What vitamin B12 does
Vitamin B12 is needed to make healthy red blood cells, keep nerves working and make DNA, the genetic material in every cell. The body cannot make it, so it must come from food. It is found naturally mainly in animal foods such as milk, curd, paneer, eggs, fish, chicken and meat.
The body stores B12 in the liver, so a deficiency usually develops slowly over months or years. When levels finally fall, it can cause anaemia, nerve damage and changes in memory and mood. Nerve damage that goes on for a long time may not fully recover, which is why early detection matters.
Who is at risk?
In India, many people follow a vegetarian diet with little milk or curd, and pure vegan diets contain almost no natural B12. Absorption of B12 also needs stomach acid and a protein called intrinsic factor, so problems in the stomach or gut can lead to deficiency even when the diet is good.
People with more than one risk factor, such as an older vegetarian who takes metformin, are at particularly high risk. Heavy alcohol use and some gut infections can also reduce absorption. If you belong to any of these groups and have symptoms, ask your doctor whether a B12 test is needed.
- Vegetarians and vegans, especially those who take little dairy
- Older adults, who absorb B12 less well
- People taking metformin for diabetes for a long time
- Long-term use of acidity medicines such as pantoprazole or omeprazole
- Pernicious anaemia, an autoimmune condition affecting absorption
- Past stomach or bowel surgery, or conditions like coeliac disease
- Babies breastfed by mothers who are low in B12
Symptoms of vitamin B12 deficiency
Symptoms start slowly and can be mistaken for stress or ageing. Common ones include tiredness, weakness, breathlessness, pale or slightly yellowish skin, a sore, red tongue and mouth ulcers. Some people have loss of appetite or weight loss. Heart palpitations may occur when anaemia is marked.
Nerve symptoms include tingling, pins-and-needles or numbness in the hands and feet, unsteady walking, and problems with balance, especially in the dark. There can also be forgetfulness, confusion, irritability and low mood. Some people have nerve symptoms even without anaemia. In babies, low B12 can cause poor feeding, weakness and delayed development. Because these signs overlap with many other conditions, a blood test is the only way to be sure.
Tests and diagnosis
A complete blood count may show anaemia with large red blood cells. A serum vitamin B12 test measures the level in the blood. Because B12 results can sometimes be borderline, your doctor may also order homocysteine or methylmalonic acid, which rise when the body is short of B12.
If the cause is not clear, especially if you eat enough B12-rich foods, tests for pernicious anaemia, such as intrinsic factor antibodies, may be done. Your doctor will also check folate, iron and thyroid levels, since these problems often occur together and can have similar symptoms.
How vitamin B12 deficiency is treated
B12 deficiency is treated with vitamin B12 as tablets, sublingual forms, or injections. Injections are often used when symptoms are severe, when there are nerve problems, or when the body cannot absorb B12 from the gut, as in pernicious anaemia. Some people need injections for life. Your doctor will decide the form, strength and length of treatment.
Energy usually improves within weeks, but nerve symptoms may take months to get better, and very long-standing damage may not fully go away. Do not stop treatment on your own once you feel better, especially if the cause is poor absorption. Follow-up blood tests show whether the treatment is working.
Food and prevention
Include B12 sources in your daily diet. For vegetarians, milk, curd, buttermilk and paneer are the main sources; eggs are a good option for those who eat them. Some foods are fortified with B12, such as certain breakfast cereals and plant milks. Vegans usually need a B12 supplement as advised by a doctor or pharmacist.
If you take metformin or acidity medicines long term, ask your doctor whether you need periodic B12 checks. Do not stop these medicines on your own because of B12 concerns. Pregnant and breastfeeding women who are vegetarian should discuss B12 with their doctor to protect the baby's development.
Cooking does not destroy much B12, but boiling milk for very long periods and reheating it again and again may reduce it slightly. More important is taking dairy or eggs regularly across the day. For any doubt about your diet, symptoms or supplements, talk to your doctor or pharmacist.
Medicines doctors commonly use
Only your doctor can decide which medicine, dose and combination is right for you.
- Vitamin B12 tablets (methylcobalamin or cyanocobalamin)Replace B12 when the gut can still absorb it, or to maintain levels after injections.Follow your doctor's or pharmacist's advice on strength and duration.
- Vitamin B12 injections (cyanocobalamin or hydroxocobalamin)Quickly raise B12 levels, especially with nerve symptoms or poor absorption.Given only on a doctor's prescription; some people need them lifelong.
- Folic acidTreats folate deficiency that may occur along with low B12.Should not be given alone when B12 is low, as it can hide anaemia while nerve damage continues.
See a doctor urgently if
- Numbness, weakness or unsteadiness that is getting worse quickly
- Confusion, memory loss or marked changes in behaviour
- Severe breathlessness, chest pain or fainting
- Vision problems along with tingling or weakness
- Poor feeding, floppiness or delayed milestones in a baby
Tests that may help
This article is general health information, not medical advice. Do not start, stop or combine medicines on your own — always follow your doctor's prescription and ask your pharmacist if unsure.