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. There are 57 million people in the United States who have pre-diabetes. Recent research has shown that some long-term damage to the body, especially the heart and circulatory system, may already be occurring during pre-diabetes. There are two different tests your doctor can use to determine whether you have pre-diabetes: the fasting plasma glucose test (FPG) or the oral glucose tolerance test (OGTT).
The blood glucose levels measured after these tests determine whether you have a normal metabolism, or whether you have pre-diabetes or diabetes. If your blood glucose level is abnormal following the FPG, you have impaired fasting glucose (IFG); if your blood glucose level is abnormal following the OGTT, you have impaired glucose tolerance (IGT).
It is important to diagnose prediabetes early, so that diabetes prevention measures can start as early as possible.