The most commonly done tests to check for blood sugar are the fasting blood test and the postprandial test done after 1.5 hours of having food. When a person checks the blood for sugar, the sugar level in blood at that particular time is shown. If the fasting blood sugar reaches above 120 and the postprandial sugar is above 150, it is considered as a possibility of diabetes. But often, this value will defer according to the previous meal that was had by the person and so this cannot be taken as the criteria for prescription of medications or diet to the patient. Such inappropriate management may often lead to varied complications of the kidneys, nerves, eyes, etc. Diabetes may be a silent cause of heart diseases as well.
So, the blood sugar at a particular moment alone cannot decide the diagnosis or prognosis of a diabetic case. However, HbA1c, glycosylated hemoglobin, is the most scientific test available to find the blood sugar as it calculates the sugar level in the red blood corpuscles of the blood.
The sugar binds to the RBC of the blood. The age of one RBC is 120 days and the sugar in our blood gets deposited in the RBC in these 120 days. So, by doing this test, we can get an idea about the average sugar level over these 120 days. Thus, as compared to the blood sugar level at any given moment, the HbA1c test gives the level of sugar more accurately and can be taken as the criteria to decide medicines for diabetes.
The different ranges of this test are as follows:
HbA1c level of less than 6 mg% is a nondiabetic condition.
HbA1c above 7, needs to be brought down to below 7 by medicines or exercise.
HbA1c above 9 indicates an average sugar of the last 4 months to be above 243 mg%.
HbA1c above 8 shows sugar level of above 207 mg%.
HbA1c level of 7 or above indicates a sugar level of above 170 mg%.
HbA1c level above 6 shows the sugar level of 4 months to be 136% or above and this is why medical science considers this value as a possible diabetic case. An improvement of the diabetes is when this level is brought back to below 6.
If the level is of 6.5, it can be controlled with diet and exercise.
If the HbA1c is above 7, then medicines will be required.
If the HbA1c level stays above 7 persistently, there are possibilities of diabetic complications to the nerves (diabetic neuropathy), kidneys (diabetic nephropathy), or eyes (diabetic retinopathy).
Therefore, HbA1c must be done at least 3 times a year in a diabetic patient. If there is a possibility of diabetes, obesity, or if the diabetes is borderline, this test must be done at least twice a year.
HbA1c thus helps identify prediabetic cases and thereby diabetes can be prevented or better controlled.