Nutrition and Vitamin Deficiencies · USMLE Step 1

An adult strict vegetarian presents with macrocytic anemia and hypersegmented neutrophils. Serum methylmalonic acid is normal but homocysteine is elevated. Which vitamin deficiency is most likely?

  1. Vitamin B12 (cobalamin)
  2. Vitamin B9 (folate)
  3. Vitamin B6 (pyridoxine)
  4. Vitamin C (ascorbic acid)
Show answer and explanation

Correct answer: Vitamin B9 (folate)

Folate (vitamin B9) deficiency causes megaloblastic anemia with elevated homocysteine but normal methylmalonic acid, distinguishing it from B12 deficiency.

Difficulty: Medium Question 3 of 21

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