How are macrocytosis and macrocytic anaemia diagnosed?
These conditions will show up on a blood film. Your doctor may have arranged this test as part of a routine check or because you have felt unwell (see the section called Symptoms). Once the condition has been diagnosed, further tests will be arranged to find the cause. You may also need tests to check whether you have any conditions that people who have macrocytosis or macrocytic anaemia frequently develop.
The tests may include:
- A reticulocyte count. This may be raised if there is a rapid turnover of red blood cells - for example, in conditions in which red cells are destroyed, such as haemolytic anaemia. If you're found to have such a condition, more tests (for example, a Coombs' test) may be needed to investigate the cause.
- The level of folate in your blood.
- The level of serum B12 in your blood.
- Tests of your liver function.
- Checks to rule out conditions which people with some types of macrocytic anaemia develop, such as diabetes, underactive thyroid, and homocystinuria (a condition in which a chemical called homocystine and related substances build up in the blood and urine).
- If some blood disorders are suspected, you may need a bone marrow examination, but this is the exception rather than the rule.
- Other tests may be needed if your doctor suspects other conditions need to be ruled out.
What are the treatment options for macrocytosis and macrocytic anaemia?
If it has been identified that your macrocytosis is caused by a deficiency, this will need to be treated, whether or not you have anaemia.
You will also need treatment for the condition that caused the deficiency in the first place.
If you have vitamin B12 deficiency you will usually be offered an injectable form of the vitamin called hydroxocobalamin. Your doctor or practice nurse will usually inject this into a muscle
You will need the injections every other day for a couple of weeks and then every 2-3 months for life. If you have symptoms related to the nervous system, you will need injections every couple of days until your symptoms improve and then every couple of months.
B12 tablets (cyanocobalamin) are also available but do not work very well if your deficiency is due to difficulties with absorption. However, they are sometimes recommended in rare cases where the deficiency is due to lack of vitamin B12 in the diet. They can be stopped if the amount of B12 in the diet increases. A dietician may be able to help you with this.
If you have folic acid deficiency you will be advised to take folic acid tablets. 5 mg daily for four months is usually sufficient after which the dose may be reduced. If you have severe deficiency you may require folate injections for a while.
If you have vitamin B12 and folic acid deficiency it's important that the B12 deficiency is treated first; otherwise, serious spinal cord complications (subacute combined degeneration of the cord) can occur.
Treatment of the underlying cause will depend on the condition. For example, if your deficiency was due to excessive use of alcohol, this will need to be addressed.
What is the outlook for macrocytosis and macrocytic anaemia?
The outlook (prognosis) will depend on the underlying cause. In most cases of B12 or folic acid deficiency, the outlook is good once the deficiency is corrected, providing the underlying cause (for example, excessive alcohol use) can be addressed. Older people tend to have a worse outcome than young fit people. A study suggests that older people with macrocytic anaemia don't do as well as those with microcytic anaemia (in which blood cells are smaller than usual, often due to iron deficiency).
Further reading and references
Thakkar K, Billa G; Treatment of vitamin B12 deficiency-methylcobalamine? Cyancobalamine? Hydroxocobalamin?-clearing the confusion. Eur J Clin Nutr. 2015 Jan69(1):1-2. doi: 10.1038/ejcn.2014.165. Epub 2014 Aug 13.
Guidelines for the diagnosis and treatment of cobalamin and folate disorders; British Committee for Standards in Haematology (2014)
Riva E, Colombo R, Moreo G, et al; Prognostic value of degree and types of anaemia on clinical outcomes for hospitalised older patients. Arch Gerontol Geriatr. 2017 Mar - Apr69:21-30. doi: 10.1016/j.archger.2016.11.005. Epub 2016 Nov 14.
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