The period from three weeks before parturition until three weeks after parturition in dairy cows is defined as transition period. It is considered the most critical period, in terms of health, production and profitability as most of the metabolic and infectious diseases occur during this period. This period is characterised by negative energy balance (NEB), when an animal fails to metabolically adapt to the NEB, it suffers from metabolic disorders. High NEFA concentrations and ROS production are characteristics of metabolic stress and have been recognized as risk factors for diseases in transition cows. A smooth transition period indicates high productive and reproductive performance in dairy animals; on the contrary poor transition indicates compromised production and reproduction which cause tremendous economic loss to livestock farmers. An understanding about the physiological changes occurring in dairy animals during transition would go a long way in improving the feeding and management practices to enhance production.