Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Type 2 Diabetes Mellitus

What Is It?

Type 2 diabetes is a chronic disease. It is characterized by high levels of sugar in the blood. Type 2 diabetes is also called type 2 diabetes mellitus, adult-onset diabetes, non-insulin-dependent diabetes, or just diabetes.

Type 2 diabetes affects the way the body processes and uses carbohydrates, fats and proteins. During digestion, food is broken down into its basic components. The liver processes these nutrients into one type of sugar—glucose. Glucose is the most basic fuel for the body.

Glucose enters your body's cells with the help of insulin. Insulin is a hormone produced by the pancreas. Without insulin, glucose cannot pass through the cell wall.

Type 2 diabetes occurs when your body's cells do not react efficiently to insulin. This condition is called insulin resistance.

In people with insulin resistance, the pancreas first makes extra insulin to maintain a normal blood sugar. Over time, the body's insulin resistance gets worse. The pancreas cannot keep up with the demand for more and more insulin. As a result, blood glucose levels rise.

Type 2 diabetes runs in families. It most often affects people who are older than 40. But type 2 diabetes is now being seen in more and more young people. Obesity greatly increases the risk of diabetes.