Insulin is involved in regulation of glucose utilization in the body. Inability of the body to synthesize insulin of human cells resistance to insulin leads to a condition called Diabetes mellitus which is characterized by chronic hyperglycaemia. There are two types of diabetes; type 1 and type 2. Exogenous supply of insulin is needed consistently for type 1 diabetes treatment and type 2 diabetes also needs to be cured by the exogenous supply of insulin in advance stages of the disease. These sources have been proved very useful to meet the needs of the patients. However, these insulin types are expensive for the large population of patients in the developing countries. Furthermore, the incidence of diabetes is advancing at an alarming rate. Hence production systems with even higher capabilities of production are desired. Therefore, currently plants are being investigated as alternative production systems. Based on the mode of action of insulin various formulations of insulin have been developed that have different onset of action, peak effect and duration of action according to the needs of the patients.