Before people develop type 2 diabetes, they almost always have "pre-diabetes" - blood-glucose levels that are higher than normal but not yet high enough to be diagnosed as diabetes.
Two different tests are used to find out whether you have pre-diabetes: a) the fasting plasma glucose test and, b) the oral glucose tolerance test.
The blood-glucose levels revealed in these tests show whether your metabolism is functioning normally, or whether you have diabetes or pre-diabetes.
A person with pre-diabetes has a fasting blood glucose level between 110 and 125 mg/dl. Anything over this indicates the onset of diabetes.
The oral glucose tolerance test measures a person’s blood glucose level after a fast and 2 hours after drinking a glucose-rich beverage. If you're prediabetic, your blood-glucose level will be between 140 and 199 mg/dl. Anything over this indicates the onset of diabetes.
If you're overweight and older than 45, you should be tested for this condition. In fact, anyone with a family history of diabetes, anyone who has high cholesterol, anyone who had gestational diabetes, who is overweight or who belongs to an ethnic group where diabetes is a problem, should consider regular testing for this condition. Even very obese children and teenagers have been found to be pre-diabetic.
Remember that it's quite possible to be pre-diabetic or diabetic and be unaware of it, as the onset of the symptoms is usually gradual. The symptoms include frequent urination, excessive thirst, increased appetite, weight loss, blurred vision and exhaustion.