Diabetes is a condition in which the body cannot properly store and use sugar for energy. The body's main fuel is a form of sugar called glucose, which comes from food (after it's been broken down). Glucose enters the blood and is used by cells for energy. To use glucose, the body needs a hormone called insulin that's made by the pancreas. Insulin is important because it allows glucose to leave the blood and enter the body's cells.
Diabetes develops when the body can't make any or enough insulin, or when it can't properly use the insulin it makes. For some people with diabetes, the body becomes resistant to insulin. In these cases, insulin is still produced, but the body does not respond to the effects of insulin as well. Whether from not enough insulin or the inability to use insulin properly, the result is high levels of glucose in the blood, or hyperglycemia.
There are two main types of diabetes: type 1 diabetes and type 2 diabetes. About 90% of people with diabetes have the type 2 kind. Type 2 diabetes is also called noninsulin-dependent diabetes mellitus (NIDDM) or adult onset diabetes. Although children may have type 2 diabetes, it more commonly starts after age 30 and becomes more common with age. About 15% of people over 70 have type 2 diabetes.
Some people do not have diabetes, but do not handle glucose as well as normal. This is called impaired glucose tolerance (IGT). Up to 40% of people with IGT will eventually develop type 2 diabetes.
In type 2 diabetes, either the pancreas does not make enough insulin or the body does not use it properly. No one knows the exact cause of type 2 diabetes, but it's more likely to occur in people who:
- are over 40 years of age
- are overweight
- have a family history of diabetes
- developed gestational diabetes during a pregnancy
- have given birth to a baby that is more than 9 lbs (4 kg)
- have high blood pressure
- have high cholesterol
- have IGT or impaired fasting glucose
- are of Native American, Hispanic, Asian, South Asian, or South African descent