There is only one way to prove if diabetes is present: check the blood glucose. A high blood glucose is the abnormality common to all types of diabetes. There are several techniques used to measure a person's blood glucose:
FASTING GLUCOSE: The glucose content of your blood will be measured after you have fasted (not eaten) for eight hours or more. If the level is greater than 6.9 mmol/L, you will be asked to return for a repeat test. A second result above 6.9 confirms the presence of Diabetes. If the fasting glucose is very high, perhaps 8.0 or more, a second test is probably not necessary.
GLUCOSE TOLERANCE TEST: If diabetes is suspected, but can't be proven by a fasting glucose test, a Glucose Tolerance Test can be done. For this test, you are asked to go to the lab after fasting, and a blood glucose level is taken. Then you are given a sweet drink that contains 75 grams of glucose. Blood glucose is rechecked after two hours. If the blood glucose level is greater than 11.0 mmol/L, then the diagnosis is again made.
RANDOM GLUCOSE: Finally, a person with symptoms that are typical of diabetes may have a blood glucose reading taken at random, even after a meal. If the level is greater than 11, the diagnosis of diabetes can also be made.