Vitamin B12 Deficiency and Hair Loss: Signs, Tests and What Helps
Last updated: August 2026
Vitamin B12 deficiency is associated with diffuse hair shedding, though it is rarely the only cause and the evidence is associative rather than proven. B12 is needed for DNA synthesis, and hair follicle matrix cells are among the fastest-dividing cells in the body, so anything that slows cell division can push follicles out of their growing phase early. The practical point is that B12 deficiency is easy to test for and straightforward to treat, and it comes with other signs worth catching: fatigue, breathlessness, a sore red tongue, pins and needles, and problems with memory or balance. Untreated, the neurological effects can become permanent, so this is one to get tested rather than self-treat.
Key Takeaways
- B12 deficiency is linked with diffuse shedding across the whole scalp, not with a receding hairline or a bald patch.
- Hair is almost never the only symptom. Fatigue, a sore tongue, pins and needles and pallor usually appear too.
- The UK adult reference intake is 1.5 micrograms a day, and reliable food sources are animal foods plus fortified foods.
- Vegans, people over 60, and anyone on metformin or long term acid reducers are the highest risk groups.
- Get tested before you supplement. Taking B12 first can normalise the blood result and hide a real deficiency.
- High dose biotin supplements can interfere with some laboratory assays, so tell your GP what you are taking.
Can vitamin B12 deficiency cause hair loss?
Low B12 is associated with telogen effluvium, the diffuse shedding pattern where hair comes out evenly from all over the scalp rather than in patches. It is a recognised nutritional contributor rather than a proven single cause, and correcting a genuine deficiency will not fix hair loss that was actually driven by something else.
The distinction that matters clinically is the pattern. Nutritional shedding is diffuse: more hair in the brush, in the shower drain and on the pillow, a thinner ponytail, but no bald patches and no receding temples. If you are seeing a widening parting at the crown or recession at the temples, that is pattern hair loss with a different mechanism entirely, and no amount of B12 will change it. Our guide to what causes telogen effluvium covers how to tell the two apart.
Why would low B12 affect hair at all?
B12, or cobalamin, is a required cofactor for DNA synthesis and for the formation of red blood cells and the myelin sheath around nerves. Hair follicle matrix cells divide faster than almost any other cell type in the body, so they are unusually sensitive to anything that constrains cell division or oxygen delivery.
Two mechanisms are usually offered, and both are plausible rather than proven:
- Impaired cell division. Without enough B12, DNA synthesis slows. In bone marrow this produces megaloblastic anaemia, with abnormally large red blood cells. The same constraint applied to a rapidly dividing follicle can shorten the growing phase.
- Reduced oxygen delivery. Anaemia means fewer functional red cells carrying oxygen. Follicles are metabolically demanding and are not a survival priority, so they are among the first tissues the body economises on.
This is the same logic that explains why iron deficiency, crash dieting, illness, surgery and severe stress all trigger shedding roughly 2 to 3 months after the event. The follicle responds to a systemic problem by stepping out of anagen, and the hair falls about three months later.
What are the symptoms of vitamin B12 deficiency?
The most common symptoms are persistent fatigue, breathlessness on mild exertion, pale or slightly yellow skin, a sore smooth red tongue, mouth ulcers, and pins and needles in the hands or feet. Symptoms develop slowly over months, which is precisely why people attribute them to age, stress or a busy period and leave them.
| Where | What you might notice | Why it happens |
|---|---|---|
| Blood and energy | Tiredness, breathlessness, palpitations, pale skin | Megaloblastic anaemia reduces oxygen carrying capacity |
| Mouth | Sore, smooth, red tongue, ulcers, altered taste | Fast-turnover mucosal cells are affected early |
| Nerves | Pins and needles, numbness, unsteadiness, weakness | B12 maintains the myelin sheath around nerves |
| Brain and mood | Poor concentration, memory lapses, irritability, low mood | Neurological involvement, covered in our B12 and memory guide |
| Hair and skin | Diffuse shedding, dull hair, pale or slightly yellow skin | Rapidly dividing follicle cells and reduced oxygen delivery |
The neurological symptoms are the ones to take seriously. Left untreated for long enough, nerve damage from B12 deficiency can become permanent, and it does not always reverse fully even after levels are corrected. On the cognitive side specifically, our article on whether B12 deficiency can cause memory loss sets out what to test and when, and our review of whether B vitamins prevent dementia looks at what the trials actually found.
Who is most at risk of low vitamin B12?
