After a patient has been diagnosed with diabetes mellitus, a physician determines the type so that treatment can begin. In some cases, a physician can determine the type only after evaluating the patient’s initial response to treatment.

The four types are -

a) Type 1, or insulin-dependent diabetes mellitus.

b) Type 2, or non-insulin-dependent diabetes mellitus.

c) Gestational diabetes mellitus.

d) Diabetes secondary to other medical conditions.

Borderline and chemical diabetes are now called impaired glucose tolerance and aren’t classified as diabetes at all.

Type 1 Diabetes Mellitus

Patients with Type 1 diabetes produce no insulin, and their blood glucose levels can be controlled only with daily insulin injections. These patients account for about 10% of all those with diabetes. Previously called juvenile-onset diabetes, Type 1 generally appears before age 30, but it appears most commonly during early adolescence. The disease may appear slightly earlier in females than in males.

The signs and symptoms of Type 1 diabetes seem to begin abruptly. Patients with Type 1 dia­betes are prone to DKA and are at risk for developing vascular complications.

No one fully understands what causes Type 1 diabetes. Some theories suggest a genetic susceptibility linked to an environmental trigger. Genetic studies have shown that a family history of Type 1 diabetes may put a person at risk for developing the disease. Yet, about 80% of children with Type 1 diabetes have no family history of the disease. Human leukocyte antigens, which appear on genes that control immune response, may cause the genetic susceptibility. However, many people have these antigens and never develop diabetes.

Various environmental causes may trigger diabetes in a person who’s genetically susceptible to the disease. For example, children who drink cow’s milk at a young age may be at increased risk for developing Type 1 diabetes because of an autoimmune response to milk proteins. Viruses also seem to play a role in triggering diabetes. The disease appears more commonly in the fall and winter during viral outbreaks, but the time between exposure to the virus and the first signs and symptoms of diabetes makes it difficult to identify the triggering virus.

Islet cell antibodies also have been linked to Type 1 diabetes. Some patients with Type 1 diabetes have islet cell antibodies years before their symptoms begin. These antibodies cause active autoimmunity against beta cells-the cells that produce insulin.

Despite the many theories about the cause of Type 1 diabetes, there’s no way to predict who will develop the disease.