Expert reviewer Dr Prem Mahendra, Consultant Haematologist
Next review due June 2021

Anaemia is a condition in which you don’t have enough red blood cells or haemoglobin to meet your body’s needs. Your red blood cells use haemoglobin to carry oxygen around your body in your blood.

If you have anaemia, the tissues and organs around your body may not be able to get enough oxygen. This can leave you feeling tired, weak and short of breath. There are many reasons why you may develop anaemia. It can be down to something as simple as your diet, or it can sometimes be a sign of an underlying condition. Identifying the problem means you can get the treatment you need.

A woman chopping up a salad

Causes of anaemia

There are lots of reasons why you may develop anaemia, but it generally develops as a result of one of the three basic mechanisms below.

  • Your body isn’t making enough healthy red blood cells. This could be due to not getting enough iron, vitamin B12 or folate in your diet for example, or by problems with absorbing these nutrients. If you have an underlying problem with your bone marrow, this also means you won’t produce enough blood cells.
  • Your red blood cells are broken down too quickly by your body (haemolytic anaemia) .
  • You’ve had significant blood loss. This might be sudden blood loss due to a trauma, or it could be gradual blood loss over a long time. This might be due to heavy periods in women or conditions that cause bleeding in your intestines such as piles or peptic ulcers.

Nutrient deficiency

Not having enough of certain vitamins or minerals (being deficient) can mean your body is unable to make enough red blood cells. The most common type of anaemia is iron-deficiency anaemia. You can also become anaemic if you don’t have enough vitamin B12 or folate. You can become deficient for a number of reasons.

  • Pregnancy – if you’re pregnant, you’ll need more iron and folate than normal. The amount you normally get from your diet may no longer be enough.
  • Lacking these nutrients in your diet. If your diet is poor, or you follow a very strict vegan diet, you’re at greater risk.
  • Having a condition that affects the absorption of these nutrients from your intestine – like Crohn’s disease, coeliac disease or pernicious anaemia.

Other causes of anaemia

Here are some of the less common reasons why you may become anaemic.

  • Having a condition that affects your bone marrow, such as leukaemia or aplastic anaemia. Your bone marrow is the part inside your bones where your blood cells are made, so these conditions can mean you don’t make as many.
  • Certain conditions, including infections, cancers, and diseases that affect your immune system, can cause ongoing inflammation in your body. This can lead to fewer red blood cells being produced.
  • Autoimmune conditions such as rheumatoid arthritis or infections such as glandular fever can cause your body to destroy the red blood cells.
  • Genetic disorders, such as thalassaemia and sickle cell anaemia cause red blood cells to be destroyed, or misshapen so they don’t work properly.
  • Chemotherapy for cancer treatment can affect your bone marrow, which may result in anaemia.
  • Chronic kidney disease can affect the production of your red blood cells, leading to anaemia.

Symptoms of anaemia

If you have anaemia that’s developed slowly over time, you may not have any symptoms at all. You may eventually start to notice some symptoms though. These may include the following.

You may:

  • look pale
  • feel tired and weak
  • not feel able to do as much exercise as you normally would
  • feel dizzy
  • feel short of breath after exercise
  • have a thumping or unusual beating of your heart (palpitations)

You may have certain other symptoms too, depending on what’s causing your anaemia. For instance, your faeces may be dark and tarry-looking if you have a condition causing bleeding in your intestines. You may have a sore tongue or changes in your taste if you’re deficient in iron, folate or vitamin B12.

These symptoms can also be caused by other things, but if you do have any of the above, contact your GP surgery for advice.

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Diagnosis of anaemia

Your GP will ask about your symptoms and examine you. They may ask you questions about your diet and any medication you’re taking, as well as any recent illnesses you’ve had and your family history. If your GP suspects you have anaemia, they’ll ask you to have a blood test. The blood test will check for different things. These include the level of haemoglobin in your blood, how many blood cells you have, and the size and shape of your red blood cells. Your doctor may also check your iron, vitamin B12, and folate levels.

A blood test may be all you need if it’s obvious what’s causing your anaemia (for instance, you’ve developed anaemia while you’re pregnant). If there isn’t an obvious cause, you may need to have further tests and scans. Some of these investigations may need to be done at the hospital.

Depending on the results of your tests, your GP may refer you to a specialist for further investigation and treatment. This may include a haematologist (a doctor that specialises in blood disorders).

Treatment of anaemia

How your anaemia is treated will depend on what’s causing it. Your doctor’s main concern will be to identify any underlying condition that may be causing your anaemia, and to treat this if necessary. You may need to stop taking certain medications if these are the cause of your anaemia.

Sometimes your doctor may just need to keep an eye on you if your anaemia isn’t causing you too many problems. But if it’s starting to have a significant impact on your quality of life, you may need treatment.

Outlined below are some of the main treatments for various types of anaemia.

Nutritional supplements and diet

If you’re found to be deficient in iron, folate or vitamin B12, taking supplements of these nutrients can boost the levels in your body. Your GP may be able to prescribe these for you. Iron and folate are usually taken as tablets by mouth, while you may have vitamin B12 as injections or tablets. You may need to continue taking supplements for several months until the levels in your blood are back to normal. Sometimes, you may need to carry on taking them over the long term (for more information, see FAQ: How long will I need to take vitamin B12 supplements for?). Side-effects like constipation, diarrhoea, nausea and sickness are common with iron tablets. Talk to your pharmacist if you have any problems with your tablets – you may be able to try a different type.

Your GP may also give you some advice on how to get more iron, vitamin B12 or folate in your diet. This will help to maintain your levels of these nutrients in the long run and stop you from getting anaemic again. Below lists some good sources of iron, folate and vitamin B12.


