Encyclopedia · supplement
Vitamin B12
A real but uncommon cause of hair loss when deficient, with no evidence that extra B12 helps hair if your levels are normal.
What it is
A water-soluble vitamin found only in animal foods and fortified foods, needed for DNA synthesis and red blood cells. Deficiency is most common in vegans who do not supplement, older adults, people with pernicious anemia or gut or weight-loss surgery, and long-term users of metformin or acid-suppressing drugs.
How it works
Follicle cells divide fast and need B12 for DNA synthesis. Severe deficiency can disturb hair growth and pigment.
What the studies show
- In 90 women with chronic telogen effluvium versus 90 controls, B12 (and ferritin and vitamin D) did not differ. Durusu Turkoglu 2024
- A meta-analysis of 18 studies (2,538 people) found 57% had hair loss after weight-loss surgery. Low folate and ferritin were tied to loss, but low B12 and iron were not. Zhang 2021
- In a case series of 71 people with premature graying, low B12 and hypothyroidism were associated with early graying, and 90% had a family history. Sonthalia 2017
- A review found the role of B vitamins in alopecia unclear and called for large placebo-controlled trials. Almohanna 2019
Whether treating borderline-low (not frank deficiency) B12 changes shedding or graying has not been tested in a controlled trial we found.
How it's used in studies
Oral or injected B12 treats confirmed deficiency.
Side effects and safety
European authorities found no defined adverse effects and set no upper limit.
Bottom line
Consider a B12 test if you are vegan, over 50, on metformin, have gut disease, or have unexplained shedding or early graying. Low B12 with early graying is a correctable association, not proof of cause. Skip megadose "hair" B12. Discuss with a doctor.
Studies 4
Durusu Turkoglu IN et al. A comprehensive investigation of biochemical status in patients with telogen effluvium: Analysis of Hb, ferritin, vitamin B12, vitamin D, thyroid function tests, zinc, copper, biotin, and selenium levels. 2024
Result: Only zinc (lower) and selenium (higher) differed; ferritin, B12, vitamin D, biotin and hemoglobin did not.
Read the study ↗Zhang W et al. Hair Loss After Metabolic and Bariatric Surgery: a Systematic Review and Meta-analysis. 2021
Result: Hair loss in 57%; lower folic acid (SMD -0.88), ferritin and borderline zinc associated with loss; B12 and iron were not.
Read the study ↗Sonthalia S et al. Demographic Characteristics and Association of Serum Vitamin B12, Ferritin and Thyroid Function with Premature Canities in Indian Patients from an Urban Skin Clinic of North India: A Retrospective Analysis of 71 Cases. 2017
Result: Low B12 and hypothyroidism associated with early graying; 90% had a family history.
Read the study ↗Almohanna HM et al. The Role of Vitamins and Minerals in Hair Loss: A Review. 2019
Result: Vitamin and mineral deficiency may be a modifiable factor in hair loss, but well-designed trials are lacking.
Read the study ↗Related
- Folate (vitamin B9)A B vitamin that is sometimes low in people with hair loss, but not a hair-growth supplement if your levels are normal.
- Iron and ferritinLow iron stores are common in people who shed hair, but no trial has shown that iron pills regrow hair, and nobody agrees on a hair-specific ferritin target.
- Diet and hairCrash diets and rapid weight loss cause shedding, ordinary diets rarely do, and testing beats guessing before you buy supplements.