Types of Diabetes
Type 1 Diabetes
Type 1 diabetes, previously known as insulin-dependent diabetes mellitus (IDDM) or juvenile-onset diabetes, is an autoimmune disease that occurs primarily in children and young adults; however, disease onset can occur at any age. An autoimmune disease occurs when the body’s system for fighting infection (the immune system) turns against a part of the body. In diabetes, the immune system attacks and destroys the insulin-producing beta cells in the pancreas. The pancreas then produces little or no insulin. A person who has type 1 diabetes must take insulin daily to live- either through injections or an insulin pump.
At present, scientists do not know exactly what causes the body’s immune system to attack the beta cells, but they believe that autoimmune, genetic and environmental factors, possibly viruses, are involved. Type 1 diabetes accounts for only about 5 to 10 percent of diagnosed diabetes in the United States.
Symptoms of type 1 diabetes usually develop over a short period, although beta cell destruction can begin years earlier. Symptoms may include increased thirst and urination, constant hunger, weight loss, blurred vision, and extreme fatigue. If not diagnosed and treated with insulin, a person with type 1 diabetes can lapse into a life-threatening diabetic coma, also known as diabetic ketoacidosis.
Type 2 Diabetes
The most common form of diabetes is type 2 diabetes. About 90 to 95 percent of people with diabetes have this form of diabetes. Type 2 diabetes is most often associated with obesity, family history of diabetes, previous history of gestational diabetes, physical inactivity, race/ethnicity and older age. About 80 percent of people with type 2 diabetes are overweight, and African Americans, Hispanic/Latino Americans, American Indians and some Asian Americans and Native Hawaiians or other Pacific Islanders are at particularly high risk for type 2 diabetes.
Type 2 diabetes is increasingly being diagnosed in children and adolescents, and if current trends continue, one in three children will develop type 2 diabetes in their lifetime.
- A blood glucose level of 126 milligrams per deciliter (mg/dL) or more after an 8-hour fast. This test is called the fasting blood glucose test.
- A blood glucose level of 200 mg/dL or more 2 hours after drinking a beverage containing 75 grams of glucose dissolved in water. This test is called the oral glucose tolerance test (OGTT).
- A random (taken at any time of day) blood glucose level of 200 mg/dL or more, along with the presence of diabetes symptoms.
When type 2 diabetes is diagnosed, the pancreas is usually producing enough insulin, but for unknown reasons, the body cannot use the insulin effectively, a condition called insulin resistance. Insulin production eventually decreases, and as a result, the amount of glucose in the blood increases, while the cells are starved of energy. Over the years, high blood glucose damages nerves and blood vessels, leading to complications, such as heart disease, stroke, blindness, kidney disease, nerve problems, gum infections and amputations.
The symptoms of type 2 diabetes develop gradually. Their onset is not as sudden as in type 1 diabetes. More than six million people in the United States have type 2 diabetes and do not know it. Many have no signs or symptoms. Symptoms can also be so mild that you might not even notice them. Some people have symptoms but do not suspect diabetes.
Gestational Diabetes
Some women develop gestational diabetes late in pregnancy. Although this form of diabetes usually disappears after the birth of the baby, women who have had gestational diabetes have a 20 to 50 percent chance of developing type 2 diabetes within five to 10 years. Maintaining a reasonable body weight and being physically active may help prevent development of type 2 diabetes.
About three to eight percent of pregnant women in the United States develop gestational diabetes. As with type 2 diabetes, gestational diabetes occurs more often in some ethnic groups and among women with a family history of diabetes. Gestational diabetes is caused by the hormones of pregnancy or a shortage of insulin. Women with gestational diabetes may not experience any symptoms.
Pre-Diabetes
Pre-diabetes is a term used to distinguish people who are at increased risk of developing diabetes. People with pre-diabetes have impaired fasting glucose (IFG) or impaired glucose tolerance (IGT). Some people may have both IFG and IGT.
IFG is a condition in which the fasting blood sugar level is elevated (100 to 125 milligrams per deciliter or mg/dL) after an overnight fast but is not high enough to be classified as diabetes.
IGT is a condition in which the blood sugar level is elevated (140 to 199 mg/dL) after a 2-hour oral glucose tolerance test, but is not high enough to be classified as diabetes.
In a cross-section of U.S. adults aged 40 to 74 years who were tested from 1988 to 1994, 33.8 percent had IFG, 15.4 percent had IGT, and 40.1 percent had pre-diabetes (IGT or IFG or both). When these percentages are applied to the 2000 U.S. population, about 35 million adults aged 40 to 74 would have IFG, 16 million would have IGT and 41 million would have pre-diabetes.
Progression to diabetes among those with pre-diabetes is not inevitable. Studies suggest that weight loss and increased physical activity among people with pre-diabetes prevent or delay diabetes and may return blood glucose levels to normal.
People with pre-diabetes are already at increased risk for other adverse health outcomes, such as heart disease and stroke.
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