Background:–Vitamin B12 deficiency is a common cause of macrocytosis that leads to megaloblasticanemia in Indian population with different clinical profiles. But there are many other conditions that can mimic B12 deficiency and can lead to macrocytic anemia.

Objectives:– This study is an attempt to correlate serum Vitamin B12 level with macrocytic anemia, so that it can be treated early and complications like neurological manifestations and circulatory failure can be prevented, and anemia can be typified.

Methods:– In this prospective study datacollected from 100 patients, with prior consent, having macrocytic anemia admitted in our hospital over period of 1 year and results analyzed.

Results:– Pure B12 deficiency was the major cause of macrocytic anemia. It was found mainly in lacto vegetarians and in middle age group. Males were more affected than females. Neurological manifestations were seen only in 3.7%. Only 20% of patients were having other causes of macrocytic anemia like liver disease, Hypothyroidism, Zidovudine induced, HemolyticAnemia, Iron+B12 deficiency.

Conclusion:– We concluded that B12 deficiency, seen mainly in middle aged males and in lacto vegetarians, was the main cause of macrocytosis. But other conditions like Alcoholic liver disease, Non alcoholic fatty liver disease, Hypothyroidism, Zidovudine, Iron+B12 deficiency, Hemolysis can also lead to macrocytic anemia.