Vitamin B12 deficiency anaemia

Produced by Krysta Munford, Bupa Health Information Team, December 2011.

This factsheet is for people who have vitamin B12 deficiency anaemia, or who would like information about it.

Vitamin B12 deficiency anaemia is a type of anaemia that develops when there isn't enough vitamin B12 in your body. Anaemia is a condition in which your blood can’t carry enough oxygen to meet the needs of your body.

About vitamin B12 deficiency anaemia

You need vitamin B12 for many important processes inside your body, particularly for making red blood cells and keeping your nerves healthy. If you don’t have enough vitamin B12, your body won't be able to make as many red blood cells as normal. They will also be abnormally large and won't last as long as they should.

If you don't have enough red blood cells, your tissues and organs may not get enough oxygen. This leads to the symptoms of anaemia.

Symptoms of vitamin B12 deficiency anaemia

Common symptoms of all types of anaemia include:

• feeling tired
• looking pale
• increased breathlessness
  
• feeling your heart racing or thumping (called palpitations)

If you have vitamin B12 deficiency anaemia, you may also develop problems such as:

• yellowing of your skin and the whites of your eyes (known as jaundice)
• headaches
• poor appetite
• a sore mouth and tongue
• poor concentration and forgetfulness
• depression
• tingling, numbness and burning in your feet, hands, arms and legs

These symptoms may be caused by problems other than vitamin B12 deficiency anaemia. If you have any of these symptoms, see your GP for advice.

Complications of vitamin B12 deficiency anaemia

If you have anaemia, your heart has to work harder to get oxygen to your vital organs. If left untreated it can lead to problems with your heart and lungs. Vitamin B12 deficiency can also affect your movement and co-ordination, increase your risk of infertility and may be associated with a slightly increased risk of stomach cancer.

Causes of vitamin B12 deficiency anaemia

The most common cause of vitamin B12 deficiency is pernicious anaemia. This is a condition that usually develops when your body lacks a protein called intrinsic factor. Normally, intrinsic factor is released by cells in your stomach lining, where it attaches to vitamin B12. This vitamin B12-intrinsic factor complex then enters your small intestine where it is absorbed into your bloodstream. If your small intestine is unable to absorb vitamin B12, you become deficient and develop anaemia. 

Pernicious anaemia tends to run in families and is most common in people over 60. It’s an autoimmune disease, which means that antibodies produced by your immune system attack the intrinsic factor when it’s released into your stomach, or they may attack the cells in your stomach lining that produce it.

Other causes of vitamin B12 deficiency anaemia are listed below.

• Diet. Vitamin B12 is only found in meat and animal products, so if you follow a strict vegan diet, you may not get a sufficient amount for your needs.
• Surgery. You can become deficient in vitamin B12 if you’ve had surgery to remove part of your stomach.
• Bowel disease. If you have coeliac disease, for example, it can interfere with vitamin B12 absorption.
• Medicines. Certain medicines, such as neomycin, metformin and anticonvulsants, can interfere with vitamin B12 absorption.

Very rarely, children can be born with an inability to produce enough intrinsic factor, or the inability to absorb the combination of intrinsic factor and vitamin B12 in the small intestine.

Diagnosis of vitamin B12 deficiency anaemia

Your GP will ask about your symptoms and examine you. He or she may also ask about your medical history. If your GP suspects you have anaemia, you will be asked to have a blood test. Your blood will be sent to a laboratory to be tested for the following.

• A full blood count. This is to check the level of haemoglobin in your blood, how many of each of the different types of blood cell you have, the size of your red cells, and the amount of haemoglobin in each red cell.
• A blood film. This involves examining your blood under a microscope to check the size and shape of your red blood cells and to assess the different white cells that are present.
• Vitamin B12, iron and folate. The levels of each of these will be measured.

If the blood tests show that you have anaemia with enlarged red blood cells and low levels of vitamin B12, you may have vitamin B12 deficiency anaemia. You may need to have further tests to help identify the cause of your condition.

Your GP may then refer you to a haematologist (a doctor who specialises in identifying and treating conditions of the blood) or a gastroenterologist (a doctor who specialises in identifying and treating conditions that affect the digestive system).

Treatment of vitamin B12 deficiency anaemia

Your GP will try to identify why you’re deficient in vitamin B12 so that any underlying cause can be treated. Generally, if you’re not getting enough vitamin B12 in your diet, your GP will give you advice on how to adjust it, or refer you to a dietitian.

Self-help

You may be advised to take a vitamin B12 supplement (cyanocobalamin). Your GP will usually recommend you take 50 to 150 milligrams daily between meals to make up for the shortage of vitamin B12 in your diet. Always read the patient information that comes with your supplements and if you have any questions, ask your GP or pharmacist for advice.

Medicines

You may need to have a course of 1 milligram vitamin B12 injections (hydroxocobalamin). These may be a bit painful, but aren’t usually associated with any other side-effects. If you have problems with vitamin B12 absorption, such as pernicious anaemia, you will need to have injections for the rest of your life.

Hospital treatment

If you have severe vitamin B12 deficiency anaemia, you may be considered for a blood transfusion, but this is unlikely as people usually respond quickly to treatment with injections. Speak to your GP for more information.

Your GP will need to monitor you to check that your treatment is working. About seven days after you start treatment, you may be asked to have a repeat blood count to make sure that it is improving. You will then have a further blood test after about eight weeks to confirm that your haemoglobin and red blood cell levels have returned to normal.

Prevention of vitamin B12 deficiency anaemia

You only need a very small amount (1.5 micrograms) of vitamin B12 each day. If you eat a healthy, balanced diet and don't have a condition that affects your absorption of vitamin B12, you're unlikely to have a shortage and become deficient.

Good sources of vitamin B12 include meat and other animal products, such as eggs and cheese. Some breakfast cereals and bread are fortified with vitamin B12. This means that vitamin B12 has been added during manufacturing.

If you eat a vegan diet, try to include foods fortified with vitamin B12. Your GP may suggest you take regular vitamin B12 supplements to prevent anaemia.

For answers to frequently asked questions on this topic, see FAQs.

For sources and links to further information, see Resources.