The highest risk groups are vegans and strict vegetarians who do not use fortified foods, adults over 60, people with pernicious anaemia, and anyone on long term metformin or acid-reducing medication. B12 is unusual among vitamins because it is only found reliably in animal foods, and because absorbing it depends on a working stomach and terminal ileum.
| Risk group | Why |
|---|---|
| Vegans and strict vegetarians | Plant foods contain no reliable B12. Fortified foods or a supplement are required, not optional |
| Adults over 60 | Stomach acid production falls with age, and acid is needed to release B12 from food protein |
| Pernicious anaemia | An autoimmune condition that destroys intrinsic factor, the protein required to absorb B12 |
| Long term metformin users | Metformin reduces B12 absorption in the ileum over years of use |
| Long term PPI or H2 blocker users | Less stomach acid means less B12 released from food. See our guide to long term acid reducers |
| Gastric or bowel surgery | Gastric bypass or removal of the terminal ileum removes the machinery for absorption |
| Crohn's and coeliac disease | Inflammation of the small bowel impairs absorption even with a good diet |
| Heavy alcohol use | Affects both intake and absorption, and often accompanies other deficiencies |
If you take a proton pump inhibitor such as omeprazole or lansoprazole long term, the nutrient side of that is worth understanding properly. We cover it in our piece on long term PPI use and nutrient risks, including the questions worth asking at a medication review.
How much vitamin B12 do you need, and where do you get it?
The NHS reference nutrient intake for adults in the UK is 1.5 micrograms of vitamin B12 a day, which most people who eat meat, fish, eggs or dairy meet easily. The body also stores B12 in the liver, often enough for two to five years, which is why deficiency from diet alone takes a very long time to appear and why it is so easily missed.
| Source | Notes |
|---|---|
| Liver, beef, lamb | Among the richest sources by far |
| Salmon, mackerel, sardines, tuna | Oily fish also supplies omega 3, useful for other reasons |
| Eggs and dairy | Moderate amounts, easily enough across a normal week |
| Fortified plant milks and cereals | The main practical route for vegans. Check the label, fortification is not universal |
| Nutritional yeast (fortified) | Only if the specific product states added B12 |
| Seaweed, spirulina, wheatgrass | Not reliable. These contain inactive analogues that do not work as B12 in humans |
How is vitamin B12 deficiency tested?
The first line test in the UK is serum total vitamin B12, usually ordered alongside a full blood count and serum folate. If the result is borderline or the picture is confusing, second line tests include active B12 (holotranscobalamin), methylmalonic acid and homocysteine, both of which rise when B12 is functionally low.
If you are being investigated for shedding rather than for anaemia, it is worth asking for the fuller nutritional panel in one go, because the causes overlap and a single low result rarely tells the whole story:
- Full blood count. A raised mean cell volume (MCV) suggests megaloblastic anaemia from B12 or folate deficiency.
- Serum folate. Folate and B12 deficiency look similar and often occur together, and treating folate alone while B12 is low can worsen neurological damage.
- Ferritin. Iron deficiency is a far more common cause of diffuse shedding in women than B12 is.
- Thyroid function. Both under and overactive thyroid cause shedding, and autoimmune thyroid disease often travels with pernicious anaemia.
- Intrinsic factor antibodies. Ordered when pernicious anaemia is suspected, as it changes treatment from tablets to injections.
Why you should get tested before you start supplementing
Taking a B12 supplement before your blood test can lift the serum result into the normal range while the underlying absorption problem continues. That is a genuine risk, not a technicality, because it can delay the diagnosis of pernicious anaemia, which needs injections rather than tablets and where a delay allows nerve damage to progress.
Worth flagging to your GP: biotin can distort lab results. High dose biotin supplements, common in hair, skin and nail products, are known to interfere with some laboratory immunoassays, including certain thyroid, troponin and vitamin B12 tests. This can produce falsely high or falsely low results depending on the assay.
The standard advice is to tell the person taking your blood what supplements you are on, and to stop biotin supplements a few days before testing if your clinician asks you to. This applies to our own gummies as much as to anyone else's.
What does treatment for B12 deficiency involve?
Treatment depends on the cause. Deficiency from diet alone is usually managed with oral B12 tablets and dietary changes, while deficiency from an absorption problem such as pernicious anaemia is usually treated with hydroxocobalamin injections, given as a course of loading doses and then maintenance doses at intervals. Your GP decides which route applies, based on the cause rather than on the number.
What to expect in practice: energy and mouth symptoms tend to improve within weeks, blood counts normalise over a couple of months, and neurological symptoms improve slowest and least predictably. If the deficiency was caused by something ongoing, such as pernicious anaemia or bowel surgery, treatment is usually lifelong rather than a one off course.
How long does hair take to recover after a deficiency is corrected?
Expect 3 to 6 months before you see meaningful regrowth, and up to 12 months for full density to return. Hair does not restart the moment blood levels normalise. Follicles that shifted into the resting phase have to complete it, shed, and then re-enter the growing phase, and new hair grows at roughly 1 centimetre a month.
