Fasting Blood Sugar & A1C

Q: Hello,

Thank you for addressing my question!

I have done a few home fasting glucose tests after many evenings of going to the bathroom and came out with different numbers each time. One morning it was 121, the next morning 97, another 105, and this morning 80. Here's my question, when I have my cholesterol and thyroid test done this week they will be doing an A1C. With the numbers up and down, will this one test be able to determine if I'm pre-diabetic or not? My test will be at 9:45 am after an evening fast. I know an A1C gives an average, however if there isn't any previous A1C, what do they compare this one to? I'm thinking if I'm running under 100 the day of the test, how can the test determine weather or not my sugar was elevated on the two previous occasions.

Thanks,
M.

A: M., What great questions!

Lets start with the fasting glucose readings you have done. Normal is generally 70-100. Prediabetes is occuring when fasting numbers are between 100-126. Diabetes is diagnosed when fasting numbers are above 126 on two occasions. You and your physician will talk about your fasting readings, your AIC test and together will decide about a diagnosis of prediabetes and what kind of treatment you may need. There are options of exercise, diet changes and medications.

You are right, the AIC test is an average of all your glucose readings. It is an average of the readings over the past 3 months. The results are given in a percent, with 4-6% being normal. The test is looking at how much of the red blood cells are coated with sugar or glucose. The higher the average glucose has been, the greater the percent of the red blood cell membrane is coated in glucose. In addition to the AIC percent reading, the tests are now coming with a calculated average glucose reading too. Here is an example:

Your AIC is 4.4%. That means only 4.4% of each red blood cell membrane is coated in sugar or glucose. That is a very normal amount. To find your average glucose reading with a AIC of 4.4%, we multiple the AIC by 28.7 which equals 126.28. Now we subtract 46.7 which equals 79.58, which means that over the past 3 months, your average glucose readings were 79. Each day the readings may change a little, but if there isn't a diagnosis of Diabetes, the swings are usually very small.

Please take care and be sure and discuss your test results throughly with your physician, ginny