There are 62 million diabetics in India. Many of these patients are prescribed metformin as it can safely combine with a variety of other medications and has relatively few side effects too. In recent times, however, the long-term (more than four months) use of metformin has been associated with a fall in the body's vitamin B12 levels.

The body does not synthesise B12 or store it adequately. The vitamin has to be obtained from food and absorption requires binding with a chemical called "intrinsic factor" that is secreted by cells lining the stomach.

Non-vegetarian food (meat, fish and eggs) contains vitamin B12. Vegetarian food (except dairy) contains negligible amounts. In many countries, cereals and other vegetarian food are fortified with B12, but even then vegetarians can gradually become deficient in it.

As age increases, the number of stomach cells secreting intrinsic factor decrease. Also, the stomach becomes atrophic and absorption becomes less efficient. People who take proton pump inhibitors, such as omeprazole and pantoprazole, also tend to develop atrophic gastritis. This can result in vitamin B12 levels dropping. Older people are also more likely to eat a diet inadequate in nutrients.

Others at risk of deficiency are those who have had bariatric surgery or removal of a part of the intestine. People with IBS (inflammatory bowel syndrome), parasitic infestation, thyroid problems and autoimmune diseases are also at risk.

Vitamin B12 is essential for the formation of red blood cells in our body. Low levels of it cause a type of anaemia in which the red blood cells are larger than normal. This is called megaloblastic anaemia and can also occur with folic acid deficiency. The symptoms are pallor, listlessness, tiredness and difficulty in performing daily tasks. In older people, this can be confused with depression.

Efficient nerve function also requires vitamin B12. Deficiency can cause peripheral neuritis, with tingling numbness, loss of balance and a sensation of falling. As sensation to the feet is affected, the gait may become broad-based with loss of balance. Later, the brain may become affected. There may be forgetfulness and cognitive decline, symptoms mistaken for dementia and delirium.

These symptoms can occur with a variety of medical conditions like diabetes, thyroid problems, anaemia from other causes and other vitamin deficiencies. Since they can also be a normal part of ageing, the correct diagnosis is often missed.

It is possible to determine vitamin B12 levels with a blood test. Normal levels are 50 and 400 ng/L.

Children can be deficient in B12 if they were born to mothers deficient in it, have a parasitic infestation or are strict vegetarians with an inadequate dairy intake. The symptoms are non-specific: lethargy, weakness, memory loss and hyperpigmentation of the skin.

Injections of B12 bring the levels rapidly back to normal. They are required if there is atrophic gastritis or stomach surgery. Otherwise, oral supplementation works more slowly but is almost as efficient. Extra vitamin B12, if ingested, is excreted in the urine. No harmful effects are documented.

As you grow older, check with your doctor if you need any mineral and vitamin supplements, especially of the sunshine vitamin D, B12 and calcium.

Daily Dose

• Infants up to 6 months: 0.4 microgramme 
• Babies between 7 and 12 months: 0.5 mcg
• Children between 1 and 3 years: 0.9 mcg
• Kids from 4 to 8 years: 1.2 mcg
• Children from 9 to 13 years: 1.8 mcg
• Teens up to 18: 2.4 mcg
• Adults: 2.4 mcg (2.6 mcg per day if pregnant and 2.8 mcg per day if breastfeeding)

The writer is a paediatrician with a family practice at Vellore and author of Staying Healthy in Modern India. If you have any questions on health issues please write to yourhealthgm@yahoo.co.in