Macrocytosis and Macrocytic Anaemia - Symptoms and Causes

What are the symptoms of macrocytosis and macrocytic anaemia?

You may also find relevant information in our other separate leaflets called Blood and Anaemia.

Macrocytosis does not cause any symptoms itself.

Macrocytic anaemia causes symptoms that you get with any other kind of anaemia. If it's mild you may not get any symptoms. You're more likely to notice symptoms if you are older or have coronary heart disease. Younger people can be quite anaemic without noticing any problems at all.

Symptoms you may notice include:

If you have angina, you may notice your chest pains getting worse.

If your macrocytic anaemia is due to vitamin B12 deficiency you may also notice nervous system problems such as pins and needles, numbness, vision changes and unsteadiness. You may also develop psychological problems such as depression and confusion. Normally these symptoms only develop if the deficiency is severe and it has been left untreated for a long time.

A doctor examining you may notice that you:

  • Look paler than normal (the nails and tongue are a good place to check).
  • Have a bounding pulse (a pulse which feels stronger and more powerful than normal).
  • Have signs of heart failure.
  • Have a heart murmur between the left second and third ribs when the heart is contracting (a pulmonary flow murmur).

You may notice some of these signs yourself.

What are the causes of macrocytosis and macrocytic anaemia?

Macrocytosis without anaemia can be caused by:

Depending on severity and how long the person has had the condition, some of these causes can eventually lead to anaemia.

There are two types of macrocytic anaemia:

  • Megaloblastic macrocytic anaemia
  • Non-megaloblastic macrocytic anaemia

The difference is in the presence or absence of megaloblasts. These are large, abnormally developed red blood cells visible when a pathologist uses a microscope to look at a slide smeared with blood.

Causes of macrocytic megaloblastic anaemia include:

  • Serum B12 deficiency (when associated with a low haemoglobin, this is called pernicious anaemia).
  • Surgery that removes a part of the stomach (gastrectomy) or part of the gut called the ileum (ileal resection) causing difficulty in absorbing vitamin B12 from the diet.
  • Infection of the gut with germs (bacteria) or parasites (organisms that live in the body and obtain nutrition from it).
  • HIV infection.
  • Deficiency of vitamin B12 in the diet - this can happen in strict vegans but even then it is rare.
  • Folic acid deficiency. This can be due to:
    • Not eating enough foods containing folic acid. Foods high in folic acid include broccoli, Brussels sprouts, asparagus, peas, chickpeas and brown rice.
    • Conditions affecting the gut - for example, coeliac disease.
    • Inflammatory conditions such as Crohn's disease.
    • Some blood disorders can lead to a very high turnover of red blood cells - for example, sickle cell disease and thalassaemia. Normal amounts of folic acid in the diet may then not be enough and supplements may need to be taken.
    • Some medicines interfere with folic acid. Therefore, you may need to take extra folic acid whilst taking certain medicines. These include colestyramine, sulfasalazine, methotrexate and some anticonvulsant medicines used to treat epilepsy. If you need dialysis then you may be recommended to take folic acid supplements.

Causes of macrocytic non-megaloblastic anaemia include:

  • Alcohol dependency.
  • Liver disease.
  • Severe underactivity of the thyroid gland (hypothyroidism).
  • An increase in the number of immature red blood cells called reticulocytes (reticulocytosis).
  • Other blood disorders including myeloid leukaemia, aplastic anaemia (a condition affecting the bone marrow) and some other rare blood conditions.
  • Medicines that affect how the genetic material DNA is produced, such as azathioprine.

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Dr Laurence Knott
Peer Reviewer:
Dr John Cox
Document ID:
29444 (v1)
Last Checked:
09 July 2017
Next Review:
08 July 2020

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.