1. Type 1 diabetes mellitus is characterized by loss of the
insulin-producing beta cells of the islets of Langerhans in
the pancreas leading to a deficiency of insulin.
2. Type 2: Results from Insulin resistance, a condition in
which cells fail to use insulin properly, sometimes
combined with relative insulin deficiency.
3. Gestational diabetes: Pregnant women who have never
had diabetes before but who have high blood sugar
(glucose) levels during pregnancy are said to have
gestational diabetes.
It may precede development of type 2 (or rarely type 1).