Prediabetes is the precursor stage before diabetes mellitus.

Prediabetes is the precursor stage before diabetes mellitus in which not all of the symptoms required to diagnose diabetes are present, but blood sugar is abnormally high. This stage is often referred to as the "grey area." It is not a disease; the American Diabetes Association says, "Prediabetes should not be viewed as a clinical entity in its own right but rather as an increased risk for diabetes and cardiovascular disease (CVD). Prediabetes is associated with obesity (especially abdominal or visceral obesity), dyslipidemia with high triglycerides and/or low HDL cholesterol, and hypertension." It is thus a metabolic diathesis or syndrome, and it usually involves no symptoms and only high blood sugar as the sole sign. Impaired fasting blood sugar and impaired glucose tolerance are two forms of prediabetes that are similar in clinical definition (glucose levels too high for their context) but are physiologically distinct. Insulin resistance, the insulin resistance syndrome (metabolic syndrome or syndrome X), and prediabetes are closely related to one another and have overlapping aspects.