Hello my friend Thanks for your question on HCM 1...Fasting blood sugar (FBS) For a fasting blood sugar test, do not eat or drink anything other than water for at least 8 hours before the blood sample is taken. If you have diabetes, you may be asked to wait until you have had your blood tested before taking your morning dose of insulin or diabetes medicine. 2...2-hour postprandial blood sugar For a 2-hour postprandial test, start eating a meal exactly 2 hours before the blood sample is taken. A home blood sugar test is the most common way to check 2-hour postprandial blood sugar levels. 3...Random blood sugar (RBS) and glycohemoglobin A1c No special preparation is required before having a random blood sugar or A1c test. 4...Oral glucose tolerance test For an oral glucose tolerance test, you ll need to follow a special diet for 3 days before the test. And do not eat, drink, smoke, or exercise strenuously for at least 8 hours before your first blood sample is taken. To learn more about how to prepare for this test, see Oral Glucose Tolerance Test. Hope this information is helpful Best Regards Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results may mean.