Your body needs vitamin B-12 to make red blood cells and keep your overall immune system healthy. Deficiency of B-12 can cause a host of diseases, most important of which are neurological impairments. The medical term for anemia caused by a deficiency of Vitamin B 12 is pernicious anemia. A deficiency of B 12  is caused when there is a failure of stomach cells to produce Intrinsic Factor (IF), which helps bind and absorb dietary B-12. Vitamin B 12 helps the body perform a whole host of functions, including production of red blood cells, absorbing folic acid and helping in the proper functioning of the nervous system.


The immune system normally makes antibodies to attack bacteria and viruses. Pernicious anaemia is caused by an autoimmune disease, which causes the immune system to make antibodies against other parts of your body. In pernicious anaemia, antibodies are formed that attack the stomach lining and damage the cells that produce intrinsic factor. This stops intrinsic factor from attaching to B12, and so the vitamin cannot be absorbed into your body.

Another cause is where the bowel cannot absorb the vitamin B12 because it has been damaged by disease (e.g. Crohn’s disease) or shortened by surgery (usually to treat bowel disease). If the bowel has been shortened by surgery, these problems can contribute to a condition known as short bowel syndrome. Short bowel syndrome is a group of problems affecting people who have had half or more of their small intestine removed. Common symptoms are diarrhoea, cramping and heartburn. Some people become malnourished because their remaining small intestine is unable to absorb enough water, vitamins, and other nutrients from food.

Occasionally, some people who follow a vegan diet may become deficient in B12. This is because B12 is not found in vegetable foods (such as fruit, vegetables and grains).


Shortage of B 12 means the body isn’t producing enough enough red blood cells, which in turn may lead to symptoms of anemia such as shortness of breath, low energy levels and fatigue. 

The classic triad of sore tongue, weakness and numbness along with pins and needles is usually present in most patients, but some may present without it. Some of the common symptoms are:

  • soreness of the tongue,
  • loss of weight,
  • pale skin, often with a lemon tint,
  • intermittent diarrhoea,
  • menstrual problems, and
  • poor resistance to infections.

If the deficiency goes on too long, the nervous system is liable to be affected, causing:

  • tingling of the fingers and toes,
  • muscle weakness,
  • staggering,
  • tenderness in the calves, and
  • confusion.


B12 deficiency is treated with a course of vitamin injections. A form of vitamin B12 known as hydroxocobalamin is injected into a muscle once every two to four days. Around six injections are given, which is enough to build up a store of vitamin B12 in the body.

The symptoms of anemia usually improve quickly once treatment has begun. You may be advised to have a blood test every year or so. This will check that the anaemia is being treated successfully.

It is common to need maintenance injections of vitamin B12 every three months for life to stop the problems coming back.

Patients whose B 12 deficiency is due to underlying problems in the stomach, gut or pancreas require additional investigations and treatment to deal with the underlying cause. Hospitalization may be indicated in severe form of anemia.

Dr. Annie

Physician, mom and wife

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