Pre-diabetes is a condition of high blood glucose levels, but not yet high enough for diagnosis of diabetes. Those with pre-diabetes are at increased risk of developing Type 2 diabetes, heart disease and stroke. Moderate-intensity physical activity and weight loss can delay or prevent the development of Type 2 diabetes. It is estimated that approximately 79 million Americans have pre-diabetes.

Previously known as juvenile diabetes or insulin-dependent diabetes, Type 1 diabetes results when the pancreatic beta cells are destroyed by the immune system. Beta cells are the only cell type in the body capable of producing insulin, so the loss means a person is no longer able to make insulin and no longer able to regulate the levels of blood sugar. These patients are dependent on insulin replacement given by injection or an insulin pump. Type 1 diabetes is the most commonly diagnosed type of diabetes in children, adolescents, and young adults. Overall, it accounts for approximately 5-10 percent of all diabetes cases. Risk factors for development of Type 1 diabetes are a combination of genetic and environmental factors.

Previously known as adult-onset diabetes or non-insulin dependent diabetes, Type 2 diabetes is a progressive disease caused by a combination of insulin resistance, an inability of pancreatic beta cells to produce adequate amounts of insulin and ultimately beta cell death. This form of diabetes accounts for approximately 90 to 95 percent of diabetes cases. It is most often observed in older adults, but cases in children and young adults are increasing. The risk factors for developing Type 2 diabetes include older age, obesity, family history, low physical activity, unhealthy diet with high fat and sugary foods, and race/ethnicity.

Diabetes that develops during pregnancy is called gestational diabetes. An expectant mother would experience all the symptoms of diabetes, such as thirst and fatigue. While the diabetes typically disappears after giving birth, the mother is at increased risk of developing diabetes later in life. Also, the health of the baby depends on the mother being able to tightly control her blood sugar levels.

Type 1 and Type 2 diabetes occur most often and are described as polygenic, which means several genes are causing it. In rarer forms, which represent about one to two percent of all cases, a single gene that has mutated can cause diabetes. The gene could be inherited or just mutate on its own. These diabetic conditions are called monogenic and the most common example in this group is maturity-onset diabetes of the young (MODY). Patients affected will often have multiple family members who developed diabetes at an early age and some could benefit from special therapies.