Vitamin B12 is an essential nutrient that helps the body produce healthy red blood cells, maintain normal nerve function and make DNA. When the body does not have enough vitamin B12, a person may develop tiredness, weakness, numbness, tingling in the hands and feet, or changes in memory and concentration.
Vitamin B12 deficiency can affect people with different diets and lifestyles. It may occur when a person does not consume enough B12 or when the body cannot absorb the vitamin properly. Some people develop anaemia, while others experience nerve-related symptoms even when their blood count is not obviously abnormal.
Understanding the possible symptoms, risk factors, blood tests and treatment options can help you seek appropriate medical advice. Early diagnosis is important because untreated vitamin B12 deficiency can sometimes cause lasting neurological problems.
In This Article
- What is vitamin B12 deficiency?
- Symptoms of vitamin B12 deficiency
- Common causes and risk factors
- Foods that contain vitamin B12
- Vitamin B12 for vegetarians and vegans
- Tests used to diagnose B12 deficiency
- Treatment options
- How long does recovery take?
- Prevention and long-term care
- When to see a doctor
- Frequently asked questions
What Is Vitamin B12 Deficiency?
Vitamin B12, also called cobalamin, is a water-soluble vitamin that supports the formation of red blood cells, DNA production and the normal function of the brain and nervous system.
The body cannot make vitamin B12, so it must come from food, fortified products or supplements. The vitamin is naturally found mainly in animal-derived foods. Its absorption is a complex process involving the stomach, a protein called intrinsic factor and the small intestine.
A deficiency develops when intake is inadequate or when digestion and absorption are impaired. If it continues, vitamin B12 deficiency may cause megaloblastic anaemia, in which red blood cells become larger than normal, and can also affect nerves and other body systems.
Importantly, a person does not need to have anaemia to experience vitamin B12-related neurological symptoms. A normal-looking blood count alone may therefore not exclude the condition.
Symptoms of Vitamin B12 Deficiency
Symptoms often develop gradually and may be easy to confuse with other health problems. Their severity varies depending on how low the vitamin level is, how long the deficiency has been present and the underlying cause.
1. Persistent tiredness and weakness
Vitamin B12 deficiency can lead to anaemia, which reduces the blood’s ability to carry oxygen effectively. Some people experience persistent fatigue, low energy, weakness or difficulty managing everyday activities.
Tiredness has many possible causes, including poor sleep, iron deficiency, thyroid disorders, infection and other medical conditions. It should not automatically be attributed to low B12.
2. Numbness, tingling or pins and needles
Vitamin B12 is important for nerve function. A deficiency can cause tingling, numbness, burning sensations or reduced sensation in the hands and feet. Some people also notice weakness or difficulty sensing the position of their limbs.
These symptoms can have other causes too, including diabetes and nerve compression. Persistent or worsening symptoms need medical assessment.
3. Balance and walking problems
More significant deficiency can affect coordination, balance and walking. A person may feel unsteady or have a greater tendency to fall.
New difficulty walking, progressive weakness or worsening balance should be assessed promptly rather than managed only with supplements at home.
4. Memory and concentration difficulties
Some people with B12 deficiency report difficulty concentrating, memory changes or a feeling of mental fogginess. These symptoms are not specific to B12 deficiency and may also be related to sleep, mood, medicines or other health conditions.
If changes in thinking are persistent or affect everyday life, discuss them with a healthcare professional.
5. A sore or smooth tongue and mouth ulcers
B12 deficiency can cause glossitis, an inflammation of the tongue that may make it appear red, sore or unusually smooth. Some people also experience mouth ulcers or discomfort when eating.
6. Pale skin, breathlessness or palpitations
When deficiency causes significant anaemia, a person may experience paleness, shortness of breath during activity, headaches or a racing heartbeat. These symptoms can also result from other conditions and may need prompt investigation.
7. Mood or vision changes
Some people experience mood changes, confusion or vision problems in association with vitamin B12 deficiency. Sudden vision loss, severe confusion or other abrupt neurological symptoms should never be assumed to be caused by a vitamin deficiency; they require urgent assessment.
What Causes Vitamin B12 Deficiency?
