Macrocytosis (isolated)

Who to refer:

• Macrocytosis with increased reticulocyte count
• For patients with macrocytosis with any additional full blood count abnormality – e.g. anaemia, neutropenia, thrombocytopenia, monocytosis, or combinations of abnormalities – please follow the separate macrocytic anaemia guidance.

Who not to refer:

Simple macrocytosis, where all the above investigations are normal, (or the macrocytosis persists despite adequate replacement/treatment), and there are no additional blood count abnormalities. In this case, the patient has idiopathic macrocytosis and should be reassured that no further tests are needed.

 In such cases, it is reasonable to re-check a FBC if the patient develops additional symptoms, or if there is suspicion of additional haematological abnormalities.  However, there is no need for regular FBC review.

How to refer:

SCI Gateway – please refer to the Department of Haematology BGH. However please see further detail in notes above.

Primary care investigations

• B12 and folate.  Treat if deficiency is detected.
• Blood film
• Reticulocyte count. 
• Thyroid function tests.  Treat if abnormality is detected.
• Liver function – excess alcohol and chronic liver disease commonly cause macrocytosis, sometimes with associated thrombocytopenia