Macrocytosis and Macrocytic Anaemia

Macrocytosis means that the blood cells are larger than normal. When the macrocytosis is combined with a lower than normal haemoglobin, this is known as macrocytic anaemia.

What are the symptoms?

Macrocytes are the big guys of the blood cell world. Providing they have enough sense to carry around an amount of haemoglobin (the protein that makes sure oxygen gets to all your relevant bits) appropriate to their, size they won't in themselves cause you any problems.

Problems arise when each macrocyte contains less haemoglobin than it should, Then you are into symptoms of anaemia. It's a bit like the love child of that Monday morning feeling and the worst hangover you've ever had. You'll feel tired, get puffed out when you try to exercise, and your heart may start thumping. A doctor checking you out may notice you look pale, have an unnaturally strong pulse and a heart murmur.

Read more about the symptoms of macrocytosis and macrocytic anaemia.

What are the causes?

This is where it gets complicated. You can have macrocytosis with or without anaemia. Macrocytosis with anaemia can be divided up again depending on whether a pathologist looking down a microscope can or cannot see megaloblasts on a blood film. Megaloblasts are eternal teenagers, forever wanting to mature into fully formed red blood cells but unable to do so.

Macrocytosis without anaemia, macrocytic megaloblastic anaemia and macrocytic non-megaloblastic anaemia all have different causes, although the causes can overlap. Lack of vitamin B12 or folic acid is often involved somewhere along the line although liver disease, alcohol excess and medication can also be implicated.

Is that all clear? Good. Now perhaps you can explain it to me.

Learn more about the causes of macrocytosis and macrocytic anaemia.

How is the diagnosis made?

People have blood tests for all different reasons and sometimes macrocytosis with or without anaemia shows up on a blood film quite by chance.

Needless to say, if it does show up you're then in for lots of other blood tests, but most of them can be done through one needle.

You might need to have a bone marrow sample taken but the odds of that are pretty slim. You stand more chance of hearing a politician answer the question that's been put to them.

Find out more about how macrocytosis and macrocytic anaemia are diagnosed.

What treatment options are available?

If you've been found to have a deficiency, this will need to be treated. If it's vitamin B12, you'll probably end up having injections. If you don't like needles, it's tough but you need to realise that if the deficiency is left untreated you can develop all sorts of complications. The injections will be every other day to start with but eventually every few months, so it won't be so bad. Tablets are available but if your deficiency is due to difficulty in absorbing B12 through the stomach you might as well chew on a Smartie®.

Folic acid deficiency will also need treating but this time you can have tablets.

Whatever caused the deficiency in the first place will also need treating. If it was booze, you need to lay off the booze. Easier said than done, but help is available from your doctor and a variety of local services accessible in the community.

Read more about the treatment of macrocytosis and macrocytic anaemia.

What is the outlook?

Outlook (prognosis) depends on the cause but is better in younger, otherwise fit, people.

Learn more about the outlook for macrocytosis and macrocytic anaemia.

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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.