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HealthInfo Waitaha Canterbury

Vitamin B12 deficiency & pernicious anaemia

Te mimititanga huaora B12 me te mate waihanga pūtau toto whero

Selection of foods containing vitamin B12Being low in vitamin B12 can cause serious problems as it's needed to make red blood cells that carry oxygen around your body. It also helps your nerves and brain.

Most people get vitamin B12 from animal foods such as eggs, dairy, meat and seafood. It isn't found in fruit and vegetables. You also need a protein called intrinsic factor in your stomach to be able to get the vitamin B12 into your blood.

People at risk of vitamin B12 deficiency include:

Causes of vitamin B12 deficiency

The commonest cause of vitamin B12 deficiency is a condition called pernicious anaemia. It's an autoimmune condition that causes antibodies from your own immune system to attack the cells in your stomach that make a protein called intrinsic factor. This means your body can’t absorb vitamin B12. We do not know why this happens.

Pernicious anaemia usually develops in people aged over 50. Women are more often affected than men and it tends to run in families. It occurs more often in people who have other autoimmune diseases.

Other things that can cause low vitamin B12 include:

Symptoms of vitamin B12 deficiency

If you have low red blood cells such as in pernicious anaemia, you might:

Severe or long-lasting pernicious anaemia can damage your heart, brain and other organs. It can also cause other problems, such as nerve damage, memory loss and gut problems. You may also have a higher risk for weakened bone strength and stomach cancer.

See your general practice team if you have the symptoms listed above.

Treating vitamin B12 deficiency

You can help yourself by choosing good food sources of vitamin B12, such as:

If you have mild vitamin B12 deficiency, you may be able to increase your levels by taking vitamin B12 or vitamin B complex supplements. These aren't free on prescription, but you can buy them from some pharmacies and supermarkets. You'll need at least 50 mcg (micrograms) of Vitamin B12 a day.

If you have more serious vitamin B12 deficiency, you'll need vitamin B12 injections to replace, then keep up your body stores of vitamin B12. If you have pernicious anaemia, you'll need these injections every two to three months for the rest of your life.

  HealthInfo recommends the following pages

On the next page: Eating well to prevent vitamin B12 deficiency

Written by HealthInfo clinical advisers. Last reviewed February 2023.


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