Almost everyone knows someone who has diabetes. An estimated 18.2 million
people in the United States—6.3 percent of the population—have diabetes, a
serious, lifelong condition. Of those, 13 million have been diagnosed, and about
5.2 million people have not yet been diagnosed. Each year, about 1.3 million
people aged 20 or older are diagnosed with diabetes.
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What is diabetes?
Diabetes is a disorder of metabolism—the way our bodies use digested food for
growth and energy. Most of the food we eat is broken down into glucose, the form
of sugar in the blood. Glucose is the main source of fuel for the body.
After digestion, glucose passes into the bloodstream, where it is used by
cells for growth and energy. For glucose to get into cells, insulin must be
present. Insulin is a hormone produced by the pancreas, a large gland behind the
stomach.
When we eat, the pancreas automatically produces the right amount of insulin
to move glucose from blood into our cells. In people with diabetes, however, the
pancreas either produces little or no insulin, or the cells do not respond
appropriately to the insulin that is produced. Glucose builds up in the blood,
overflows into the urine, and passes out of the body. Thus, the body loses its
main source of fuel even though the blood contains large amounts of
glucose.
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What are the types of diabetes?
The three main types of diabetes are
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- type 1 diabetes
- type 2 diabetes
- gestational diabetes
Type 1 Diabetes
Type 1 diabetes is an autoimmune disease. An autoimmune disease results when
the body’s system for fighting infection (the immune system) turns against a
part of the body. In diabetes, the immune system attacks the insulin-producing
beta cells in the pancreas and destroys them. The pancreas then produces little
or no insulin. A person who has type 1 diabetes must take insulin daily to
live.
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 about 5 to 10 percent of diagnosed diabetes in the United States. It
develops most often in children and young adults, but can appear at any age.
Symptoms of type 1 diabetes usually develop over a short period, although
beta cell destruction can begin years earlier. Symptoms 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 type 2. This form of diabetes is associated with
older age, obesity, family history of diabetes, previous history of gestational
diabetes, physical inactivity, and ethnicity. About 80 percent of people with
type 2 diabetes are overweight.
Type 2 diabetes is increasingly being diagnosed in children and adolescents.
However, nationally representative data on prevalence of type 2 diabetes in
youth are not available.
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. After several years, insulin production
decreases. The result is the same as for type 1 diabetes—glucose builds up in
the blood and the body cannot make efficient use of its main source of fuel.
The symptoms of type 2 diabetes develop gradually. Their onset is not as
sudden as in type 1 diabetes. Symptoms may include fatigue or nausea, frequent
urination, unusual thirst, weight loss, blurred vision, frequent infections, and
slow healing of wounds or sores. Some people have no symptoms.
Gestational Diabetes
Gestational diabetes develops only during pregnancy. Like type 2 diabetes, it
occurs more often in African Americans, American Indians, Hispanic Americans,
and among women with a family history of diabetes. Women who have had
gestational diabetes have a 20 to 50 percent chance of developing type 2
diabetes within 5 to 10 years.
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What are the tests for diagnosing diabetes?
The fasting plasma glucose test is the preferred test for diagnosing type 1
or type 2 diabetes. It is most reliable when done in the morning. However, a
diagnosis of diabetes can be made after positive results on any one of three
tests, with confirmation from a second positive test on a different day:
- A random (taken any time of day) plasma glucose value of 200 mg/dL or more,
along with the presence of diabetes symptoms. - A plasma glucose value of 126 mg/dL or more after a person has fasted for 8
hours. - An oral glucose tolerance test (OGTT) plasma glucose value of 200 mg/dL or
more in a blood sample taken 2 hours after a person has consumed a drink
containing 75 grams of glucose dissolved in water. This test, taken in a
laboratory or the doctor’s office, measures plasma glucose at timed intervals
over a 3-hour period.
Gestational diabetes is diagnosed based on plasma glucose values measured
during the OGTT. Glucose levels are normally lower during pregnancy, so the
threshold values for diagnosis of diabetes in pregnancy are lower. If a woman
has two plasma glucose values meeting or exceeding any of the following numbers,
she has gestational diabetes: a fasting plasma glucose level of 95 mg/dL, a
1-hour level of 180 mg/dL, a 2-hour level of 155 mg/dL, or a 3-hour level of 140
mg/dL.
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What are the other forms of impaired glucose metabolism
(also called pre-diabetes)?
People with pre-diabetes, a state between “normal” and “diabetes,” are at
risk for developing diabetes, heart attacks, and strokes. However, studies
suggest that weight loss and increased physical activity can prevent or delay
diabetes. There are two forms of pre-diabetes.
Impaired Fasting Glucose
A person has
impaired fasting glucose (IFG) when fasting plasma glucose is 100 to 125 mg/dL.
This level is higher than normal but less than the level indicating a diagnosis
of diabetes.
Impaired Glucose Tolerance
Impaired glucose tolerance (IGT) means that blood glucose during the oral
glucose tolerance test is higher than normal but not high enough for a diagnosis
of diabetes. IGT is diagnosed when the glucose level is 140 to 199 mg/dL 2 hours
after a person drinks a liquid containing 75 grams of gluc
