Vitamin B12 and hair loss: who is at risk and what testing shows

Vitamin B12 is one of the blood tests people most often ask about when their hair starts to fall. It sits on many "hair loss panels", it appears in hair supplements, and B12 injections are sometimes offered as a general pick-me-up. The real picture is more modest. B12 deficiency is a genuine medical problem that is worth finding, especially in people at higher risk. But studies of people with hair loss have mostly not found that their B12 levels differ from those of people without hair loss, and there is not enough evidence to recommend B12 supplements for hair loss in people who are not deficient. This guide explains who is at risk, what the tests show, and what a low result does and does not mean for your hair.

(This is general information, not personal medical advice.)

Short answer

Vitamin B12 is needed to make DNA and red blood cells and to keep the nervous system healthy ^{1 2}. Deficiency can cause anaemia, tiredness, a sore or red tongue, numbness or tingling, and problems with memory and mood ². A dermatology review lists hair changes among the skin signs of B12 deficiency ³, and B12 deficiency has been linked to premature greying ⁴. But for common hair loss, the evidence is thin. Several studies of alopecia areata and telogen effluvium found no difference in B12 levels between people with hair loss and controls ^{1 5}, and a major review concluded that there is not enough data to recommend B12 screening or supplements for hair loss ¹. Testing makes sense if you are at risk: you eat little or no animal food, are older, take metformin or acid-reducing medicines, have had stomach surgery, or have a gut or autoimmune condition ^{6 7}. If B12 is low, the priority is to find the cause and treat it properly.

What vitamin B12 does

Vitamin B12, also called cobalamin, is a water-soluble vitamin. It is a cofactor in the production of DNA, RNA and proteins, and it is essential for red blood cell formation and nerve function ¹. The body cannot make it, so it must come from food or supplements. It is found in meat, fish, eggs, milk and dairy products, and in fortified foods such as some breakfast cereals, yeast extracts and soy products ⁸.

B12 is absorbed through a fairly complex process. In the stomach it combines with a protein called intrinsic factor, and the combination is absorbed further down the gut, in a part of the small intestine called the distal ileum ⁶. Problems at any step, from the stomach to the intestine, can lead to deficiency even when the diet contains enough B12.

The body stores B12 in large amounts. The NHS notes that stores can last around 2 to 5 years without being replenished, so problems can take a long time to appear after a change in diet ⁶.

Why B12 is linked to hair at all

The hair follicle is one of the most active tissues in the body. Cells in the hair bulb divide rapidly, and micronutrients take part in that cell turnover ¹. Because B12 is needed for DNA synthesis, it is reasonable to suspect that a severe shortage could affect hair. A review of vitamins and minerals in hair loss noted that only a few B vitamins, including B12, have been associated with hair loss ¹.

There is some direct evidence of hair changes in deficiency. A review of B12 in dermatology lists hair and nail changes among the skin signs of B12 deficiency, alongside darkening of the skin (the most common sign) and changes in the mouth such as glossitis, a smooth sore tongue ³. In a study of 57 infants with B12 deficiency, 13 had brittle, dull hair, and in most of them this improved within three months of B12 treatment ⁹. These findings come from people with clear deficiency, often with other signs as well. They do not show that low-normal B12 causes adult hair loss.

What studies of hair loss show

When researchers have measured B12 in adults with common types of hair loss, the results have mostly been negative.

The authors of the chronic telogen effluvium study concluded that nutritional deficiencies were not as common as thought in these patients, and that other causes should be looked for through a careful history and examination ⁵. The review of vitamins and minerals concluded that the few studies on B12 and folate in hair loss do not allow any recommendation for B12 screening or supplements for hair loss, and that the data are too limited to recommend them for alopecia areata ¹.

One older finding is worth knowing. In women with pattern hair loss treated with a combined hormonal medicine, B12 levels fell, and a daily B12 supplement corrected the levels. But the lower B12 had no effect on hair shedding or growth ¹. This is a reminder that a low number on a test is not automatically the reason for hair loss.

