Screening Tests

There are no clear-cut guidelines for when to screen for diabetes. Some experts recommend that everyone over age 45 be tested regularly for diabetes, although others do not feel this necessary in people without symptoms or risk factors. In fact, early screening may identify some people with impaired glucose levels that would eventually normalize. Such people might be treated unnecessarily with medications that pose a risk for high blood sugar (hypoglycemia).

Still, given the risk for serious complications with diabetes and the potential value of early treatments, most experts recommend that all adults over 45 be screened and that younger adults be screened if they have one or more of the following conditions:

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A weight that is 20% more than ideal body weight
Risk factors for heart disease (high blood pressure, unhealthy cholesterol levels -- especially for patients with low HDL cholesterol and high triglyceride levels
A close relative with diabetes
A high-risk ethnic group background
In women, having delivered a baby weighing over 9 pounds or having a history of gestational diabetes

Some experts recommend that children over age 10 should be tested for type 2 diabetes (even if they have no symptoms), if they are overweight and have at least two of the above mentioned risk factors.

Testing for Diabetes

Fasting Plasma Glucose. The fasting plasma glucose (FPG) test is the standard test for diabetes. It is a simple blood test taken after 8 hours of fasting. Results indicate:

FPG levels are considered normal up to 100 mg/dL (or 5.5 mmol/L).
Levels between 100 and 125 mg/dL (5.5 to 7.0 mmol/L) are referred to as impaired fasting glucose or pre-diabetes. These levels are considered to be risk factors for type 2 diabetes and its complications.
Diabetes is diagnosed when FPG levels are 126 mg/dL (7.0 mmol/L) or higher.

The FPG test is not always reliable, so a repeat test is recommended if the initial test suggests the presence of diabetes, or if the test is normal in people who have symptoms or risk factors for diabetes. For example, people who take the test in the afternoon and show normal results may actually have abnormal levels that would be revealed if they were tested in the morning.