There are two main types of diabetes mellitus.Type IType I diabetes (also called insulin - dependent diabetes mellitus, or IDDM) takes place whenever the pancreatic cells in the do not do its work and they produce less than the needed insulin. If the pancreas does not even make insulin, the sugar cannot be utilized by the tissues.To stay alive, the majority of these people will have to depend on insulin injections for the rest of their lives. Type I is the much less common form of diabetes — only about 10 - 20 per cent of all diabetics are insulin - dependent. This kind of diabetes usually begins in childhood or youth.Type IIType II diabetes (also called non - insulin - dependent diabetes mellitus, or NIDDM) usually occurs in overweight individuals who are beyond the age of 40. In Type II diabetes, the pancreas does still produce some insulin. There are instances that the body is simply not making enough insulin. In other instances, though, the pancreatic cells are producing normal levels of insulin, but that insulin is no longer useable since the cells' insulin receptors — the "locks" — are shut closed. The pancreatic cells react to this scenario by making lots and lots of insulin. But when the receptors are not functional, even this cannot remedy it.