Premature greying is a different question from hair loss. The review notes that B12 is one of several micronutrients that may be involved in early greying, and suggests checking for deficiencies in people with premature greying ¹. For more, see Which vitamin deficiencies are linked to hair loss?.

Who is at risk of B12 deficiency

B12 deficiency is worth finding for its own sake, whatever its effect on hair. The NHS lists these main causes and risk groups ^{2 6}:

• Pernicious anaemia. An autoimmune condition in which the immune system attacks the stomach cells that make intrinsic factor, so B12 cannot be absorbed. It is the most common cause in the UK, and is more common in women around 60, people with a family history, and people with another autoimmune condition ⁶.
• Diet. People who rarely eat meat, fish or dairy products, and people on a vegan diet who do not take B12 supplements or fortified foods ⁶.
• Stomach surgery. Operations that remove part of the stomach increase risk ⁶.
• Intestinal conditions. Conditions such as Crohn's disease can reduce absorption ⁶.
• Medicines. Proton pump inhibitors (PPIs), used for acid reflux and ulcers, can reduce B12 ⁶. Metformin, a first-line diabetes medicine, is a well-known cause. A meta-analysis of 31 studies found that people with diabetes taking metformin had about twice the risk of B12 deficiency of those not taking it, and recommended yearly B12 checks for people on metformin ⁷.
• Age. B12 and folate deficiency are more common in older people, affecting around 1 in 10 people aged 75 or over ².

If none of these apply to you and you eat a mixed diet, deficiency is less likely, though not impossible.

Symptoms that point to B12, not just hair

Hair loss on its own is not a good sign of B12 deficiency. The symptoms that should prompt testing are wider ²:

• tiredness and lack of energy
• shortness of breath or a fast heartbeat
• a sore or red tongue, sometimes with mouth ulcers
• pins and needles, numbness, or problems with balance and coordination
• problems with memory, understanding or judgement
• low mood or anxiety

These symptoms usually develop gradually ². The NHS stresses that deficiency should be diagnosed and treated promptly, because some effects on the nervous system can become irreversible if left untreated ².

What testing shows

A B12 check is a blood test. A doctor may look at your haemoglobin, whether your red blood cells are larger than normal, and your B12 and folate levels ¹¹. If B12 is low, further tests may be done to find the cause, such as tests for pernicious anaemia ¹¹.

Some things to know about the results:

• Symptoms count. The NHS notes that some people have symptoms with apparently normal B12 levels, and some have low levels with no symptoms, so results should be read alongside symptoms ¹¹.
• Normal levels can hide a problem. In functional B12 deficiency, blood levels look normal but a problem with B12 transport proteins causes symptoms ⁶.
• Biotin can distort results. High-dose biotin, common in hair supplements, can interfere with some laboratory tests, including B12 tests ¹. Tell the person ordering your tests if you take biotin, and ask whether to pause it beforehand. See Biotin for hair loss: do you need it?.
• Folate and B12 go together. Folic acid can improve anaemia so much that it masks B12 deficiency, so B12 should be checked before folic acid treatment is started ⁸.

For people with hair loss, B12 is usually one of several tests chosen based on history and examination, rather than tested alone. A doctor may also check iron stores, thyroid function and other markers. See Blood tests for hair loss: what may be checked and why, Anaemia, iron and hair loss: what the link is and Ferritin and women's hair loss: what the iron number can and cannot tell you.

If your B12 is low

A low B12 needs proper treatment and, just as important, a cause. Treatment depends on why it is low ⁸:

• If the cause is diet, daily B12 tablets between meals or regular injections may be advised. People on a vegan diet may need B12 supplements for life.
• If the cause is absorption, such as pernicious anaemia, injections are usually needed long term, because tablets taken by mouth may not be absorbed well enough.
• If there are nerve symptoms, specialist care is usually needed.

The NHS notes that most people are easily treated with injections or tablets ⁸. A blood test is often done 7 to 10 days after starting treatment, and another after about 8 weeks, to check it is working ⁸.

What about the hair? If hair changes were caused by deficiency, they may improve as levels recover, as seen in infants ⁹. But many adults with hair loss and a low B12 also have another cause, such as pattern hair loss or telogen effluvium triggered by illness, stress or another deficiency. Correcting B12 is still important, but if hair loss continues, look for other causes.