  • Red meats including beef and lamb.
  • Dark green vegetables including spinach, watercress and kale.
  • Dried fruits such as apricots, prunes and raisins.
  • Iron-fortified bread.


  • Poultry, pork and shellfish.
  • Chickpeas and peas.
  • Brown rice.
  • Green vegetables including spinach, kale and broccoli.
  • Fortified foods, such as cereals.

Vitamin B12

  • Red meats including beef and lamb.
  • Eggs.
  • Milk and other dairy products.
  • Fortified soy, bread and cereal products.
  • Salmon and cod.

Treatments for severe and ongoing anaemia

You may be offered one or more of the following treatments if you have severe anaemia or it’s not something that can be treated with nutritional supplements.

  • Erythropoietin stimulating agents (ESAs). This is a type of treatment that can help your bone marrow to make more red blood cells. It might be an option if you have anaemia associated with a chronic disease, such as an infection, kidney disease or heart failure.
  • Blood transfusion. A blood transfusion involves being given blood from a carefully selected donor, into one of your veins, via a drip in your arm. You might need to stay in hospital for a blood transfusion. It’s used in all types of anaemia, although usually only as a last resort if you have particularly severe symptoms.
  • Corticosteroids or surgery to remove your spleen (splenectomy). Your doctor may suggest these treatments if your anaemia is caused by an autoimmune condition.
  • Immunosuppressive therapy. You may be offered this if you have a severe type of anaemia in which your bone marrow isn’t producing enough blood cells (aplastic anaemia).
  • Stem cell transplant. This is a procedure sometimes recommended for people with aplastic anaemia. It involves replacing your bone marrow that isn’t working properly with stem cells from a donor. These cells can produce new, healthy bone marrow.

Less common types of anaemia, such as sickle cell anaemia, have specific treatments and will be managed differently to other types of anaemia.

Complications of anaemia

You may develop complications if your anaemia is severe and you haven’t received adequate treatment. Complications can vary depending on the type of anaemia you have. Some general complications of anaemia may include the following.

  • Heart problems – anaemia can make any existing heart problems you have, such as angina or heart failure, worse.
  • Increased risk of infections, due to an effect on your immune system.
  • Increased risk of your baby being born prematurely, or with a small birth weight, if you have iron-deficiency anaemia when you’re pregnant. This can be prevented by taking any iron supplements you’re prescribed during pregnancy.

There can also be complications associated with some of the treatments you may have for your anaemia, such as blood transfusions, erythropoietin stimulating agents, immunosuppressive therapy and stem cell therapy.

Prevention of anaemia

Many types of anaemia can’t be prevented. But following a healthy, well balanced diet will help to make sure you’re getting enough iron, folate and vitamin B12. This can help to prevent some types of anaemia. See our Treatment section to find out about good sources of these foods. Talk to your GP or pharmacist if you follow a vegan diet, as it could be worth taking supplements of certain vitamins that you may be missing.

If you’re at particular risk of developing iron-deficiency anaemia, your GP may suggest you take regular iron tablets to prevent anaemia. This might be if you have heavy periods, you’ve had recurring anaemia, or you have a condition that affects absorption of iron from your intestine.

Frequently asked questions

  • You may be prescribed vitamin B12 injections or tablets if you have anaemia caused by low vitamin B12 levels. How long you’ll need to take them for depends on what’s causing your vitamin B12 deficiency and how well controlled your vitamin B12 levels are.

    More information

    If your vitamin B12 levels are low due to your diet, you may just need to take supplements until they get back to normal. You may be offered injections or tablets, which you’ll need to take for a couple of months at least. When the levels of vitamin B12 in your body get back to normal, you may be able to stop taking the supplements. You’ll need to make sure you’ve made changes to your diet first though, to stop the anaemia coming back.

    Many people will find that they need life-long treatment with vitamin B12 injections to stop their anaemia from coming back. This may be more likely if:

    • you’re vegan or vegetarian
    • your vitamin B12 deficiency is caused by something other than your diet

    If you’re vegan or vegetarian, it’s unlikely that you’ll be able to maintain the levels of vitamin B12 in your body through your diet alone. This is because the most common sources of vitamin B12 come from animal products like meat, eggs and dairy products. You’ll probably be advised to continue taking tablets or injections for life. If you have vitamin B12 deficiency anaemia that’s caused by an underlying condition such as pernicious anaemia, your body can’t take in (absorb) vitamin B12 from the foods you eat. You’ll need to take vitamin B12 injections for life.

    If you’re having difficulties with vitamin B12 tablets or injections, talk to your doctor for advice.

  • This depends on what’s causing the anaemia. How quickly it’s developed can also make a difference to how much it affects you.

    Vitamin deficiency anaemias are usually easily treated with supplements and by making small changes to your diet. Not getting adequate treatment for your anaemia can lead to potentially serious complications though, such as heart problems and complications in pregnancy.

    Other types of anaemia can be more serious. For instance, aplastic anaemia is a much more serious condition in which you don’t produce enough of any blood cells. In the past, people wouldn’t have been able to survive this types of anaemia. But treatments available these days mean the outlook for most people is much better. There can also be a serious medical condition causing the anaemia, such as leukaemia or cancer that has spread to the bone marrow.

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Related information

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    • Anemia. Medscape., updated 9 November 2017
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    • What are donor stem cell (allogenic) transplants? Macmillan Cancer Support., reviewed 28 February 2017
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  • Reviewed by Pippa Coulter, Freelance Health Editor, June 2018
    Expert reviewer Dr Prem Mahendra, Consultant Haematologist
    Next review due June 2021

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