A number of procedures are available to test for diabetes. Most of them are blood tests that seek to confirm high blood sugar levels when compared to normal blood sugar levels. Urine tests are often used as a screening test for diabetes since high blood sugar often results in sugar spilling into the urine.
Here are the four most common diabetes tests and what their results mean.
Fasting Plasma Glucose Test
One of the more common tests for diabetes, the fasting plasma glucose test, measures blood sugar after a 12 to 14 hour fast. Fasting prompts the body to release glucagon, a hormone that acts to raise normal blood sugar levels. In the non-diabetic, insulin is released to bring the high blood sugar back down to a normal level. This doesn’t occur in the body of a person with diabetes. Normal blood sugar levels after a fast should be in the range of 70–100 mg/dl. A blood sugar reading of 126 mg/dl or higher suggests diabetes, and the test will often be repeated. If the blood sugar results of a second test measure 126 mg/dl or higher, a diagnosis of diabetes is usually confirmed.
Oral Glucose Tolerance Test
Like the fasting plasma glucose test, an oral glucose tolerance test is performed after fasting. The patient drinks a glucose solution, and blood tests are taken several times over the course of a three-hour period. If insulin production is within normal limits, blood sugar should rise over the first hour to 160-180 mg/dl, and then drop back to normal. If diabetes is present, the high blood sugar level will take much longer to drop. Any blood sugar result that is 200 mg/dl or higher is indicative of diabetes.
Random Plasma Glucose Test
A random plasma glucose test is just that: random. It can be done at any time, although results are not always as conclusive or reliable as the fasting tests. A result of 200 mg/dl or more indicates diabetes.
Urine testing measures the level of glucose in the urine, and positive results can indicate diabetes. Using urine to measure glucose levels is not as effective or precise as blood tests, however. Urine testing is more commonly performed to examine ketone levels. When the body doesn’t have access to glucose for energy, it begins to break down fats. Ketones are chemical compounds that result from the breakdown of fat. They are toxic, and can kill cells. Left unchecked, high levels of ketones can cause diabetic coma. (Find out more about Diabetic Complications.)