Diagnosis of Diabetes

Positive test results should be confirmed by repeating the fasting plasma glucose test or the oral glucose tolerance test on a different day. When first diagnosed with diabetes, your doctor may suggest a zinc transporter 8 autoantibody (ZnT8Ab) test. This blood test — along with other information and test results — can help determine if a person has type 1 diabetes and not another type. The goal of having the ZnT8Ab test is a prompt and accurate diagnosis and that can lead to timely treatment.

Fasting Plasma Glucose (FPG) Test

The FPG is most reliable when done in the morning. Results and their meaning are shown in table 1. If your fasting glucose level is 100 to 125 mg/dL, you have a form of prediabetes called impaired fasting glucose (IFG), meaning that you are more likely to develop type 2 diabetes but do not have it yet. A level of 126 mg/dL or above, confirmed by repeating the test on another day, means that you have diabetes.