The term borderline diabetes has now been replaced by the term prediabetes. Both terms indicate that a person has abnormalities in his or her plasma glucose levels that fall short of standard accepted definitions for frank diabetes. The normal ranges for both fasting plasma glucose and for plasma glucose after a glucose load by mouth. The reason that a standardized 75 gram (a little under 3 ounces) glucose load is used is to allow a direct comparison between different individuals under the same conditions.
The table also shows the glucose levels above which diabetes is diagnosed. The range between the upper end of normal and diabetes itself is the prediabetic range. For fasting glucose, the range is 100 to 125 mg/dl and for glucose values 2 hours after a standard 75 gram glucose drink by mouth, it is 140 to 199 mg/dl. The former is termed impaired fasting glucose, or IFG, and the latter is termed impaired glucose tolerance, or IGT. When either is present, an individual is described as having prediabetes.
There are at least two reasons why it is important to identify prediabetes. One reason is that people with prediabetes have a known increased risk of progression to frank type 2 diabetes and, second, prediabetes, especially of the IGT type, is associated with a significantly higher risk of cardiovascular disease and death. Therefore, knowledge that one has prediabetes necessitates regular follow-up and also permits early intervention to prevent progression to frank diabetes.