A vegan diet can increase the risk of vitamin B12 deficiency because the vitamin is found naturally mainly in animal-derived foods. Some vegetarians can also be at risk when they eat only small amounts of eggs or dairy products and do not use reliable fortified foods or supplements. However, following a vegan or vegetarian diet does not automatically mean you are deficient, and diet is not always the only cause of a low vitamin B12 result.
If you have persistent tiredness, weakness, pins and needles, numbness, balance problems, memory or concentration changes, a sore red tongue or other possible symptoms, the safest approach is to consider both your diet and other risk factors. NICE recommends using symptoms, risk factors and appropriate testing rather than assuming the cause from diet alone.
Why vitamin B12 matters
Vitamin B12 supports normal red blood cell formation and healthy nervous-system function. When levels become too low, deficiency can affect energy, blood cells, sensation, balance, thinking and other aspects of health. Symptoms can be gradual and are not specific to vitamin B12 deficiency, which means tiredness or brain fog alone cannot confirm the diagnosis.
Vitamin B12 deficiency can occur with or without anaemia. This is important because a person can have neurological or cognitive symptoms even if they have not been told they are anaemic. New or worsening nerve-related symptoms deserve timely medical assessment.
Why are vegans at higher risk of vitamin B12 deficiency?
Most natural dietary sources of vitamin B12 are animal-derived foods such as meat, fish, eggs and dairy products. The NHS therefore advises people following a vegan diet to use reliable sources such as fortified foods and, where needed, vitamin B12 supplements. Fortified breakfast cereals, some unsweetened plant drinks, yeast extract and fortified nutritional yeast are examples, but the amount varies between products, so labels matter.
The risk is not simply about whether someone identifies as vegan. NICE lists a diet that excludes or is low in animal-source foods as a risk factor particularly when fortified foods or over-the-counter vitamin B12 preparations are not used regularly. Because the body stores vitamin B12, deficiency can take time to become apparent after a dietary change.
Can vegetarians become vitamin B12 deficient?
Yes. Many vegetarians who regularly eat eggs and dairy products will obtain vitamin B12 from those foods, but intake varies. Someone who eats very little dairy or egg, follows a highly restricted vegetarian diet, or does not use fortified foods may have a lower intake. The NHS advises vegetarians to make sure they have a reliable source of vitamin B12 in their diet.
A vegetarian diet should therefore be considered as one part of the assessment rather than treated as a diagnosis. A person can eat B12-containing foods and still become deficient because of an absorption problem, medicine effect or another condition.
Does being vegan or vegetarian mean you need B12 injections?
No. Being vegan or vegetarian does not by itself show that an injection is needed. NICE says that when deficiency is suspected or confirmed to be caused by low dietary intake, people should receive advice on improving vitamin B12 intake and oral replacement should be considered. Intramuscular treatment may be appropriate in some circumstances, but the route depends on the cause, symptoms, clinical urgency, absorption and the person’s wider situation.
This distinction matters for patient safety: a diet-related risk article should not imply that injections are the automatic or preferred answer. Its role is to help readers recognise a risk, understand when testing may be sensible and know that treatment options depend on the cause.
What symptoms should vegans and vegetarians watch for?
Possible vitamin B12 deficiency symptoms include persistent or unexplained tiredness, weakness, a sore or red tongue, mouth ulcers, pins and needles, numbness, muscle weakness, balance or coordination problems, changes in vision, and changes in memory, thinking or mood. Some people have symptoms without anaemia, and some people with a low result have few obvious symptoms.
These symptoms can also be caused by many other conditions. Iron deficiency, folate deficiency, thyroid problems, diabetes, sleep problems, depression or anxiety, medicine effects and other illnesses can overlap with the same complaints. Self-diagnosing B12 deficiency from symptoms alone can therefore delay the right assessment.
When should a vegan or vegetarian consider a vitamin B12 blood test?
NICE recommends offering an initial diagnostic test when a person has at least one common symptom or sign of vitamin B12 deficiency and at least one common risk factor. A vegan diet without regular fortified foods or suitable B12 preparations is one recognised risk factor. Clinical judgement is still important, especially when symptoms are significant or there are additional risks.
Where possible, diagnostic blood samples should be taken before starting vitamin B12 replacement because tablets, injections and other B12 products can increase measured levels and make later results harder to interpret. Tell the healthcare professional if you already take a multivitamin, B12 tablet, spray, injection or other supplement.
Testing can also help identify whether diet is really the main cause. If a result is low or borderline, the clinician may consider the full blood count, symptoms, medical history and, in some situations, further tests. A low result should not automatically be blamed on a vegan or vegetarian diet.
Reliable vitamin B12 sources on vegan and vegetarian diets
For vegans, the NHS recommends a varied, balanced diet that includes fortified foods and supplements when needed for nutrients that are difficult to obtain from a vegan diet. Reliable B12 sources can include fortified breakfast cereals, fortified unsweetened plant drinks, fortified yeast extract and nutritional yeast products. Check the label because not every plant-based product is fortified and the amount of B12 can differ.
