The American Diabetes Association, and doctors who treat Diabetes Mellitus, use three tests to determine if a patient is diabetic. It’s pretty simple and straightforward, and I have written about them in previous blogs! The three tests are:

1. Fasting Blood Sugar

2. Two-hour Blood Sugar (after a 75 gram oral glucose load or a large meal)

3. Hemoglobin A1C

To diagnose Diabetes Mellitus Type II, any of the following results qualify:

The Fasting Blood Sugar has to be 126 mg% or higher.

(Normal is 65 to 110)

The 2-Hour Blood Sugar has to be 200 mg% or higher.

(Normal is 140 or less)

The Hemoglobin A1C has to be 6.5% or higher.

(Normal is 4.8 to 5.7%)

These are widely-accepted diagnostic criteria used by most doctors.

Pre-diabetes is a Hemoglobin A1C between 5.7% and 6.4% or a Fasting blood sugar between 110 mg% and 126 mg%.

5% to 10% of pre-diabetics will become diabetic within one year, and 70% of them will

sometime during their lifetime.

Just like finger-stick testing of blood sugar, many doctors are recommending this method for measuring Hemoglobin A1C, rather than the long-standing practice of testing for A1C in a fasting state and performed by a certified lab. This finger-stick method is called “Point-of-care” (POC) testing.

The problem arises when you try to use POC Hemoglobin A1C testing to diagnose Diabetes. The results obtained are variable, unreliable, and not reproducible so this method for diagnosing diabetes is discouraged. Finger-stick devices for POC testing are not precise enough to prevent external factors from skewing the results. There are just too many variables that can affect the results making an accurate diagnosis uncertain.

For the ongoing management of previously-diagnosed diabetes, point-of-care testing is acceptable and recommended. The results are good enough to give the doctor a picture of the degree to which the patient’s blood sugar is under control. But when determining if a patient is diabetic, more accurate and reliable blood testing is preferred. Telling someone they are diabetic has all sorts of social and economic implications including eligibility for obtaining life and health insurance, premium rates, and disability determinations, etc. So accuracy is very important.

Using the accepted criteria for diagnosing diabetes is in the best interest of the patient. Calling someone diabetic when they’re not can be costly to them, but if they really are, treating them early and controlling their blood sugar is important for longevity, quality of life, and preventing long-term effects. Thus the need for precise and accurate results.

My recommendation for folks with a strong family history of diabetes is to have one, or all, of the above-mentioned tests every six to twelve months. It’s acceptable to have these done by the finger-stick technique for screening purposes. But if any of them is abnormal, all three tests should be repeated by a reliable lab on blood drawn from the patient’s vein. This provides the doctor with the most accurate results and thus an accurate diagnosis. This is the standard of care for diagnosing Diabetes Mellitus and should be followed by all medical practitioners.

Reference: O’Brien MJ, Sacks DB, Point-of-care Hemoglobin A1C Testing. JAMA 2019 Oct 8;322(14):1404-1405.

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