Hair Falling Out? Vitamins and Deficiencies to Check

Hair loss can be associated with low levels of vitamin D, biotin, vitamin B12, or folate, but there is no single deficiency responsible for every case. Iron deficiency is also a common nutritional contributor, although iron is a mineral rather than a vitamin. Ask a healthcare professional for blood tests before taking high-dose supplements.

Vitamin D supports normal hair-follicle activity, and low levels have been observed in some people with diffuse shedding or alopecia areata. A clinician can order a 25-hydroxy vitamin D blood test and recommend a dose based on the result rather than guesswork.

True biotin deficiency may cause thinning hair, brittle nails, or a skin rash, but it is rare in people eating a varied diet. Avoid taking large biotin doses without guidance because they can interfere with thyroid, hormone, and cardiac laboratory tests; tell your clinician about any biotin product before testing.

Low iron stores can contribute to shedding, particularly after heavy menstrual bleeding, restrictive dieting, or pregnancy. Request a complete blood count and ferritin test, while vitamin B12 and folate testing may be appropriate for vegans, people with absorption disorders, or anyone taking certain medications.

Sudden shedding can also follow illness, surgery, childbirth, rapid weight loss, thyroid changes, or severe stress. Arrange an evaluation if hair falls out in patches, the scalp is painful or inflamed, or shedding continues for more than three months; our science-backed guide to hair loss and nutrient deficiencies explains the common tests and nutritional factors in greater depth.