Which vitamin deficiencies are linked to hair loss?

When hair starts falling out, many people reach for a hair vitamin. Nutrition does matter for hair, but the link between specific vitamins and hair loss is more complicated than supplement adverts suggest. This guide explains which deficiencies are linked to hair loss, how they are checked and why taking supplements without a test can backfire.

Why nutrition matters for hair

Hair follicles are among the most active cells in the body, so they need a steady supply of energy, protein, vitamins and minerals. When the body is short of nutrients, hair growth may be one of the first things affected ^{1 2}. Very low-calorie or crash diets, rapid weight loss and weight-loss surgery are all associated with telogen effluvium, a temporary increase in shedding ^{3 4 5}.

Iron

Iron deficiency is the most common nutritional deficiency worldwide and is especially common in women with heavy periods, pregnant women and people who eat little meat ^{6 7}. Symptoms of iron deficiency anaemia include tiredness, shortness of breath, pale skin, headaches and hair loss ⁷.

Research suggests a link between low iron stores and some types of hair loss, although studies do not all agree and the exact relationship is still debated ^{8 9}. A blood test for ferritin (stored iron) and a full blood count can show whether your iron is low. If it is, your doctor will look for the reason and may recommend iron supplements. Too much iron can be harmful, so do not take high-dose iron without advice ¹⁰.

Vitamin D

Vitamin D helps keep bones and muscles healthy ¹¹. Several studies have found lower vitamin D levels in people with alopecia areata, telogen effluvium and pattern hair loss than in people without hair loss ¹². This does not prove that low vitamin D causes hair loss, or that taking vitamin D will help. In Malaysia, people who spend most of their time indoors or cover most of their skin may be more likely to have low levels. A doctor can check if needed.

Zinc

Zinc deficiency can cause hair loss, along with skin rashes and poor wound healing, but it is uncommon in people who eat a varied diet ^{13 9}. Taking zinc when you are not deficient is not known to help hair, and too much zinc over a long time may cause other problems.

B vitamins and biotin

Deficiency of vitamin B12 or folate can cause anaemia and tiredness ¹⁴. Biotin is often marketed for hair, but biotin deficiency is rare and there is little evidence that biotin supplements help people who are not deficient. High-dose biotin can also interfere with some laboratory tests, including thyroid and heart tests, so tell your doctor if you take it ¹⁵.

Protein and calories

Not eating enough protein or calories can trigger shedding. This may happen with strict diets, eating disorders or after weight-loss surgery ^{1 4}. If you are trying to lose weight, aim for steady change rather than very rapid loss.

When supplements may harm hair

More is not always better. High intakes of vitamin A and selenium have been associated with hair loss ^{9 1}. Some "hair, skin and nails" supplements combine several of these ingredients. The NHS advises that most people can get the vitamins and minerals they need from a varied and balanced diet, and that taking too much of some supplements can be harmful ¹⁶.

What tests might be done

If you have unexplained shedding, a doctor may consider ^{17 18}:

• Full blood count and ferritin
• Thyroid function tests ¹⁹
• Vitamin D, B12 or folate, depending on your symptoms and diet
• Other tests if your history suggests them

Tests are chosen based on your symptoms, diet and medical history, not as a standard panel for everyone.

Eating for healthy hair

A balanced diet with vegetables, fruit, whole grains, protein foods such as fish, eggs, beans, tofu, lean meat or chicken, and some dairy or alternatives provides most of what hair needs ^{20 21}. Vegetarians and vegans may need to plan carefully for iron and B12.

The bottom line

If you suspect a deficiency, get tested rather than guessing. Correcting a real deficiency may help reduce shedding, but supplements are unlikely to help hair if your levels are normal. If shedding continues, other causes such as female hair loss or pattern hair loss may need to be considered. Our guide on making hair grow faster covers other common questions.

Frequently asked questions

Which vitamin deficiency causes hair loss?

Iron deficiency is the most commonly linked, and low zinc, protein and possibly vitamin D may also be associated with hair loss ^{9 8}.

Should I take hair vitamins?

If you have a proven deficiency, correcting it may help. If your levels are normal, there is little evidence supplements help, and some in high doses may cause hair loss ¹.

What blood test should I ask for hair loss?

Doctors commonly check a full blood count, ferritin and thyroid function, and may check vitamin D, B12 or folate depending on your symptoms ¹⁷.

Can biotin affect blood tests?

Yes. High-dose biotin can interfere with some laboratory tests, so tell your doctor if you take it ¹⁵.

Educational content. Not medical advice.