There are several types of diabetes. Most forms of diabetes are chronic — lasting throughout life, treatable but not curable. Diabetes is technically called diabetes mellitus, although this term is not used as commonly.
Type 2 diabetes is the most common form of diabetes. Approximately 34 million people in the U.S., or almost 1 in 10 people, have type 2 diabetes. Not everyone with diabetes has been diagnosed; it is estimated that one-third of those with diabetes may not realize they have it. Type 2 diabetes is most commonly diagnosed in adults age 45 or older but may also occur in younger adults and children.
In type 2 diabetes, the body produces insulin, the hormone necessary for cells to use glucose in the blood for fuel. As type 2 develops, the cells gradually become resistant to insulin. Cells can no longer take up glucose, and blood glucose levels rise, causing damage to nerves, blood vessels, and organs.
Type 2 is caused by a combination of genetic and environmental factors. Although family history and ethnic background can increase or decrease risk for developing the disease, factors including overweight or obesity, sedentary lifestyle, and unhealthy diet strongly promote the development of type 2 diabetes. Read more about causes of type 2 diabetes.
Some people with type 2 diabetes manage their condition with medications, diet, and exercise and do not take insulin, while those with more severe diabetes require insulin injections.
Doctors diagnose prediabetes (also called impaired glucose tolerance or impaired fasting glucose) when blood glucose test results are higher than normal, but not yet as high as those seen in type 2 diabetes. Prediabetes indicates that someone is becoming insulin resistant and may progress to type 2 diabetes without treatment. Prediabetes can often be reversed with significant weight loss, diet changes, and an increase in exercise. Medication may also be prescribed.
Only about 5 percent of people with diabetes have type 1, previously known as juvenile diabetes. Type 1 diabetes is usually diagnosed in children or young adults. In type 1, the body does not produce insulin. Type 1 diabetes is caused by an autoimmune reaction, wherein the body’s immune system mistakenly identifies insulin-producing cells as a threat and destroys them. People with type 1 are dependent on insulin treatment and cannot live without it.
Between 2 percent and 10 percent of women develop gestational diabetes when they are pregnant. Testing for gestational diabetes is a standard part of prenatal care for pregnant women. Women are usually tested in the second trimester, but may be tested earlier if they have risk factors such as a high body mass index (BMI) or a family history of diabetes. Gestational diabetes may not cause diabetes symptoms, but it can cause pregnancy and birth complications and raise the risk that the child will later develop obesity and type 2 diabetes.
Gestational diabetes typically disappears after pregnancy. However, about 50 percent of women who have gestational diabetes during pregnancy develop type 2 diabetes later on. Between 30 percent and 69 percent of women who have gestational diabetes during one pregnancy go on to develop the condition during a subsequent pregnancy.
Not a type of diabetes mellitus, diabetes insipidus is a rare condition usually caused by problems in the brain or kidneys. Similar to diabetes mellitus, diabetes insipidus causes excessive thirst and urination. Diabetes mellitus and diabetes insipidus were named in the Middle Ages, when doctors commonly tasted patient’s urine for clues about the sickness. Mellitus is Latin for “honey,” indicating that the urine of people with this type of diabetes tastes sweet. Insipidus is Latin for “tasteless,” indicating that the urine of people with this type had no flavor. Diabetes insipidus is not curable, but it is treatable.