To Your Good Health
DEAR DR. ROACH: I’m confused by the relationship between my blood glucose level and A1C. My blood glucose has crept up from 100 to 112 in one year after I started taking 40 mg of atorvastatin. My A1C level is 5.1%, apparently “normal,” so my doctor is unconcerned about the blood glucose reading.
When is it time to become concerned? When my blood glucose goes up another 15 points and brands me as diabetic? Does A1C “trump” blood glucose results to the degree that the blood glucose test can be disregarded? If so, why even bother to test blood glucose? — J.S.
ANSWER: Diabetes can be diagnosed by blood sugars, which are a “snapshot” of blood sugar in time; by an A1C test, which looks at blood sugar averages over the last few months; or by a glucose tolerance test, which is a stress test on your pancreas’ ability to make insulin in response to a sugar load.
The A1C is most commonly used and is also used to monitor blood sugar in people with diabetes. A level of 5.1% is normal, between 5.7% and 6.4% is considered prediabetes, and 6.5% and higher is considered diabetes.
People can have diabetes with a normal A1C, and even with normal fasting blood sugars. The glucose tolerance test is the most sensitive test for most people, since high blood sugar after eating usually happens long before high fasting sugars.
Blood sugar may be high for only a short period, so the A1C can be near normal. However, it would be very unusual to see an A1C of 5.1% in a person newly diagnosed with diabetes. It could happen if the change in blood sugar is very recent.
I hope your doctor really is concerned, even if they aren’t showing it. Atorvastatin can increase blood sugar, although not usually enough to make someone cross over into diabetes territory. The few times I order a glucose tolerance test are in cases like yours, where the blood sugars are at odds with the A1C level.
EDITOR’S NOTE: Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.