If your B12 is normal

If your B12 level is normal, there is no good evidence that extra B12 will help your hair ¹. B12 has a low potential for toxicity ¹, but injections can cause skin reactions and, rarely, allergic reactions, according to a dermatology review ³. The same review notes that acne and rosacea have been reported as skin complications of B12 therapy ³.

Instead, think about the common causes of hair loss: pattern hair loss, shedding after illness or stress, thyroid problems, low iron, medicines and scalp conditions. Each has its own signs. See Hair loss in women: the common causes, explained and Thyroid problems and hair loss: signs to know.

B12 in hair supplements

Many hair supplements contain B12, often in amounts well above the daily need, along with biotin and other vitamins. For people who are not deficient, there is no evidence that the B12 in these products improves hair loss ¹. If you are at risk of deficiency, a supplement is not a substitute for a test, because a low level needs a cause, and some causes, such as pernicious anaemia, need injections. If you take a supplement with biotin, remember that it can affect blood test results ¹. For iron, a mineral where both too little and too much matter, see Iron supplements for hair loss: when they help, and when they can harm.

Life in Malaysia

Vegetarian diets are common in some Malaysian communities, for religious, cultural or personal reasons, and people who eat no meat or fish and little dairy may need fortified foods or a B12 supplement ⁶. Metformin is widely prescribed for type 2 diabetes, and if you have taken it for a long time, ask your doctor whether a B12 check is due ⁷. Many people also take acid-reducing medicines for gastric pain or reflux; mention these too. B12 tests are available through clinics and hospital laboratories. If you buy a B12 product or a hair supplement, check its status with the National Pharmaceutical Regulatory Agency (NPRA) ¹², and ask a pharmacist whether it is suitable for you; see Hair loss products at the pharmacy: what to ask the pharmacist. If you see a doctor, choose a registered practitioner; you can check registration with the Malaysian Medical Council ¹³. For an overview of treatment options, see Hair loss treatment in Malaysia: a plain guide to your options.

Bottom line

Vitamin B12 deficiency is a real and treatable condition that can cause anaemia, nerve problems and, in clear cases, hair changes. It is worth testing for if you are at risk, including if you eat few animal foods, take metformin or acid-reducing medicines, are older, or have had stomach or gut problems. But most studies of people with hair loss have not found lower B12 levels, and there is not enough evidence to recommend B12 supplements for hair loss in people who are not deficient. If your B12 is low, find out why and treat it properly. If hair loss continues, or your B12 is normal, look for the other common causes.

Frequently asked questions

Can low vitamin B12 cause hair loss?

Clear deficiency can cause hair changes, and a dermatology review lists them among its skin signs. But most studies of adults with common hair loss have not found lower B12 levels than in people without hair loss.

Should I take B12 for hair loss if my levels are normal?

There is no good evidence that extra B12 helps hair in people who are not deficient. A major review found too little data to recommend B12 supplements for hair loss.

Who should get a B12 test?

People at higher risk: those who eat few or no animal foods, older adults, people taking metformin or proton pump inhibitors, people who have had stomach surgery, and people with gut or autoimmune conditions.

What symptoms suggest B12 deficiency?

Tiredness, shortness of breath, a sore or red tongue, mouth ulcers, pins and needles, numbness, balance problems, and changes in memory or mood. Hair loss alone is not a reliable sign.

Does metformin lower B12?

Yes, it can. A meta-analysis of 31 studies found about twice the risk of B12 deficiency in people taking metformin, and suggested yearly B12 checks.

Can biotin supplements affect my B12 test?

High-dose biotin can interfere with some laboratory tests, including B12 tests. Tell the person ordering your tests if you take it.

Is low B12 linked to grey hair?

B12 deficiency has been associated with premature greying in some studies, and checking for deficiency is suggested in people who grey early.

If my B12 is low and I treat it, will my hair recover?

If the hair changes were caused by deficiency, they may improve as levels recover. Many adults also have another cause of hair loss, so if shedding continues, look for other causes.

Educational content. Not medical advice.