1. Not getting enough vitamin B12 from food
People who rarely or never eat animal-derived foods may have a higher risk of low B12 intake if they do not use reliable fortified foods or supplements. This is particularly relevant to people following a vegan diet or a highly restrictive diet.
A vegetarian diet may contain some B12 through dairy products and eggs, but the amount depends on the foods consumed. These foods do not guarantee that every vegetarian will meet their individual requirements.
2. Problems absorbing vitamin B12
Even a person who eats sufficient B12 can develop a deficiency if the body cannot absorb it properly. Possible causes include:
- Autoimmune gastritis, which affects stomach cells needed for B12 absorption.
- Conditions affecting the small intestine, such as certain inflammatory or malabsorption disorders.
- Previous stomach or intestinal surgery that changes the normal absorption process.
- Other gastrointestinal conditions that interfere with vitamin absorption.
3. Medicines that may affect B12 levels
Long-term use of certain medicines, including metformin and proton pump inhibitors used to reduce stomach acid, may contribute to B12 deficiency in some people. The risk depends on factors such as duration of use and the individual’s health.
Do not stop a prescribed medicine on your own. If you take these medicines and have symptoms or risk factors, ask your clinician whether B12 testing is appropriate.
4. Increasing age
Some older adults absorb food-bound vitamin B12 less effectively because of changes in stomach function or other medical conditions. Age alone does not establish a deficiency, but it may influence whether assessment is appropriate.
5. Pregnancy and breastfeeding considerations
Vitamin B12 is important during pregnancy and breastfeeding. People who have low dietary intake, absorption problems or a known deficiency may need assessment and treatment to support their own health and the baby’s development.
If you are pregnant, breastfeeding or planning a pregnancy and are concerned about B12, discuss your diet, supplements and any symptoms with your healthcare professional.
Foods That Contain Vitamin B12
Vitamin B12 is naturally present in a range of animal-derived foods. Some packaged foods are fortified with B12, which means the vitamin has been added during production. Plant foods do not naturally provide a reliable source of B12 unless they are fortified.
| Food group | Examples | Practical advice |
|---|---|---|
| Dairy products | Milk, curd and cheese | Useful sources for people who consume dairy; amounts vary by product and portion. |
| Eggs | Cooked whole eggs | Can contribute to B12 intake for people who eat eggs. |
| Fish and seafood | Sardines, salmon and other fish | Provide B12 along with other nutrients; content varies by species and serving. |
| Meat and poultry | Chicken and other meats | Contain B12 in varying amounts. |
| Fortified foods | Selected breakfast cereals, plant-based milks and nutritional yeast | Check the label to confirm that B12 has been added and how much a serving provides. |
Some popular fermented foods and ordinary plant foods are sometimes described online as natural sources of vitamin B12. They should not be relied on as consistent sources unless the product is specifically fortified and its B12 content is documented.
Eating B12-containing foods supports nutritional adequacy, but an established deficiency caused by poor absorption may require supplements or injections even when the diet is improved.
Related reading: Best Foods for Brain Health.
Vitamin B12 for Vegetarians and Vegans
People who eat a vegetarian diet may obtain B12 from dairy products and eggs if these are part of their diet. However, intake can still be inadequate depending on the quantity and frequency consumed.
People following a vegan diet need a dependable B12 source, generally through appropriately fortified foods, a suitable supplement or both according to individual needs. Ordinary fruits, vegetables, grains, lentils and nuts do not naturally provide a reliable amount of B12.
Practical steps include:
- Check labels for vitamin B12 content in fortified foods.
- Review your usual diet rather than relying on a single food.
- Ask a doctor or registered dietitian whether supplementation is appropriate.
- Seek assessment if you have symptoms or a previously diagnosed deficiency.
If a deficiency has already developed, dietary changes alone may not be sufficient. Treatment should address both the low vitamin level and the reason it occurred.
How Is Vitamin B12 Deficiency Diagnosed?
Diagnosis usually starts with a review of symptoms, diet, medicines, medical history and risk factors. A healthcare professional may recommend blood tests to check vitamin B12 status and investigate possible anaemia or other causes of symptoms.
