Prediabetes often preceeds Type 2 diabetes. Blood sugars are elevated, but not high enough to diagnose Type 2 diabetes.
Type 1 diabetes differs from Type 2 as it is an autoimmune disease, which destoys insulin producing betacells. People with Type 1 diabetes are dependent on insulin. It primarily affects children, although it can develop in adulthood.
Type 2 diabetes occurs when insulin production declines or when the body is resistant to insulin. Adulthood onset is typical, however, incidence is rising in younger people.
Gestational diabetes occurs during pregnancy, and is often associated with developing Type 2 diabetes later in life.