Hi Hema, 

In government medical colleges of any state as far as i know there is no fee concession for any reserved category i.e sc, st or obc category. However what is there is scholarship schemes Which has a eligibility criteria for being from a low income group family that is the family income should be less than approx 9000 per annum. ( this is the criteria of my college scholarship scheme, i belong to a govt. medical college in west bengal ) . Also you need to maintain a minimum of 50% marks in the subjects of every year in order to enjoy the scholarship scheme throughout your college life. 

Hope this helped. All the best. :)