A normal blood glucose level is less than 6.1 mmol/L, when measured after a fast. In general, a normal glucose would be less than 7.8 mmol/L if taken about 2 hours after eating. Within 3 hours of eating, the glucose should be under 6.1 again.
The glucose levels we aim for and consider good control of diabetes may be a little looser than this. Fasting glucose (or glucose before other meals) less than 7 mmol/L is usually considered good glucose control. If testing 2 hours after eating, we would generally recommend levels less than 10 (less than 9 would be even better).
The above values are based on glucose levels associated with complications of diabetes, particularly eye and kidney disease. It's quite possible that we should be aiming for much lower glucose values to reduce the risk of heart disease, perhaps less than 5 before meals, and less than 6 after meals. This may however be practically impossible with our present medications, the limiting factor being low blood sugars (hypoglycemia).