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Vitamin B12 or B9 (commonly called folate) deficiency anaemia occurs when a lack of vitamin B12 or folate causes the body to produce abnormally large red blood cells that can't function properly.
Red blood cells carry oxygen around the body using a substance called haemoglobin.
Anaemia is the general term for having either fewer red blood cells than normal or having an abnormally low amount of haemoglobin in each red blood cell.
There are several different types of anaemia, and each one has a different cause. For example, iron deficiency anaemia, which occurs when the body doesn't contain enough iron.
Vitamin B12 and folate perform several important functions in the body, including keeping the nervous system healthy.
A deficiency in either of these vitamins can cause a wide range of problems, including:
Some of these problems can also occur if you have a deficiency in vitamin B12 or folate, but don't have anaemia.
Read about the symptoms of vitamin B12 or folate deficiency anaemia.
See your GP if you think you may have a vitamin B12 or folate deficiency. These conditions can often be diagnosed based on your symptoms and the results of a blood test.
It's important for vitamin B12 or folate deficiency anaemia to be diagnosed and treated as soon as possible because, although many of the symptoms improve with treatment, some problems caused by the condition can be irreversible.
There are a number of problems that can lead to a vitamin B12 or folate deficiency, including:
Both vitamin B12 deficiency and folate deficiency are more common in older people, affecting around 1 in 10 people aged 75 or over, and 1 in 20 people aged 65 to 74.
Read about the causes of vitamin B12 or folate deficiency anaemia.
Most cases of vitamin B12 and folate deficiency can be easily treated with injections or tablets to replace the missing vitamins.
Vitamin B12 supplements are usually given by injection at first. Then, depending on whether your B12 deficiency is related to your diet, you'll either require B12 tablets between meals or regular injections. These treatments may be needed for the rest of your life.
Folic acid tablets are used to restore folate levels. These usually need to be taken for four months.
In some cases, improving your diet can help treat the condition and prevent it recurring. Vitamin B12 is found in meat, fish, eggs, dairy products, yeast extract (such as Marmite) and specially fortified foods. The best sources of folate include green vegetables such as broccoli, Brussels sprouts and peas.
Read about treating vitamin B12 or folate deficiency.
Although it's uncommon, vitamin B12 or folate deficiency (with or without anaemia) can lead to complications, particularly if you've been deficient in vitamin B12 or folate for some time.
Potential complications can include:
Adults with severe anaemia are also at risk of developing heart failure.
Some complications improve with appropriate treatment, but others – such as problems with the nervous system – can be permanent.
Read about the complications of vitamin B12 or folate deficiency anaemia.
Vitamin B12 or folate deficiency anaemia can cause a wide range of symptoms. These usually develop gradually but can worsen if the condition goes untreated.
Anaemia is where you have fewer red blood cells than normal or you have an abnormally low amount of a substance called haemoglobin in each red blood cell. General symptoms of anaemia may include:
If you have anaemia caused by a vitamin B12 deficiency, you may have other symptoms in addition to those listed above, such as:
Some of these symptoms can also occur in people who have a vitamin B12 deficiency, but have not developed anaemia.
Additional symptoms in people with anaemia caused by a folate deficiency can include:
See your GP if you're experiencing symptoms of vitamin B12 or folate deficiency anaemia. These conditions can often be diagnosed based on your symptoms and the results of a blood test.
Read more about diagnosing vitamin B12 or folate deficiency anaemia.
It's important for vitamin B12 or folate deficiency anaemia to be diagnosed and treated as soon as possible. Although many of the symptoms improve with treatment, some problems caused by the condition can be irreversible if left untreated. The longer the condition goes untreated, the higher the chance of permanent damage.
Vitamin B12 or folate deficiency anaemia occurs when a lack of either of these vitamins affects the body's ability to produce fully functioning red blood cells.
Red blood cells carry oxygen around the body. Most people with vitamin B12 or folate deficiency anaemia have underdeveloped red blood cells that are larger than normal. The medical term for this is "megaloblastic anaemia".
A vitamin B12 or folate deficiency can be the result of a variety of problems, some of which are described below.
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.
In your stomach, vitamin B12 is combined with a protein called intrinsic factor. This mix of vitamin B12 and intrinsic factor is then absorbed into the body in part of the gut called the distal ileum.
Pernicious anaemia causes your immune system to attack the cells in your stomach that produce the intrinsic factor, which means your body is unable to absorb vitamin B12.
The exact cause of pernicious anaemia is unknown, but the condition is more common in women around 60 years of age, people with a family history of the condition and those with another autoimmune condition, such as Addison's disease or vitiligo.
Some people can develop a vitamin B12 deficiency as a result of not getting enough vitamin B12 from their diet.
A diet that includes meat, fish and dairy products usually provides enough vitamin B12, but people who don't regularly eat these foods – such as those following a vegan diet or who have a generally very poor diet – can become deficient.
Stores of vitamin B12 in the body can last around two to four years without being replenished, so it can take a long time for any problems to develop after a dietary change.
