Diabetes blood Test - Fasting blood sugar and Post-prandial blood-sugar:
Fasting blood sugar
A sample of the blood is obtained when the person is in a fasting state and the amount of sugar is assessed.
This test alone is not adequate for the diagnosis of diabetes because in early or mild diabetes, the blood-sugar values may be normal in the fasting state. Thus a diagnosis of diabetes may be missed.
However' if the amount of blood-sugar in the fasting state is found to be greater than 140 mg% on two separate occasions, it is a sure indication of diabetes.
Post-Prandial blood sugar (amount of sugar in the blood after a meal or after consuming 75 gms of glucose):
A blood sample is obtained two hours after having a carbohydrate-rich meal and the amount of sugar present is determined.
According to the WHO criterion, if the amount of blood-sugar two hours after a meal is greater than 200 mg% on two separate occasions, diabetes is present. Blood-sugar values between 140 and 200 mg% should be termed 'impaired glucose tolerance'.
This is a more reliable test to diagnose diabetes than fasting blood-sugar estimation.