This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
A 30 year old female epileptic on phenytoin, developed weakness and fatigue. Blood examination revealed Hb = 4.6 gm. MCV = 102 fl and MCH = 40 pg/dl. What is the most probable diagnosis ? 
Select and explain. 
A. Hea failure, B. Iron deficiency anaemia, C. Phenytoin induced agranulocytosis, D. Megalobalstic anaemia
D: Megalobalstic anaemia
Answer: D: Megalobalstic anaemia 
Explanation: Ans. is 'd' i.e., Megalablostic anaemia Raised MCV (normal 86-98) and MCH (normal 28-33) with low hemoglobin (normal 12-16) suggest the diagnosis of megaloblastic anemia. Remember Amongst antiepileptics, phenytoin, phenobarbitone and primidone can cause megaloblastic anemia.