Some stomach conditions or stomach operations can prevent the absorption of enough vitamin B12.
For example, a gastrectomy (a surgical procedure where part of your stomach is removed) increases your risk of developing a vitamin B12 deficiency.
Some conditions that affect your intestines can also stop you from absorbing the necessary amount of vitamin B12.
For example, Crohn's disease (a long-term condition that causes inflammation of the lining of the digestive system) can sometimes mean your body doesn't get enough vitamin B12.
Some types of medicine can lead to a reduction in the amount of vitamin B12 in your body.
For example, proton pump inhibitors (PPIs) – a medication sometimes used to treat indigestion – can make a vitamin B12 deficiency worse. PPIs inhibit the production of stomach acid, which is needed to release vitamin B12 from the food you eat.
Your GP will be aware of medicines that can affect your vitamin B12 levels and will monitor you if necessary.
Some people can experience problems related to a vitamin B12 deficiency, despite appearing to have normal levels of vitamin B12 in their blood.
This can occur due to a problem known as functional vitamin B12 deficiency – where there's a problem with the proteins that help transport vitamin B12 between cells. This results in neurological complications involving the spinal cord.
Folate 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.
Good sources of folate include broccoli, Brussels sprouts, asparagus, peas, chickpeas and brown rice. If you don't regularly eat these types of foods, you may develop a folate deficiency.
Folate deficiency caused by a lack of dietary folate is more common in people who have a generally unbalanced and unhealthy diet, people who regularly misuse alcohol and people following a fad diet that doesn't involve eating good sources of folate.
Sometimes your body may be unable to absorb folate as effectively as it should. This is usually due to an underlying condition affecting your digestive system, such as coeliac disease.
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:
Some types of medicine reduce the amount of folate in your body, or make the folate harder to absorb.
These include some anticonvulsants (medication used to treat epilepsy), colestyramine, sulfasalazine and methotrexate.
Your GP will be aware of medicines that can affect your folate levels and will monitor you if necessary.
Your body sometimes requires more folate than normal. This can cause folate deficiency if you can't meet your body's demands for the vitamin.
Your body may need more folate than usual if you:
Premature babies (born before the 37th week of pregnancy) are also more likely to develop a folate deficiency, because their developing bodies require higher amounts of folate than normal.
If you're pregnant or trying to get pregnant, it's recommended that you take a 400 microgram folic acid tablet every day until you're 12 weeks pregnant. This will ensure that both you and your baby have enough folate and 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 and health food stores.
If you're pregnant and 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, you should take a 5 milligrams (5mg) supplement of folic acid instead of the standard 400 micrograms.
Read more about vitamins and nutrition in pregnancy.
A diagnosis of vitamin B12 or folate deficiency anaemia can often be made by your GP based on your symptoms and the results of blood tests.
Different types of blood tests can be carried out to help identify people with a possible vitamin B12 or folate deficiency. These tests check:
However, some people can have problems with their normal levels of these vitamins or may have low levels despite having no symptoms. This is why it's important for your symptoms to be taken into account when a diagnosis is made.
A particular drawback of testing vitamin B12 levels is that the current widely-used blood test only measures the total amount of vitamin B12 in your blood.
This means it measures forms of vitamin B12 that are "active" and can be used by your body, as well as the "inactive" forms, which can't. If a significant amount of the vitamin B12 in your blood is "inactive", a blood test may show that you have normal B12 levels, even though your body can't use much of it.
There are some types of blood test that may help determine if the vitamin B12 in your blood can be used by your body, but these aren't yet widely available.
If your symptoms and blood test results suggest a vitamin B12 or folate deficiency, your GP may arrange further tests. If the cause can be identified, it will help to determine the most appropriate treatment.
For example, you may have additional blood tests to check for a condition called pernicious anaemia. This is an autoimmune condition (where your immune system produces antibodies to attack healthy cells), which means you're unable to absorb vitamin B12 from the food you eat.
Tests for pernicious anaemia aren't always conclusive, but they can often give your GP a good idea of whether you have the condition.
You may be referred to a specialist for further tests or treatment. This may include:
A dietitian can devise a personalised eating plan for you to increase the amount of vitamin B12 or folate in your diet.
Read our page on B vitamins and folic acid for information about good sources of these vitamins.
The treatment for vitamin B12 or folate deficiency anaemia depends on what's causing the condition. Most people can be easily treated with injections or tablets to replace the missing vitamins.
Vitamin B12 deficiency anaemia is usually treated with injections of vitamin B12, in a form called hydroxocobalamin.
At first, you'll have these injections every other day for two weeks, or until your symptoms have stopped improving. Your GP or nurse will give the injections.
After this initial period, your treatment will depend on whether the cause of your vitamin B12 deficiency is related to your diet. The most common cause of vitamin B12 deficiency in the UK is pernicious anaemia, which isn't related to your diet.
Read more about the causes of vitamin B12 or folate deficiency.
