Vit B12 Def Anaemia

vit b12

Pernicious anaemia

Deficiency of vitamin B12 (B12 deficiency) could lead to anaemia. Pernicious anaemia is a condition where vitamin B12 cannot be absorbed into your body. Vitamin B12 deficiency is easily treated by regular injections of vitamin B12.

What is blood?

Human blood is made up of a fluid called plasma, which contains:

  • Red blood cells - which take oxygen around the body.
  • White blood cells - which are part of the immune system.
  • Platelets - which help the blood to clot if we cut ourselves.
  • Proteins - and other chemicals that have various functions.

Red blood cells are produced in the bone marrow, and millions are released into the bloodstream each day. A constant new supply of red blood cells is needed to replace old cells that break down. Red blood cells contain a chemical called haemoglobin, which binds to oxygen and takes oxygen from the lungs to all parts of the body. To make red blood cells and haemoglobin constantly you need a healthy bone marrow and nutrients such as iron and certain vitamins, including vitamin B12, which we get from food.

What do you understand by anaemia?

Anaemia means that:

Less red blood cells than normal, OR

Less haemoglobin than normal in each red blood cell

In either case, a reduced amount of oxygen is carried around in the bloodstream. There are various different causes of anaemia such as lack of iron or certain vitamins.

Vitamin B12 is needed to make new cells in the body such as the many new red blood cells which are made every day. Vitamin B12 is found in meat, fish, eggs, and milk - but not in fruit or vegetables. A normal balanced diet contains enough vitamin B12. A lack of vitamin B12 leads to anaemia and sometimes to other problems.

How does vitamin B12 deficiency present?

 The symptoms due to anaemia are caused by the reduced amount of oxygen in the body.

Common symptoms include: tiredness and lethargy.

Less common symptoms include: headaches, palpitations, altered taste, loss of appetite, and ringing in the ears (tinnitus).

How vitamin B12 deficiencies occur?

Pernicious anaemia (vitamin B12 deficiency)

Food containing vitamin B12 when ingested combines with a protein called intrinsic factor in the stomach. The combined vitamin B12/intrinsic factor is then absorbed into the body further down the gut at the end of the small intestine. (Intrinsic factor is made by cells in the lining of the stomach and is needed for vitamin B12 to be absorbed.)

Pernicious anemia is an autoimmune disease. The immune system protects the body bymaking antibodies against bacteria, viruses and other germs. In an autoimmune disease, the immune system makes antibodies against certain tissues of your body. If you have pernicious anaemia, antibodies are formed against your intrinsic factor, or against the cells in your stomach, which make intrinsic factor. This stops intrinsic factor from attaching to vitamin B12, and so the vitamin cannot be absorbed into your body.

Main causes include:

  • Stomach or gut problems like:
    • Surgery to remove the stomach or the end of the small intestine. This will mean absorption of vitamin B12 may not be possible.
    • Some diseases that affect the end of the small intestine where vitamin B12 is absorbed may affect the absorption of the vitamin. For example, Crohn's disease.
    • Some conditions of the stomach may affect the production of intrinsic factor, which is needed to combine with vitamin B12 to be absorbed. For example, atrophic gastritis (where the lining of the stomach is thinned).
  • Drugs, example metformin that is a drug commonly used for diabetes. Other drugs include: colchicine, neomycin, and some anticonvulsants used to treat epilepsy.
  • Dietary causes like strict vegans who take no animal or dairy produce may not eat enough vitamin B12.

How do you treat vitamin B12 deficiency?

To treat vitamin B12  deficiencyinjections would be required. Normally, about six injections are given at first, one every 2-4 days. This quickly builds up the body's store of vitamin B12. Vitamin B12 is stored in the liver. Once a store of vitamin B12 is built up, this can supply the body's needs for several months. An injection is then only usually needed every three months to top up the supply.

For pernicious anaemia the injections are needed for life. There are no side-effects from the treatment as it is simply replacing a vitamin that you need. If the cause of your lack of vitamin B12 is diet-related rather than due to pernicious anaemia then treatment may be different. That is, after the initial treatment with injections of vitamin B12, dietary supplements of vitamin B12 (cyanocobalamin tablets) may be advised instead of injections. Alternatively, injections of vitamin B12 twice a year may be recommended.


The symptoms of anaemia 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. A blood test may also be done to see that your thyroid gland is working well. (Thyroid problems are more common in people with pernicious anaemia.)


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