In evaluating suspected macrocytic anemia, which tests are most appropriate to confirm nutritional deficiencies?

• A. Check folic acid and vitamin B12 levels
• B. Check iron studies
• C. Check erythropoietin levels
• D. Check ferritin levels

Answer: (A)

Macrocytic anemia usually results from impaired DNA synthesis caused by deficiencies of folate or vitamin B12. To confirm a nutritional deficiency as the cause, the most informative tests are serum folate and vitamin B12 levels. Iron studies or ferritin assess iron status and are more relevant to iron-deficiency anemia, which typically presents with microcytosis rather than macrocytosis, so they don’t directly confirm the nutritional deficiency behind a macrocytic pattern. Erythropoietin levels don’t identify nutrient deficiencies and aren’t used to confirm macrocytosis. If needed, you can further differentiate which deficiency is present by measuring methylmalonic acid and homocysteine, with MMA specifically rising in vitamin B12 deficiency and homocysteine rising in both, though MMA is more confirmatory for B12.