Diabetes is a disease that's characterized by high blood sugar, which doctors refer to as hyperglycemia.

What makes type 2 diabetes different from type 1 diabetes, gestational diabetes, and other types of diabetes is the underlying cause of high blood sugar.

In type 2 diabetes, the two main contributors to high blood sugar are insulin resistance and reduced production of insulin by the pancreas.

Prevalence of Diabetes

  • More than 29 million people in the United States - almost 10 percent of the total population - have diabetes, according to the Centers for Disease Control and Prevention (CDC).
  • The vast majority of those people (90 to 95 percent) have type 2 diabetes.
  • About 8.1 million people with diabetes are undiagnosed.
  • Diabetes is now the seventh leading cause of death among Americans, according to the CDC.
  • If current trends continue, one of every three adults in the United States will have some form of diabetes by 2050.
  • The CDC also estimates there were 1.7 million newly diagnosed cases of diabetes among people aged 20 and older in the United States in 2012 (the most recent year for which statistics are available).
  • Worldwide, about 347 million people currently have diabetes, according to the World Health Organization (WHO). And children, who were rarely diagnosed with type 2 diabetes in the past, now account for a growing proportion of those diagnosed with type 2 diabetes.

Insulin Resistance

Insulin resistance is a state in which the body’s cells do not use insulin efficiently. As a result, it takes more insulin than normal to transport glucose (the main type of sugar found in the bloodstream) into cells, where it can be used for fuel or stored for later use.

It’s not entirely clear why some people develop insulin resistance and others don’t. Obesity, which is the main risk factor for developing type 2 diabetes, is known to increase insulin resistance.

But not all people with type 2 diabetes are obese — and not all obese people develop the condition — so other issues such as genetics are contributing factors as well.

Reduced Insulin Production

Insulin resistance develops over time, and as the body becomes more and more insulin resistant, the pancreas responds by releasing more and more insulin. This higher-than-normal level of insulin in the bloodstream is called hyperinsulinemia.

For a while, the pancreas may be able to keep up with the body’s increased need for insulin, and blood sugar levels may stay within the normal range — about 70 to 100 mg/dl before meals and lower than 140 mg/dl after meals. Eventually, however, the pancreas can no longer keep up, and blood sugar levels begin to rise.

In the early stages, higher-than-normal blood sugar may cause no symptoms. But catching it early is important, because over time, high blood sugar can have negative effects on just about every part of the body.

Screening Tests for Type 2 Diabetes

Currently, the American Diabetes Association recommends that everyone get screened for diabetes beginning at age 45. People who have risk factors besides age (the risk of type 2 diabetes rises with age) should get screened earlier.

The two types of blood tests most commonly used to screen for type 2 diabetes: fasting plasma glucose test and the HbA1c test (also called the A1C test or the hemoglobin A1c test).

The fasting plasma glucose test requires fasting for 8 to 10 hours before blood is drawn. The test result shows the blood sugar level at the time the test was done. A result of 126 mg/dl or higher indicates diabetes. In a person with no other signs or symptoms of hyperglycemia, the test should be repeated on another day to confirm the diagnosis.

The HbA1c test does not require fasting before the test. The test result reflects the average blood sugar level in the blood over the previous two to three months. A test result of 6.5 percent or higher indicates diabetes.

Like the fasting plasma glucose test, in a person with no other signs or symptoms of hyperglycemia, the test should be repeated on another day to confirm the diagnosis.

Treating Type 2 Diabetes

Treatment for type 2 diabetes includes dietary changes, regular physical activity, and usually one or more blood-sugar-lowering drugs. Most people start with the oral diabetes drug metformin (Fortamet, Glucophage, Glucophage XR, Glumetza), then increase the dose of metformin or add other oral drugs as needed to maintain blood sugar control.

Several new injected drugs can also be effective at helping to control blood sugar.

Although type 2 diabetes used to be called non-insulin-dependent diabetes, many people with type 2 diabetes eventually need to use insulin for optimal blood sugar control. This occurs because the pancreas can no longer produce enough insulin to keep up, not because you don’t try hard enough to control your blood sugar.

Everyone’s type 2 diabetes treatment is different — and will likely change over time due to age and lifestyle choices.