How does a doctor identify diabetes? Once symptoms appear, type 1 diabetes
rarely goes undiagnosed for more than a few weeks. The most important clue
is frequent urination, sometimes accompanied by feeling thirsty all the time,
poor weight gain, or flu-like symptoms. If you and your doctor suspect diabetes,
testing is necessary to confirm the diagnosis. There are two tests done to
check for blood sugar levels.
Random blood glucose test
A random blood, or plasma, glucose test can be done at any time, regardless
if you have eaten or not. A blood sample is drawn from the arm or the back
of the hand and analyzed for glucose level. If the glucose level is greater
than or equal to 200 mg/dL, it generally means the person has diabetes. Glucose
in the urine is strong additional evidence.
However, a random blood glucose test below this level does not eliminate the
possibility of diabetes.
Fasting plasma glucose (FPG) test
This is the recommended diagnostic test for diabetes. "Fasting" means that
no food can be eaten for 8 - 12 hours prior to the test -- only water may be
consumed. A blood sample is drawn in the same manner as the random test.
If there is any doubt that a patient truly has diabetes, two or more FPG tests
may be done on different days to verify the results.
What does the FPG test reveal?
Normal fasting glucose levels are lower than 100 mg/dL. Patients whose glucose
is between 100 mg/dL and 126 mg/dL have "impaired fasting glucose" and are
at risk for developing type 2 diabetes, although they do not yet have diabetes.
When fasting glucose levels are 126 mg/dL or higher, the patient has diabetes.
Usually, at the moment of diagnosis, people with type 1 diabetes have glucose
levels that are "off the charts," often higher than 400 mg/dL. It is very important
to see a doctor right away if you suspect diabetes.
American Diabetes Association. Diagnosis and classification of diabetes mellitus. Diabetes
Care 2007;30(suppl 1):542-547.
McPhee SJ, Papadakis MA, Tierney LM eds. Current Medical Diagnosis & Treatment
2007. 46th ed. New York: Lange Medical Books/McGraw-Hill, 2007.
Review Date: 5/10/2007
Reviewed By: Robert Hurd, MD, Professor of Endocrinology, Department of Biology, Xavier University, Cincinnati, OH. Review provided by VeriMed Healthcare Network.
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