How is the disease diagnosed?
A doctor may suspect diabetes after taking a person's health history and
doing a physical exam. Based on those results, the doctor may want to check for a
high glucose level in the blood. There are several types of blood tests doctors can
use to diagnose diabetes, including:
fasting plasma glucose test,
which is the most common method to diagnose most cases of diabetes. In this test,
a person is asked to fast overnight for at least 8 hours. In the morning, the level of
glucose in the blood is then checked. Healthy fasting plasma glucose levels are
less than 110 milligrams per deciliter or mg/dL. A fasting plasma glucose level of
more than 126 mg/dL usually suggests diabetes. Levels between 110 and 126 mg/dL
are seen in prediabetes.
oral glucose tolerance test,
which is the preferred way to diagnose gestational diabetes.
It can also be used to diagnose type 2 diabetes and prediabetes. In this test, a
person is asked to drink a sweet liquid. Blood samples are then drawn at timed
intervals. If a person does not have diabetes, the glucose levels will rise and then
fall quickly after drinking the sweet liquid. When a person has diabetes, glucose
levels will rise higher and fail to come down as fast as those in a person without
diabetes. If the blood glucose level is 140 to 199 mg/dL 2 hours after drinking the
liquid, a diagnosis of prediabetes can be made.
plasma glucose test,
which can be done without fasting and is used as a screening tool. A level of
200 mg/dL or higher suggests diabetes. If the level is above 200 mg/dL on two separate days,
a fasting glucose test or oral glucose tolerance test
can be done to confirm the diagnosis of diabetes.
