conservation response. Your body essentially decides that generating heat is a luxury it can’t afford. If you’ve recently cut calories and notice you’re reaching for a sweater more often, the two are likely connected.
Poor Circulation and Raynaud’s
Sometimes the problem isn’t that your body is cold overall, but that warmth isn’t reaching your hands, feet, nose, or ears. In Raynaud’s phenomenon, the small blood vessels supplying the skin go into spasm when exposed to cold or stress, drastically limiting blood flow. Affected fingers or toes may turn white, then blue, then red as blood flow returns, often with numbness, tingling, or pain.
Primary Raynaud’s is the more common form and isn’t tied to another disease. It’s essentially an exaggerated version of the normal response to cold. Secondary Raynaud’s develops alongside autoimmune conditions like lupus or scleroderma and tends to be more severe. Over time, the small blood vessels can thicken, further restricting flow even between episodes.
Certain medications can trigger or worsen this pattern. Beta-blockers (commonly prescribed for high blood pressure), some chemotherapy drugs, and stimulants including ADHD medications and even over-the-counter decongestants containing pseudoephedrine are all associated with Raynaud’s-like symptoms. If your hands or feet started feeling cold after beginning a new medication, that connection is worth exploring with your prescriber.
Stress and Anxiety Pull Blood Inward
The fight-or-flight response is designed to prepare you for physical danger, and part of that preparation involves redirecting blood away from your skin and extremities toward your heart, lungs, and muscles. When your sympathetic nervous system fires, it releases adrenaline, which constricts blood vessels in your hands and feet. The result: cold, sometimes clammy fingers and toes.
For people with chronic anxiety or high stress levels, this response can activate frequently throughout the day, keeping extremities persistently cool. It’s not dangerous, but it can be uncomfortable and disorienting, especially if you don’t realize the connection between your mental state and your body temperature.
B12 Deficiency and Nerve Damage
Vitamin B12 keeps both your red blood cells and your nerve cells healthy. A deficiency can cause anemia (reducing oxygen delivery and heat production, much like iron deficiency) and also damage the peripheral nerves in your hands and feet. That nerve damage can show up as numbness, tingling, or an abnormal sensation of coldness even when your skin temperature is normal.
Diabetes creates a similar problem through a different path. Diabetic peripheral neuropathy damages the small nerve fibers that detect temperature, so you may feel cold in your feet or hands because the nerves are misfiring rather than because blood flow has changed. Autonomic neuropathy from diabetes can also disrupt your sweat glands, making it harder for your body to regulate temperature in either direction.
In both cases, the sensation of cold is real to you, but the underlying issue is nerve function rather than actual heat loss.
Sleep Loss Disrupts Temperature Control
The same neurons in your brain that regulate sleep also regulate body temperature. Research at Washington University has confirmed that these dual-purpose neurons link the two systems so tightly that disrupting one inevitably affects the other. Chronic sleep deprivation or irregular sleep schedules (sometimes called “social jet lag”) alter how your brain manages its internal thermostat.
Poor sleepers often notice they feel colder during the day, and their body temperature rhythms become flatter, losing the normal warming peak that occurs in late afternoon. Improving sleep consistency can help restore more normal temperature regulation over time.
Body Composition and Individual Variation
Some people simply run cold, and body composition is a major factor. Body fat acts as insulation, and people with less of it lose heat faster through the skin. Muscle tissue generates heat at rest, so less muscle mass also means less baseline warmth. Smaller body frames have a higher surface-area-to-volume ratio, meaning they radiate heat more efficiently relative to how much heat they produce. This is one reason women, who on average have smaller frames and higher body fat percentages in different distributions, tend to report feeling cold more often than men.
Stanford researchers found that age, sex, height, weight, and time of day together account for about 25% of the variability in any one person’s normal temperature. So a naturally lower baseline doesn’t necessarily indicate a problem. The question is whether your cold feeling is new, worsening, or accompanied by other symptoms like fatigue, weight changes, or numbness. Those patterns point toward something treatable rather than just individual variation.