There are several forms of diabetes, but the best known are types 1 and 2. Type 1 is an autoimmune disease in which the body produces too little insulin itself. The immune system destroys the cells that do this. People with this form must therefore give themselves insulin.
Type 2 is also called a lifestyle disease. In type 2, the body no longer responds well to insulin: this is called insulin insensitivity. This form of diabetes is the most common: 9 out of 10 people with diabetes have type 2. People with type 2 usually receive nutritional and exercise advice, sometimes supplemented with insulin.