Clinical investigations from the RACP

Investigating patients with macrocytosis

Kylie Mason, Jeff Szer



In many patients macrocytosis is a physiological condition of no consequence, but in others it may indicate an underlying disorder or excessive alcohol consumption. Blood film examination directs further investigations.

Key Points

  • Macrocytosis may be the first clue to an underlying pathological condition (such as a haematological, hepatic or thyroid disorder or excess alcohol consumption) in some patients, while in others it may be physiological and of no consequence.
  • Macrocytosis is commonly associated with vitamin B12 and folate deficiency.
  • Patients with macrocytosis may be asymptomatic, and the finding is incidental, or they may have symptoms associated with an underlying disorder or deficiency. It is important, therefore, to thoroughly review medication and alcohol use, and consider liver or thyroid disease, gastric or ileal resection and malabsorptive syndromes.
  • Blood film examination may lead to the exclusion of factitious causes and focus further investigation, allowing appropriate therapy to be initiated.
  • Other investigations include serum vitamin B12 and folate levels, liver function tests and thyroid stimulating hormone level.