Diabetes Mellitus type one is when the beta cells can't produce insulin and is treatable by injection of insulin. what is the difference between diabete mellitus type one and diabetes mellitus type 2 in terms of the symptons and treatment? I thought diabetes mellitus type 2 is even if the body is given injection of insulin, the body will reject it. and to treat it by tablets that are composed of insulin or it is also treatable by diet and exercise. is that the jist of it.