Diabetes Diagnosis: How Doctors Determine It's Diabetes

There are two laboratory blood tests used to arrive at a diabetes diagnosis:

The first is called a fasting plasma glucose test. This test requires a blood sample after an overnight fast (no eating or drinking for eight hours). If the person you're caring for has symptoms that indicate diabetes and her fasting blood sugar reading is above 126 milligrams per deciliter of blood (mg/dL), diabetes is diagnosed.

The second test is known as the oral glucose tolerance test. After an overnight fast, a patient will be given a blood test and, immediately afterward, a sugary beverage to drink. Another blood sample is taken two hours later. If the initial blood sugar reading is above 126 mg/dL and/or her two-hour test result is above 200 mg/dL, the doctor can make a diabetes diagnosis.


Sarah Henry

Sarah Henry has covered health stories for most of her more than two decades as a writer, from her ten-year stint at the award-winning Center for Investigative Reporting to her staff writer position with Hippocrates magazine to her most recent Web work for online sites, including WebMD, Babycenter. See full bio

over 3 years, said...

I have Diabetes and I understand it is determined by your blood sugar level, but I was never told what the level was that makes the determination.

over 4 years, said...

Make sure you bug your doctor for periodic tests for Diabetes if you've had a very large baby or had Gestational Diabetes. As I understand it, G.D. increases your risk for Type 2 diabetes, but not many doctors seem to know about this. My "baby" was 14 when I was diagnosed, and the new doctor who had me tested was astonished that no one had checked my blood sugar after I had my baby. If I had known, I'd have probably been a lot more diligent about my diet and keeping up with exercise.