American Diabetes Association defines the four major types of diabetes as follows:
Type 1 diabetes
Results from the body’s failure to produce insulin, the hormone that “unlocks” the cells of the body, allowing glucose to enter and fuel them. It is estimated that 5-10% of Americans who are diagnosed with diabetes have type 1 diabetes.

Type 2 diabetes
Results from insulin resistance (a condition in which the body fails to properly use insulin), combined with relative insulin deficiency. Most Americans who are diagnosed with diabetes have type 2 diabetes.

Gestational diabetes
Immediately after pregnancy, 5% to 10% of women with gestational diabetes are found to have diabetes, usually, type 2.

Pre-diabetes
Pre-diabetes is a condition that occurs when a person’s blood glucose levels are higher than normal but not high enough for a diagnosis of type 2 diabetes. There are 57 million Americans who have pre-diabetes, in addition to the 23.6 million with diabetes.