The first sign of recovery is usually a fringe of short new hairs along the hairline and parting, not a reduction in shedding. Shedding often continues for a few weeks after the cause is fixed, which people misread as treatment failure. Take a photograph in the same light once a month rather than judging it daily.
Where do hair supplements genuinely fit?
Hair supplements are everyday nutritional support for people eating a reasonable diet, not a treatment for a diagnosed deficiency. If a blood test shows you are B12 deficient, the answer is the treatment your GP prescribes, at the dose and route they choose. A gummy is not a substitute for that, and no supplement should be sold to you as one.
Where they are reasonable is the ordinary case: you eat variably, you are not deficient on paper, and you want a consistent baseline of the nutrients that contribute to normal hair. That is a modest claim, and it is the honest one. For the biotin side of the same question, our guide to biotin for hair growth is clear about who actually benefits and who does not.
GrowPro® Hair, Skin & Nails Gummies, £22.95
Sugar free vegan gummies containing vitamin B12, biotin, zinc, MSM, bamboo silica and vitamins C, D3 and E. Zinc and biotin contribute to the maintenance of normal hair, and B12 contributes to normal red blood cell formation and reduction of tiredness.
Please note: this is a food supplement for everyday nutrition. It is not a treatment for diagnosed vitamin B12 deficiency, which needs medical management. If you suspect deficiency, get tested first, because supplementing beforehand can distort the result.
When should you see a GP?
See a GP if you have persistent unexplained fatigue, a sore or smooth red tongue, pins and needles, unsteadiness on your feet, or diffuse hair shedding lasting more than three months. Book sooner if you have any numbness, weakness or balance problems, since neurological symptoms are the ones where delay carries a real cost.
Ask specifically for a full blood count, serum B12, folate, ferritin and thyroid function. Bring a list of your medicines, including metformin and any acid reducer, and mention every supplement you take. If you are vegan or have had gastric or bowel surgery, say so at the start of the appointment, because it changes which tests are appropriate.
Frequently asked questions about B12 deficiency and hair
Will taking B12 stop my hair falling out?
Only if a B12 deficiency was genuinely contributing to the shedding. Correcting a real deficiency can allow follicles to return to normal cycling over 3 to 6 months. If your B12 is already normal, taking more will not reduce shedding, because there is no shortage for it to correct.
How long does it take to correct a B12 deficiency?
Blood levels usually respond within days to weeks of starting treatment, and blood counts normalise over roughly 8 weeks. Symptom recovery lags behind: energy and mouth symptoms improve first, nerve symptoms slowest. If the cause is ongoing, such as pernicious anaemia, treatment continues for life rather than ending.
Can you have B12 deficiency with normal blood test results?
Yes. Serum total B12 measures both active and inactive forms, so it can read normal while the usable fraction is low. If symptoms strongly suggest deficiency despite a normal result, ask about active B12 (holotranscobalamin), methylmalonic acid or homocysteine, which reflect function rather than total quantity.
Is B12 deficiency the same as anaemia?
No. Anaemia is a low red blood cell count or low haemoglobin, and B12 deficiency is one of several possible causes of it. You can have early B12 deficiency with neurological symptoms and no anaemia at all, which is exactly why relying on a full blood count alone misses cases.
Can you take too much vitamin B12?
B12 is water soluble and excess is generally excreted in urine, so toxicity is rare and no upper limit has been set in the UK. That is not a reason to take large doses casually, though, since high intakes can complicate the interpretation of blood tests and mask an absorption problem that needs diagnosing.
Do vegans always need a B12 supplement?
Effectively yes, unless they consistently eat fortified foods such as fortified plant milks, cereals or nutritional yeast. Plant foods contain no reliable active B12, and seaweed and spirulina contain analogues that do not function as B12 in humans. The Vegan Society advises a supplement or reliable fortified intake.
Which is more likely to cause my hair shedding, iron or B12?
Iron deficiency is considerably more common as a cause of diffuse shedding, particularly in menstruating women, so ferritin is usually the higher yield test. That is an argument for testing both together rather than guessing, since the symptoms overlap heavily and the two deficiencies often coexist.
Should I stop biotin supplements before a blood test?
Tell your clinician what you take and follow their advice. High dose biotin is known to interfere with some laboratory immunoassays, which can produce misleadingly high or low results for certain thyroid, cardiac and B12 tests. Many labs advise pausing biotin for a few days before testing.
Test first, then support the basics
If your hair is shedding diffusely, a blood test costs you one appointment and rules several things in or out at once. For everyday nutritional support alongside a normal diet, Watermans makes vegan, sugar free hair, skin and nails gummies in the UK, part of a range with over 5 million bottles sold since 2012.
