One should ideally take up a home science course after finishing school. It is always better to have done science in your 11th and 12th. Then you should pursue a master’s in the same course with “food science and nutrition” as your specialisation.If you are a graduate in Microbiology, Chemistry, Home Science, Hotel Management etc you can pursue a 2 year long M.Sc in Nutrition. Another option is to pursue a 1 year PG diploma course in Nutrition and Dietitics.
In order to become a registered dietician you have to clear a Registered Dietician (RD) exam that is conducted every year by the IDA (Indian Dietetic Association). This has to be followed by a 6 month long internship at a hospital recognised by the IDA.