1. Complete blood count
A complete blood count, or CBC, measures components of the blood, including haemoglobin and red blood cells. B12 deficiency can cause enlarged red blood cells and anaemia, but a normal blood count does not completely exclude deficiency.
2. Serum vitamin B12 or active B12
A blood test measures vitamin B12, and in some settings a clinician may choose an active B12 test. Results need to be interpreted using the relevant laboratory range, symptoms and clinical history. A result close to a laboratory threshold may require further assessment.
3. Additional tests when needed
If the initial result is uncertain, the clinician may consider tests such as methylmalonic acid or other investigations. Additional blood tests may help assess folate, iron status, kidney function or other possible causes of symptoms.
4. Finding the underlying cause
If deficiency is confirmed, the clinician may investigate whether the cause is inadequate intake, a medication-related issue, autoimmune gastritis, previous surgery or another absorption problem. The cause matters because it influences the appropriate treatment and how long it may be required.
Vitamin B12 Deficiency Treatment
Treatment depends on how low the vitamin level is, the cause of the deficiency, whether the nervous system is affected and whether the person can absorb B12 normally. A clinician will recommend the appropriate formulation and duration.
1. Oral vitamin B12 supplements
Oral B12 may be suitable for some people, particularly when deficiency is related to dietary intake and there are no circumstances requiring injections. The appropriate dose and duration depend on the individual’s situation.
If you have a diagnosed deficiency, follow the recommended treatment plan rather than assuming that any ordinary multivitamin contains enough B12 to correct it.
2. Vitamin B12 injections
Injections may be preferred when deficiency is severe, absorption is impaired or neurological symptoms are present. The clinician will decide the schedule and whether ongoing injections are necessary.
3. Treating the underlying cause
Replacement therapy corrects the vitamin deficiency, but the reason for it also needs attention. For example, a person with poor dietary intake may need long-term nutritional planning, while someone with an absorption disorder may need ongoing treatment even after their blood levels improve.
4. Careful use of folic acid
Folate deficiency and B12 deficiency can produce overlapping blood abnormalities. Taking folic acid alone may improve the anaemia caused by B12 deficiency without correcting the underlying B12-related nerve problem. A clinician should assess B12 status when relevant before treating suspected folate deficiency.
Persistent numbness, tingling, weakness, balance difficulties or changes in walking need medical evaluation. These symptoms may have several causes, and timely treatment matters when B12 deficiency is responsible.
How Long Does Vitamin B12 Recovery Take?
The time needed to recover depends on the severity and duration of the deficiency, the underlying cause and the type of treatment. Some people begin to feel better within a few weeks, but it may take longer for symptoms and blood abnormalities to improve.
Nerve-related symptoms can take months to improve, and some damage may not fully reverse if the deficiency has been present for a long time. This is one reason it is important not to ignore persistent symptoms.
Your clinician may recommend follow-up appointments or blood tests to assess response. If symptoms are not improving, recur or worsen, the treatment plan and other possible diagnoses may need review.
How to Help Prevent Vitamin B12 Deficiency
Prevention depends on your diet, absorption, medical history and risk factors. A varied diet containing reliable B12 sources is useful, but some people need supplementation or medical monitoring.
- Include reliable food sources: If you consume animal products, include suitable sources such as dairy, eggs, fish or meat in a balanced diet.
- Choose verified fortified foods: If your diet excludes animal products, look for foods with declared B12 content on the label.
- Discuss supplements when appropriate: Vegan diets, malabsorption disorders and certain medical histories may make supplementation necessary.
- Review medicines with a clinician: If you take metformin or acid-reducing medication long term, discuss risk factors and testing when relevant. Do not stop prescribed medicines independently.
- Follow up after a diagnosis: Some causes need ongoing replacement or monitoring to prevent the deficiency from returning.
Vitamin B12 needs vary with age and life stage. Pregnant or breastfeeding individuals, older adults and people with chronic digestive conditions should discuss their nutritional needs with a qualified healthcare professional.
When Should You See a Doctor?
Arrange a medical appointment if you have persistent unexplained fatigue, numbness or tingling, a sore tongue, memory changes, balance problems or other symptoms that may suggest a deficiency. These symptoms are not specific to B12 deficiency, so a clinician may need to look for other causes as well.
