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Anaemia, vitamin B12 or folate deficiency - Causes of vitamin B12 or folate deficiency anaemia

NHS Choices Medical Reference

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Vitamin B12 deficiency and folate deficiency can be caused by a number of things that affect the body's ability to produce fully functioning red blood cells (cells that carry oxygen around the body).

Some of these are described below.

Vitamin B12 deficiency anaemia

Pernicious anaemia

Pernicious anaemia is the most common cause of vitamin B12 deficiency in the UK.

Pernicious anaemia is an autoimmune condition that affects your stomach. An autoimmune condition means your immune system (the body's natural defence system that protects against illness and infection) attacks your body's healthy cells.

Vitamin B12 is absorbed into your body through your stomach. A protein called intrinsic factor attaches itself to vitamin B12 so it can be absorbed from food you eat.

Pernicious anaemia causes your immune system to attack the cells in your stomach that produce the intrinsic factor. This means your body cannot absorb vitamin B12 which causes a deficiency.

The exact cause is not known, but certain things increase your risk of developing pernicious anaemia, including:

  • being 60 years of age - pernicious anaemia is most common at this age
  • being female - pernicious anaemia affects slightly more women than men
  • having a family history of the condition - nearly a third of people with pernicious anaemia also have a family member with the condition
  • having another autoimmune condition, such as Addison's disease or vitiligo - there is an association between pernicious anaemia and other autoimmune conditions


The body usually stores enough vitamin B12 to last approximately two to four years. However, it is important to have vitamin B12 in your diet to ensure  the store is kept at a healthy level.

A diet that includes meat, fish or dairy products usually provides enough vitamin B12. People who may not have enough vitamin B12 in their diet include vegans (people whose diet only contains food from plants) or those who have a very poor diet for a prolonged period of time.

Conditions affecting the stomach

Some stomach conditions or stomach operations can prevent the absorbtion of enough vitamin B12. For example, a gastrectomy (a surgical procedure where part of your stomach is removed) increases your risk of developing vitamin B12 deficiency anaemia.

Conditions affecting the intestines

Some conditions that affect your intestines (part of the digestive system) stop you from absorbing as much vitamin B12 as normal. For example, Crohn's disease (a long-term condition that causes inflammation of the lining of the digestive system) can sometimes result in your body not having enough vitamin B12.


Some types of medicine can reduce the amount of vitamin B12 in your body. For example, proton pump inhibitors (PPIs) (a medication that treats indigestion) can make a vitamin B12 deficiency worse. PPIs inhibit the production of stomach acid, needed to release vitamin B12 from food you eat.

Your GP will be aware of medicines that can affect your vitamin B12 levels, and will monitor you if they think it necessary.

Folate deficiency anaemia

Folate is a water-soluble vitamin (it dissolves in water), which means your body is unable to store it for long periods of time. Your body's store of folate is usually enough to last four months. This means you need folate in your daily diet to ensure your body has sufficient stores of the vitamin.

Like vitamin B12 deficiency anaemia, folate deficiency anaemia can develop for a number of reasons. Some are described below.


Some people do not have enough folate in their daily diet. This may be because:

  • they have recently changed their diet - for example, to lose weight
  • their diet is not healthy and balanced


Sometimes your body may be unable to absorb folate as effectively as it should. This is usually the result of an underlying condition affecting your digestive system, such as Coeliac disease.

Excessive urination

You may lose folate from your body if you urinate frequently. This can be caused by an underlying condition that affects one of your organs, such as your kidneys or liver.

The following can make you urinate frequently:

  • congestive heart failure - where the heart is unable to pump enough blood around the body
  • acute liver damage - which often occurs as a result of drinking excessive amounts of alcohol
  • long-term dialysis - where a dialysis machine filters waste products from the blood


Some types of medicine reduce the amount of folate in your body, or make the folate harder to absorb. Your GP will be aware of medicines that can affect your folate levels and will monitor you if they feel it necessary.

Other causes

Sometimes, your body requires more folate than normal. This can cause folate deficiency because you cannot meet your body's demands for the vitamin. Your body may need more folate than usual when you:

  • are pregnant
  • have cancer
  • have a blood disorder, such as sickle cell anaemia (an inherited disorder that causes your blood cells to change shape)
  • are fighting an infection or health condition that causes inflammation (redness and swelling)

Premature babies (babies born before week 37 of the pregnancy) are also more prone to developing folate deficiency anaemia because their developing bodies cannot meet the demand for the folate vitamin.


If you are pregnant or planning to get pregnant, take a daily supplement of 0.4mg of folic acid until you are 12 weeks pregnant. This will ensure both you and your baby have enough folate, and will help your baby grow and develop.

Folic acid tablets are available with a prescription from your GP or you can buy them over-the-counter from:

  • pharmacies
  • large supermarkets
  • health food stores

If you are pregnant and also have another condition that may increase your body's need for folate, such as those mentioned above, your GP will monitor you closely to prevent you from becoming anaemic.

In some cases, you may need a higher dose of folic acid. For example, if you have diabetes (a long-term condition caused by too much glucose in the blood) you should take a 5mg supplement of folic acid instead of the standard 0.4mg.

Medical Review: May 29, 2012
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