Which Vitamin Deficiency Causes Hair Loss?

If you're losing more hair than usual, a vitamin deficiency might be to blame. Your hair needs certain nutrients to grow healthy and strong. When your body lacks these vitamins and minerals, hair can become thin, brittle, and fall out.

The good news? Once you identify which vitamin deficiency causes hair loss in your case, treatment can often help your hair grow back.

Key Vitamins Linked to Hair Loss

Vitamin D

Vitamin D helps create the tiny pores (follicles) where hair grows. Research shows that about 50% of people with hair loss have low vitamin D levels. Studies also find a strong link between vitamin D deficiency and alopecia areata, a condition where hair falls out in patches.

Iron

Iron carries oxygen to your hair follicles so hair can grow. Women with hair loss often have lower iron levels than those without. Heavy periods, pregnancy, and certain diets can lead to iron deficiency.

Biotin (Vitamin B7)

Biotin helps your body make keratin, the protein that forms hair. While true biotin deficiency is rare, one study found 38% of women with hair loss had low biotin levels. Signs include brittle nails and skin rashes alongside thinning hair.

Vitamin B12

Low B12 means fewer red blood cells to deliver oxygen to your hair. This can slow hair growth and cause shedding. Vegetarians and older adults are at higher risk for B12 deficiency.

How to Stop Hair Loss from Vitamin Deficiency

The first step is getting tested. A simple blood test can check your vitamin D, iron, and B12 levels. Don't start supplements without knowing which nutrients you actually need.

If tests show a deficiency, your doctor can recommend the right supplement dose. For vitamin D, this is often 2,000-4,000 IU daily. Iron supplements should only be taken if you're truly deficient, as too much iron can be harmful.

Eating nutrient-rich foods also helps. Include eggs, fish, leafy greens, and lean meats in your diet. Most people see improvement within 3 to 6 months of treating the deficiency.

Important Warnings

More is not better with supplements. Too much vitamin A, selenium, or vitamin E can actually cause hair loss. Taking high doses of any supplement without medical guidance can be harmful.

Vitamin deficiencies are rarely the only cause of hair loss. Stress, hormones, genetics, and thyroid problems can all play a role. If treating a deficiency doesn't help after several months, talk to a dermatologist about other possible causes.