There are 3 ways to diagnose diabetes

1. For people with typical symptoms of diabetes eg polyuria, polydipsia, weight loss etc, a random blood sugar > 200 is diagnostic of diabetes.

2. For people without symptoms, a fasting blood sugar of 126 and above makes the diagnosis.

3. Use standard oral glucose tolerance test to diagnose diabetes.

You need at 2 tests separated by at least 1 week to make a final diagnosis.