<prompt> A man presents with fatigue. Hemogram analysis done suggested low Hb, high MCV. The next investigation is?Vit B12folatelevelsBone MarrowS. Iron studiesReticulocyte count  <response>: Ans. d Reticulocyte countRef: Robbins 9thpg 645-648This is a tricky question as the initial investigation looks like B12 folate levels, as the patient has macrocytosis.But remember, Macrocytosis can also be seen in hemolytic anemia, as newer RBC precursors released are larger in size.So the initial investigation should be reticulocyte countIf reticulocyte is low it can be macrocytic anemia if there is reticulocytosis, then it can be a case of hemolytic anemia. 