A safe blood sugar level depends on several factors, including the type of glucose test administered and the patient's age and health, according to WebMD. Normal values differ depending on the laboratory, but the reference range used is typically listed on the lab report.
A fasting blood sugar, or FBS, test is given to patients who fast for a minimum of eight hours prior, explains WebMD. If the blood glucose is 100 milligrams per deciliter or lower on an FBS test, it is typically considered safe.
The two-hour postprandial blood sugar test is conducted two hours after the patient eats a meal. Safe levels for this test typically fall between 140 and 160 milligrams per deciliter depending on age, instructs WebMD.
A random casual test requires no advanced preparation, reports WebMD. The safe levels vary depending on the time of day the test is taken. If the test is taken first thing in the morning or before meals, a safe glucose level is generally between 80 and 120 milligrams per deciliter. If the test is taken at bedtime, a safe range is from 100 to 140 milligrams per deciliter.