Vitamin B12 Deficiency: Symptoms and Food Sources

Vitamin B12 is a nutrient your body needs to make healthy red blood cells, keep nerves working and support the brain. Because the body cannot make B12 on its own and it comes mainly from animal foods, deficiency is fairly common, particularly among vegetarians, older adults and people with certain gut conditions. The symptoms can be vague and slow to appear, so many people live with low B12 for a long time before it is recognised. Knowing the warning signs and good food sources can protect your energy and your nerves.

What does vitamin B12 do in the body?

Vitamin B12 helps form red blood cells that carry oxygen, supports the protective covering around nerves, and is needed for normal brain function and DNA production. When B12 runs low, the body makes fewer and larger red blood cells, leading to a type of anaemia, and the nerves can gradually be affected. Because these changes build up slowly, early deficiency is easy to miss.

What are the symptoms and warning signs?

Symptoms of B12 deficiency can affect the blood, nerves and mood. Watch for:

• Persistent tiredness, weakness and breathlessness on exertion.
• Pale or slightly yellow skin.
• Tingling, numbness or a pins-and-needles feeling in the hands and feet.
• A sore, smooth or red tongue and mouth ulcers.
• Poor balance, memory problems or low mood in more advanced cases.

Who is at risk of deficiency?

Some groups are much more likely to run low on B12. These include strict vegetarians and vegans, since plant foods contain almost no B12, and older adults, whose stomachs absorb it less well. Others at risk are people who have had stomach or bowel surgery, those with conditions like pernicious anaemia or coeliac disease, and long-term users of certain medicines such as metformin for diabetes or acid-reducing drugs. You can read about these medicines in our medicine directory, for example metformin, but never change a prescribed dose without your doctor.

What are good food sources of B12?

In a Bangladeshi diet, B12 comes mainly from animal foods:

• Fish, including commonly eaten local varieties.
• Eggs.
• Milk, yogurt (doi) and other dairy.
• Meat, liver and poultry.

For vegetarians, dairy and eggs are the most reliable sources, and some people may need fortified foods or a supplement. Supplements and injections are also used to treat established deficiency, but the type and dose should be decided by a doctor rather than self-prescribed.

How is B12 deficiency tested and treated?

A doctor can diagnose B12 deficiency with a simple blood test, sometimes alongside a full blood count that shows large red blood cells. If levels are low, treatment may be oral B12 tablets or B12 injections, depending on the cause and severity. People who cannot absorb B12 well from the gut often need injections. Treatment usually improves tiredness within weeks, though nerve symptoms can take longer and may not fully reverse if deficiency was severe and prolonged.

When should you see a doctor?

See a doctor if you have ongoing tiredness, unexplained tingling or numbness, a sore tongue, or memory and balance problems, especially if you are vegetarian, older, or take long-term metformin or acid-reducing medicines. Do not self-treat with high-dose supplements before testing, because the cause needs to be found. You can see a relevant specialist through our list of registered doctors, keep your prescriptions organised with our free prescription tool, and read more health tips on nutrition and anaemia.

Frequently Asked Questions

Can vegetarians get enough B12 from food?

Vegetarians who eat dairy and eggs can often get adequate B12 from milk, yogurt and eggs. Strict vegans, however, get almost none from plant foods and usually need fortified foods or a supplement. A blood test can confirm whether your level is enough.

Does metformin really cause B12 deficiency?

Long-term metformin use can reduce B12 absorption in some people with diabetes, so doctors sometimes check B12 levels periodically. Do not stop metformin on your own; instead, ask your doctor about testing and whether a supplement is needed.

How long does it take to feel better after treatment?

Energy and anaemia often improve within a few weeks of starting treatment. Nerve-related symptoms like tingling can take longer and may not fully recover if the deficiency was severe and long-standing, which is why early treatment matters.

Can I just take a high-dose B12 supplement to be safe?

It is better to test first, because tiredness and tingling have many causes, and treating blindly may delay finding the real problem. If you are at risk, your doctor can advise the right form and dose.

This article is for general health education and is not a substitute for professional medical advice; please consult a doctor about your own condition.