Diabetes can be diagnosed on the basis of plasma glucose, the criteria are fasting plasma glucose (FPG) or 2-hour plasma glucose (2-h FPG) during an oral glucose tolerance test (OGTT), or HbA1c.

Prior to the OGTT, glucose is monitored by the rapid method; if the glucose level is above 6.9 mmol/L, the glucose tolerance test is not performed and the patient is referred to an endocrinologist.