Diabetes mellitus is characterized by recurrent or persistent high blood sugar, and is diagnosed by demonstrating any one of the following: -

Fasting plasma glucose level ≥ (126 mg/dl)

Plasma glucose ≥ (200 mg/dl) two hours after a 75-gram oral glucose load as in a glucose tolerance test (OGTT)

Symptoms of high blood sugar and casual plasma glucose ≥ (200 mg/dl)