Vegetarians may obtain vitamin B12 from milk, cheese and eggs as well as fortified foods. People who eat only small amounts of these foods may still need another reliable source. If you have confirmed deficiency, do not assume that simply eating more fortified food will always be enough; the appropriate treatment depends on the cause and severity.
What happens if vitamin B12 deficiency is confirmed?
Treatment is chosen according to the cause. NICE says that for suspected or confirmed dietary vitamin B12 deficiency, advice should include how to improve dietary intake and oral vitamin B12 replacement should be considered. If someone plans to use an over-the-counter oral supplement, NICE advises choosing a product containing a recognised form such as cyanocobalamin, methylcobalamin or adenosylcobalamin.
Injections may be considered instead of oral treatment in particular clinical circumstances, for example when there is a condition that could deteriorate rapidly or where adherence to oral treatment is a significant concern. By contrast, some absorption-related causes require a very different long-term plan. This is why identifying the cause matters more than choosing tablets or injections based on diet alone.
Could a low B12 level have another cause?
Yes. NICE specifically warns that a vegetarian or vegan diet may not be the cause, or the only cause, of vitamin B12 deficiency. Other recognised causes or risk factors include autoimmune gastritis, coeliac disease, stomach or bowel surgery, some gastrointestinal conditions, older age, recreational nitrous oxide use and medicines such as metformin or proton pump inhibitors.
If your diet appears adequate but you still have a low B12 result, or if symptoms are significant, recurrent or neurological, further investigation may be needed. The same applies when the deficiency continues despite improving intake or taking supplements.
When a private B12 injection assessment may be relevant
If you already have a documented vitamin B12 deficiency, recent blood results or an established treatment plan, Biscot Pharmacy’s private vitamin B12 injection service may be able to support treatment when a pharmacist confirms that the service is clinically appropriate. Following a vegan or vegetarian diet alone does not guarantee suitability, and a pharmacist may recommend blood testing, oral replacement or GP assessment instead. A consultation does not guarantee that an injection will be given.
When to seek medical advice promptly
Arrange medical assessment if you develop persistent or worsening symptoms, particularly new numbness, pins and needles, muscle weakness, balance or walking problems, vision changes, confusion or significant memory changes. Neurological complications of vitamin B12 deficiency can sometimes become irreversible if treatment is delayed.
Seek urgent help if you are seriously unwell, collapse, have severe breathing difficulty or another medical emergency. Use NHS 111 for urgent advice when the situation is not immediately life-threatening, and call 999 for an emergency.
Conclusion
Vitamin B12 deficiency is a genuine nutritional risk for people who do not have a reliable source of the vitamin, which makes it especially important for vegans and some vegetarians to plan their intake. The key point is not to assume that diet explains every symptom or every low result. Fortified foods and supplements can help prevent dietary deficiency, testing can clarify whether deficiency is present, and treatment may involve diet, oral vitamin B12 or injections depending on the cause and clinical situation.
If you have symptoms or a previous low result, discuss them with a pharmacist, GP or another appropriate healthcare professional rather than starting repeated injections on your own.
Written by the Biscot Pharmacy Editorial Team.
Medically reviewed by Faisal Shafiq, Superintendent Pharmacist (GPhC 2067224).
Frequently Asked Questions
Are vegans more likely to develop vitamin B12 deficiency?
Vegans can be at higher risk when they do not regularly use B12-fortified foods or suitable supplements because natural dietary sources are mainly animal-derived. Risk still varies between individuals, and other causes of deficiency should not be overlooked.
Do all vegetarians need a vitamin B12 supplement?
Not necessarily. Some vegetarians get enough vitamin B12 from eggs, dairy products and fortified foods, while others have a lower intake. The important point is to have a reliable source and seek advice if your diet is restricted or symptoms suggest deficiency.
How long can it take for diet-related B12 deficiency to appear?
The body can store vitamin B12 for a long time, so deficiency may develop gradually and symptoms can appear well after a dietary change. The NHS notes that body stores can last for years without being replenished.
Should I start B12 supplements before having a blood test?
If deficiency is being investigated, diagnostic blood samples are usually taken before replacement where the clinical situation allows because supplements or injections can affect test interpretation. Tell the clinician about any B12-containing products you already use.
Are B12 injections always needed for vegans with low B12?
No. NICE says oral vitamin B12 replacement should be considered when deficiency is caused by inadequate dietary intake. Injections may be appropriate in some circumstances, but the route should be based on the cause, symptoms and clinical assessment rather than diet alone.
Which foods can provide vitamin B12 on a vegan diet?
Examples include breakfast cereals, unsweetened plant drinks, yeast extract and nutritional yeast products that are specifically fortified with vitamin B12. Check the nutrition label because not every product is fortified and the amount varies.
Disclaimer
This article provides general information and does not replace personal medical advice, diagnosis or treatment. Vitamin B12 deficiency symptoms can have other causes, and treatment depends on the cause, test results, symptoms and medical history. Do not change prescribed treatment or start repeated injections based on this article. Seek prompt medical advice for new or worsening neurological symptoms.
Clinical information sources
• NICE NG239 – Vitamin B12 deficiency in over 16s: diagnosis and management
• NHS – Vitamin B12 or folate deficiency anaemia: causes
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