Diabetes is caused by a problem in the way your body makes or uses insulin. Insulin is needed to move blood sugar (glucose) into cells, where it is stored and later used for energy.
When you have type 2 diabetes, your fat, liver, and muscle cells do not respond correctly to insulin. This is called insulin resistance. As a result, blood sugar does not get into these cells to be stored for energy.
When sugar cannot enter cells, high levels of sugar build up in the blood. This is called hyperglycemia.
Type 2 diabetes usually occurs slowly over time. Most people with the disease are overweight when they are diagnosed. Increased fat makes it harder for your body to use insulin the correct way.
Type 2 diabetes can also develop in people who are thin. This is more common in the elderly.
Family history and genes play a large role in type 2 diabetes. Low activity level, poor diet, and excess body weight around the waist increase your risk.