Feeling cold when others are comfortable has many possible causes. Some are nutritional, the most common being low iron and low vitamin B12. Others have nothing to do with vitamins, such as an underactive thyroid. A simple blood test usually sorts it out.
Iron deficiency (with or without anemia)
Iron is needed to make hemoglobin, which carries oxygen in red blood cells. Low iron is the most common nutrient deficiency worldwide, especially in people with heavy periods (see also safe tampon use overnight), during pregnancy, in vegetarians and vegans, frequent blood donors and people with digestive conditions.
Possible signs: cold hands and feet, fatigue, pale skin, shortness of breath on exertion (sudden or severe breathlessness is different: see what to do about low oxygen levels), brittle nails, headaches, and cravings to chew ice (pica).
Vitamin B12 and folate deficiency
Both are needed to make healthy red blood cells. A shortage causes a type of anemia with larger, fewer red cells, which also leaves you tired and cold. B12 deficiency can also cause tingling in hands and feet, balance problems, a sore tongue and memory changes.
Who is at risk of low B12: older adults, people on a vegan diet without supplements or fortified foods (see vegetarian and vegan eating), people with pernicious anemia, celiac or Crohn’s disease, after weight-loss surgery, and long-term users of metformin or acid-reducing medicines.
Other nutrition-related causes
- Not eating enough overall, or very low body fat: the body produces less heat and conserves energy.
- Low iodine, rare in the US, can affect the thyroid.
Non-vitamin causes to rule out
- Hypothyroidism (underactive thyroid): cold intolerance, weight gain, dry skin, constipation, fatigue. Very common, especially in women.
- Raynaud’s phenomenon: fingers or toes turn white or blue in the cold.
- Poor circulation, diabetes, some medicines (such as beta-blockers), and lack of sleep.
What to ask your doctor
A basic workup often includes a complete blood count (CBC), ferritin (iron stores), vitamin B12 and folate, and thyroid tests (TSH). Mention diet, periods, medicines and digestive symptoms.
Why not just take supplements?
Iron supplements can cause constipation and stomach upset, and too much iron is harmful, particularly for people with hemochromatosis. Taking supplements before testing can also mask the cause: for example, anemia from slow bleeding in the gut needs to be found, not just treated. Once a deficiency is confirmed, your doctor will advise the right form and dose.
Food sources
- Iron: red meat, poultry, fish, beans, lentils, tofu, fortified cereals. Vitamin C foods help absorb plant iron.
- B12: meat, fish, eggs, dairy, fortified plant milks and nutritional yeast.
- Folate: leafy greens, beans, citrus, fortified grains.
The NIH Office of Dietary Supplements has detailed fact sheets on iron and vitamin B12.
