It is a type of peptide hormone produced by the beta cells of the pancreas and is responsible for regulating carbohydrates and fat metabolism in the body. Insulin regulates the absorption of glucose by the liver,skeletal muscles and fat tissues from the blood. It is important that excess glucose is removed from the body, otherwise it can be toxic — insulin plays an important part in making this happen. In cases where there is a lack of insulin in the blood the body starts to use stored sugar as a source of energy. People with diabetes mellitus or type 2 diabetes, have a lack of insulin in the blood and a medical form of the insulin is used to replace it. In the case of type 1 diabetes patients are administered insulin externally.