People with no diabetes have a fasting plasma glucose level under 5,6 mmol/l. After meal the glucose level doesn't exceed the amount of 7,8 mmol/l.
Diabetes mellitus exists when the fasting plasma glucose level exceeds 7,0 mmol/l or, after meal even passes 11,1 mmol/l.
A fasting value between 5,6 and 6,9 mmol/l can point out a preliminary type 2 diabetes. In this case an oral glucose tolerance test (OGTT) can bring more knowledge.