If your vitamin B12 deficiency is caused by a lack of the vitamin in your diet, you may be prescribed vitamin B12 tablets to take every day between meals. Alternatively, you may need to have an injection of hydroxocobalamin twice a year.
People who find it difficult to get enough vitamin B12 in their diets, such as those following a vegan diet, may need vitamin B12 tablets for life.
Although it's less common, people with vitamin B12 deficiency caused by a prolonged poor diet may be advised to stop taking the tablets once their vitamin B12 levels have returned to normal and their diet has improved.
Good sources of vitamin B12 include:
If you're a vegetarian or vegan, or are looking for alternatives to meat and dairy products, there are other foods that contain vitamin B12, such as yeast extract (including Marmite), as well as some fortified breakfast cereals and soy products.
Check the nutrition labels while food shopping to see how much vitamin B12 different foods contain.
If your vitamin B12 deficiency isn't caused by a lack of vitamin B12 in your diet, you'll usually need to have an injection of hydroxocobalamin every three months for the rest of your life.
If you've had neurological symptoms (symptoms that affect your nervous system, such as numbness or tingling in your hands and feet) caused by a vitamin B12 deficiency, you'll be referred to a haematologist, and you may need to have injections every two months. Your haematologist will advise on how long you need to keep taking the injections.
For injections of vitamin B12 given in the UK, hydroxocobalamin is preferred to an alternative called cyanocobalamin. This is because hydroxocobalamin stays in the body for longer.
If you need regular injections of vitamin B12, cyanocobalamin would need to be given once a month, whereas hydroxocobalamin can be given every three months.
Cyanocobalamin injections aren't routinely available on the NHS. However, if you need replacement tablets of vitamin B12, these will be cyanocobalamin.
To treat folate deficiency anaemia, your GP will usually prescribe daily folic acid tablets to build up your folate levels. They may also give you dietary advice so you can increase your folate intake.
Good sources of folate include:
Most people need to take folic acid tablets for about four months. However, if the underlying cause of your folate deficiency anaemia continues, you may have to take folic acid tablets for longer – possibly for life.
Before you start taking folic acid, your GP will check your vitamin B12 levels to make sure they're normal. This is because folic acid treatment can sometimes improve your symptoms so much that it masks an underlying vitamin B12 deficiency.
If a vitamin B12 deficiency isn't detected and treated, it could affect your nervous system.
To ensure your treatment is working, you may need to have further blood tests.
A blood test is often carried out around 10-14 days after starting treatment to assess whether treatment is working. This is to check your haemoglobin level and the number of the immature red blood cells (reticulocytes) in your blood.
Another blood test may also be carried out after approximately eight weeks to confirm your treatment has been successful.
If you've been taking folic acid tablets, you may be tested again once the treatment has finished (usually after four months).
Most people who have had a vitamin B12 or folate deficiency won't need further monitoring unless their symptoms return, or their treatment is ineffective. If your GP feels it's necessary, you may have to return for an annual blood test to see whether your condition has returned.
As most cases of vitamin B12 deficiency or folate deficiency can be easily and effectively treated, complications are rare.
However, complications can occasionally develop, particularly if you've been deficient in either vitamin for some time.
All types of anaemia, regardless of the cause, can lead to heart and lung complications as the heart struggles to pump oxygen to the vital organs.
Adults with severe anaemia are at risk of developing:
A lack of vitamin B12 (with or without anaemia) can cause the following complications:
A lack of vitamin B12 can cause neurological problems (issues affecting your nervous system), such as:
If neurological problems do develop, they may be irreversible.
Vitamin B12 deficiency can sometimes lead to temporary infertility (an inability to conceive). This usually improves with appropriate vitamin B12 treatment.
If you have a vitamin B12 deficiency caused by pernicious anaemia (a condition where your immune system attacks healthy cells in your stomach), your risk of developing stomach cancer is increased.
If you're pregnant, not having enough vitamin B12 can increase the risk of your baby developing a serious birth defect known as a neural tube defect. The neural tube is a narrow channel that eventually forms the brain and spinal cord.
Examples of neural tube defects include:
A lack of folate (with or without anaemia) can also cause complications, some of which are outlined below.
As with a lack of vitamin B12, a folate deficiency can also affect your fertility. However, this is only temporary and can usually be reversed with folate supplements.
Research has shown a lack of folate in your body may increase your risk of cardiovascular disease (CVD).
CVD is a general term that describes a disease of the heart or blood vessels, such as coronary heart disease (CHD).
Research has shown that folate deficiency can increase your risk of some cancers, such as colon cancer.
A lack of folate during pregnancy may increase the risk of the baby being born prematurely (before the 37th week of pregnancy) or having a low birthweight.
The risk of placental abruption may also be increased. This is a serious condition where the placenta starts to come away from the inside of the womb wall, causing tummy (abdominal) pain and bleeding from the vagina.
As with a vitamin B12 deficiency, a lack of folate can also affect an unborn baby's growth and development in the womb (uterus). This increases the risk of neural tube defects such as spina bifida developing in the unborn baby.