Clinical QuickieHematology/Coagulation
MCV
Small, normal, or large — let it narrow the differential, not end it.
MCV Classifies; It Does Not Diagnose
First confirm there is anemia, then use red-cell size to organize the workup.
MCV is a starting point, not a conclusion.
Microcytic
Think iron deficiency, thalassemia and selected inflammatory/chronic or less common causes.
Iron studies and clinical context help distinguish between them.
Normocytic
Think CKD/inflammation, early iron deficiency, acute blood loss, hemolysis and marrow disorders.
A normal MCV can hide mixed deficiencies.
Macrocytic
Separate megaloblastic causes such as B12/folate-related impaired DNA synthesis from alcohol, liver disease, hypothyroidism, reticulocytosis and medication effects.
Not all macrocytosis is B12 or folate deficiency.
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