Check-up: vitamin B12 deficiency

When I went to my GP complaining of numbness, pins and needles, unsteadiness and memory loss he mentioned the possibility it could be a form of anemia, specifically, vitamin B12 deficiency. What is this?

We obtain vitamin B12 from foods of animal origin. It is absorbed through the small intestine and we need about 2mg per day, a small amount relative to the amount stored in the body (2-5mg). Vitamin B12 deficiency is sometimes discovered as part of routine blood-testing. The reason you are experiencing neurological symptoms is that low vitamin B12 can cause damage to peripheral nerves.

Your doctor will organise some blood tests before confirming the diagnosis. He will also want to know more about your diet, with vitamin deficiency more likely in strict vegans. Prescribed medication can also affect the proper absorption of vitamin B12, so if you are taking drugs to suppress acid production or the diabetes medication metformin, they could be the culprits.

Proper B12 absorption depends on the vitamin combining with a substance called intrinsic factor in the intestine. When intrinsic factor levels are low, vitamin B12 continues to travel down the large intestine and is excreted from the body. This type of anaemia is called pernicious anaemia and may be caused by the immune system attacking the cells in the stomach that normally produce intrinsic factor. Other causes of malabsorption include previous stomach or intestinal surgery and the abnormal growth of bacteria in the small intestine.

Older people are especially vulnerable to nerve damage from low B12 levels. It tends to affect the lower limbs more often than the arms. Walking may be impaired and prolonged, and severe deficiency can even cause delirium and dementia.

How can the deficiency be treated?

Once the cause has been identified, the replacement of vitamin B12 is relatively easy. An intramuscular injection of hydroxocobalamin, initially three times a week and then indefinitely once every three months, will mean your symptoms will gradually disappear.

It is probably wise to have a blood test done about once a year when on treatment to ensure your blood count remains normal.