Slide 1. A1C: This test measures your blood sugar levels over the last 2-3 months. You don't have to fast or drink anything. Slide 2. FPG (Fasting plasma glucose): After fasting for eight hours, this test of blood sugar is taken. Slide 3. OGTT (Oral Glucose Tolerance Test): Tests how your body processes glucose two hours after drinking a special sugary drink. Random Plasma Glucose tests can be taken anytime when experiencing severe diabetic symptoms without fasting; diabetes is diagnosed at greater than or equal to 200 mg/dl.