Macrocytosis without anaemia (isolated raised MCV)

Haematology · Abnormal laboratory result · updated 2026-10-31

BioMG follows French guidelines. Adapt it to the guidelines and the tests available where you practise.

Frequency: About 3% of the general population ^[1]

MCV > 100 fL without anaemia: first-line tests

Repeat FBC with blood film examination (macro-ovalocytes, hypersegmented neutrophils)
Reticulocyte count
Vitamin B12
GGT (if alcohol consumption possible)if needednon-French guidelineAlcohol is the leading cause of macrocytosis in ambulatory care; in macrocytic patients, the screening questionnaire and GGT are the two most sensitive tests for detecting alcohol misuse ^[1].
Carbohydrate-deficient transferrin (CDT) (if alcohol consumption uncertain or disputed)if neededAlcohol consumption denied or uncertain, to discuss it with an ambivalent patient: CDT rises after at least 10 days at 60 g of alcohol a day or more, has a specificity of 80 to 90% (better than GGT) and a half-life of about 15 days; combined with GGT, its sensitivity rises to 80% ^[2].

Detailed explanation and international comparison (in French): read it in English (machine translation)

Alcohol consumption? If alcohol is the cause, see the page “Alcohol misuse: laboratory markers”.
On metformin? On metformin, macrocytosis may come from B12 deficiency: see the page “Low vitamin B12”.

TSH
AST
ALT
GGT
Serum creatinine with eGFR
Red cell folate (if no other cause is found)if needednon-French guidelineRed cell folate reflects stores better than serum folate; to be requested if no other cause is found ^[1].
Methylmalonic acid (if B12 in the indeterminate range; not reimbursed in France)if needednon-French guidelineB12 between 180 and 350 ng/L with symptoms or signs of deficiency: methylmalonic acid helps to decide ^[3]. See the page “Low vitamin B12”.

Detailed explanation and international comparison (in French): read it in English (machine translation)

Other associated cytopenia? An associated neutropenia or thrombocytopenia moves to the page “Bicytopenia or pancytopenia”.

Serum folate: it fluctuates rapidly with intake and is of little use; prefer red cell folate ^[1].

Sources (14)