Glucose Testing - Questions & Answers

A: Even trained lab professionals using the same lab tests can get different results. By testing you at your visits, your doctor gets a reading that can be compared with those of all the other clinic patients and with you own past and future results. Also, if your doctor’s results are quite off from yours, it may signal a problem. For example, your meter may not be working right, or your technique may have gotten sloppy.

Q: How do I know if my reading is good?

A: Glucose in your doctor’s test and in your home meter is measured in milligrams per deciliter (mg/dl). A normal reading is defined as on that falls between 70 and 100 mg/dl when someone hasn’t eaten in several hours.Just because this range is normal does not mean it’s the best goal for everyone with diabetes. When people have very high glucose level’s (greater than 200 mg/dl) their goal may be set between 110 and 140 mg/dl-- a big improvement.

Q: My doctor also has a glycated hemoglobin test. What’s that?

A: When blood glucose levels are high glucose molecules grab onto proteins and don’t let go. Glycated hemoglobin tests measure the percentage of hemoglobin molecules that have glucose molecules stuck to them. Red blood cells-the cells that contain hemoglobin-live 3 to 4 months. So the glycated hemoglobin test gives a picture of what your control has been like on average during that time.

One of the most common glycated hemoglobin tests measures glucose attached to one specific kind of hemoglobin, called hemoglobin A. You’ll often see this test abbreviated as HbA or HbA1c. In a person without diabetes, about 50% of hemoglobin molecules have glucose attached. But different labs use different methods of measuring glycated hemoglobin, and they give different results. So you’ll have to ask your doctor what your values mean.

Q: At my last doctor’s visit, I had a high glucose level, by my HbA was good. Why didn’t the results agree?

A: A blood glucose test is like a snapshot. It shows your blood glucose at one instant in time. What you’ve eaten, how active you’ve been, and when you’ve taken any diabetes drugs all can effect it. And it does not tell you what’s going on the rest of the time.

If you keep records of your results from home testing, they fill in some of the gaps. They can show the various ups and downs your glucose goes through while your awake. They can also reveal possible problems that need looking into-for example, that your glucose level stays high long after your eat pizza or that your first glucose readings on Sunday mornings is always low.But even if you tested your blood glucose 40 times per day (ouch!), you couldn’t fill in all the gaps. Here’s where the HbA can help. Because its an average, it reflects all your glucose level’s. It won’t be thrown off just because you had to run for the bus this morning. It gives a picture of your overall control.

Q: I’d like to track my long-term glucose level’s at home and not have to wait for my doctor’s visit to find out how I’m doing. Isn’t there something I can do?

A: An at-home test for glycated fructosamine was approved in December 1997. Like hemoglobin, other proteins in the blood, such as albumin, can get glucose stuck to them. "Fructosamine" is the name given to these protein-glucose combo molecules. The new fructosamine test measures the level of fructosamine in the blood.

Fructosamine has a shorter life than the hemoglobin protein. So the fructosamine test reveals average control over a shorter time: the past 2-3 weeks. Testing as often as your doctor suggests can let you know whether changes you’ve made recently are helping or hurting your glucose control. In the fructosamine test, levels less than 31 micromoles per liter (umol/l) show good control. Levels greater than 380 umol/l show poor control.

Information from the book The Commonsense Guide to Weight Loss For People With Diabetes available from the American Diabetes Association on the web at www.diabetes.org or by calling 800-ADA-ORDER.