Medical assessment is especially important if you:
- Follow a vegan or restrictive diet without a reliable B12 source.
- Have a history of stomach or intestinal surgery or a condition affecting absorption.
- Take medicines that may affect B12 status over the long term.
- Have already been diagnosed with B12 deficiency and symptoms persist.
- Are pregnant or breastfeeding and are concerned about deficiency.
Seek urgent medical assessment for rapidly worsening weakness, new problems walking, significant loss of balance or new neurological changes. Sudden one-sided weakness, facial drooping, speech difficulty, sudden vision loss or sudden severe confusion may indicate an emergency such as a stroke; do not assume these symptoms are due to low B12.
If you have persistent nerve symptoms, our guide explains when to see a neurologist.
Frequently Asked Questions
1. What are the early symptoms of vitamin B12 deficiency?
Possible symptoms include tiredness, weakness, a sore tongue, mouth ulcers, tingling or numbness and difficulty concentrating. Some people have few symptoms. Testing is needed to determine whether B12 deficiency is responsible.
2. Can vitamin B12 deficiency cause tingling in the hands and feet?
Yes. B12 deficiency can affect peripheral nerves and cause numbness, tingling or burning sensations. These symptoms can also result from other conditions, so medical assessment is important.
3. Which foods contain vitamin B12?
Natural sources include fish, meat, eggs and dairy products. Some fortified foods, including selected breakfast cereals and plant-based products, also contain B12. Check the label to confirm the amount.
4. Can vegetarians have vitamin B12 deficiency?
Yes. Vegetarians may have inadequate intake depending on how much dairy, eggs and fortified food they consume. People following a vegan diet need a dependable B12 source through fortified foods, supplements or both according to their needs.
5. Does a normal blood count rule out B12 deficiency?
No. Some people develop neurological symptoms without obvious anaemia or enlarged red blood cells. A clinician may recommend B12 testing when the symptoms and medical history suggest possible deficiency.
6. Is a vitamin B12 injection better than a tablet?
Neither option is best for everyone. Tablets may be appropriate for some people, while injections may be preferred when absorption is impaired, deficiency is severe or neurological symptoms are present. The clinician should choose the treatment based on the cause and individual needs.
7. How long does it take for B12 supplements to work?
Improvement varies by individual. Some symptoms may improve within a few weeks, while blood abnormalities and nerve-related symptoms can take longer. Follow-up may be needed to assess recovery and adjust treatment.
8. Can I take B12 supplements without a blood test?
Whether testing is needed depends on your risk factors and symptoms. If deficiency is suspected, medical assessment and testing can help identify the cause and guide treatment. Tell your healthcare professional about any supplements you already use because they may affect test results.
9. Can metformin cause vitamin B12 deficiency?
Long-term metformin use can contribute to lower B12 levels in some people. If you take metformin and have symptoms or other risk factors, discuss whether testing is appropriate. Do not stop the medicine without medical advice.
10. Can vitamin B12 deficiency cause permanent nerve damage?
Prolonged deficiency can sometimes cause nerve damage that does not fully reverse. Timely diagnosis and appropriate treatment reduce the risk of lasting complications, so persistent neurological symptoms should not be ignored.
Conclusion
Vitamin B12 is essential for healthy red blood cell formation and normal nerve function. A deficiency can cause tiredness, weakness, anaemia, tingling, memory changes and balance problems, but symptoms vary and may overlap with other conditions.
Eating reliable B12 sources or fortified foods can help prevent dietary deficiency. However, when the body cannot absorb the vitamin properly, supplements or injections may be needed. The right treatment depends on the cause, symptoms and test results.
If you suspect vitamin B12 deficiency, seek medical advice rather than relying on symptoms or self-prescribing supplements. Early assessment and appropriate treatment are particularly important when neurological symptoms are present.
Medical disclaimer: This article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Symptoms of B12 deficiency can overlap with other conditions. Consult a qualified healthcare professional for personalised assessment, testing and treatment. Seek urgent medical attention for serious or rapidly worsening neurological symptoms.
