There are two common ways that physicians assess how well diabetes is controlled - that is by way of (1) Frequent Measurements of Blood Glucose and (2) Measurement of Glycohemoglobin. Each method has its good and bad points but combined they give a fairly accurate assessment / picture of the state of glucose control in a diabetic. These methods are used by most of the physicians.
As regards measuring blood glucose levels, it can be done two different ways. Blood glucose can be measured randomly from a sample taken at any time which is called random blood sugar or RBS. Blood glucose can also be measured in the "fasting" state, meaning that the person has not eaten or taken in any calories in the past 8 hours. This is also called a "fasting blood sugar" or FBS. In a person with normal insulin production and activity, who is called a non-diabetic, blood sugar levels will return to "fasting" levels within 3 hours of eating. Diabetics (type l and type2) may not be able to get their blood glucose down this quickly after a meal or drinking a calorie-containing drink. It should be remembered that the normal fasting blood glucose level is between 70 and 110 g/dl.
As regards frequent measurement of blood glucose, the goal in this part of diabetes management is to strive to keep fasting blood sugars under 140 mg/dl and preferably closer to 70 -120 mg/dl range. Ideally, one could monitor blood sugars four times per day (or more) to follow how well the sugars are controlled. This information could be used to adjust their diet and medications to achieve this goal. Usually blood glucose measurements are done before each meal and at bedtime. Occassionally a doctor may want a diabetic patient to test their blood sugar at 2 a.m. to assess what the blood sugar is doing overnight. Generally it is desirable to have blood sugars at 2 a.m. run greater than 65 mg / dl to avoid overnight hypoglycemia (low blood sugar). It is very desirable for patients to keep a diary of those blood sugar measurements since this information will be of a great help to the attending physician as he or she makes decisions regarding how best to treat the diabetes.