This is the question my diabetic patients always ask. There are various methods to determine blood sugar level. Some tests give you accurate diagnosis of diabetes or pre-diabetes, while others will tell you how well you are managing your diabetes.
Fasting Blood Sugar Test:
Measures the gulucose level after 8 hours fast or overnight. Normal fasting glucose is less than 100mg/dl. If your fasting glucose is from 100mg/dl to 125mg/dl then you will have impaired blood glucose also known as Pre-Diabetes. If your sugar level is above 125mg/dl then your doctor will diagnose as a patient of diabetes. To confirm the diagnosis, your doctor may repeat the fasting blood glucose test on any other day. If you have blood sugar level of 126mg/dl or higher in two consecutive tests, then you may have diabetes. If you have glucose greater than 200mg/dl and you have symptoms of diabetes like increased thirst or hunger, frequent urination, weight loss, blurred vision etc, then you may be diagnosed with diabetes mellitus without confirming it with second test.
Random Blood Glucose Test:
Random blood sugar test gives your blood sugar at any time in a day. Normal random blood sugar level should be less than 200mg/dl. If your random blood sugar is between 140mg/dl to 200mg/dl then you will have pre-diabetes.
Oral glucose tolerance test
This test measures your response to sugar. First we measure fasting glucose, and then glucose solution is given, after that we measure blood glucose after 1 hour and 2hours. A normal blood glucose level after an oral glucose tolerance test is less than 140 mg/dL. Level between 140 mg/dL to 199 mg/dL suggests pre-diabetes. A glucose level of 200 mg/dL or higher two hours after you drink the glucose solution may suggest that you have diabetes mellitus.
Glycated hemoglobin (A1C) test
This test is not for diagnosing diabetes, but it shows you how well you have controlled your sugar in last 2 or 3 months. Normal value is less than 7%, however if it is more than 7 then you and your doctor should think of changing your treatment of diabetes.
Always Remember, your blood glucose measurement alone is not enough to differentiate between type 1 and type 2 diabetes. Your doctor may do some other tests to find out which type of diabetes you have.