A 30 year old female patient complains of weakness and fatigue. Patient gives history of consumption of antiepileptic drugs and is also a lactating mother. Lab investigation reveals Hb-8gm% and presence of macrocytic RBCs on peripheral blood smear. This patient may be suffering from deficiency of-

The folic acid deficiency(vitamin B9) may be due to (one or more causes) inadequate dietary intake, defective  absorption, use of anti convulsant drugs (phenobarbitone, dilantin, phenytoin), and increased  demand.  The rapidly dividing cells of bone marrow are seriously affected.  The macrocytic anemia  (abnormally large RBC) associated with megaloblastic changes in bone marrow is a characteristic  feature of folate deficiency. Satyanarayana- Biochemistry, 3rd edition, pg-152