A normal fasting venous plasma glucose level should be 3.9-6.1 mmol/L. If the fasting venous plasma glucose is greater than or equal to 6.1 mmol/L but less than 7 mmol/L, the patient is in prediabetes, also called abnormal glucose tolerance. People with this level of glucose need to control their diet by not eating too much sweet stuff and by eating a low-calorie diet, because if they do not control their diet, they may develop diabetes. If the fasting venous plasma glucose is greater than or equal to 7 mmol/L, the patient may have diabetes, and the diagnosis can be clarified by a follow-up fasting venous plasma glucose test at the hospital every other day.