Glucose Testing

The Whys and Wherefores of Glucose Testing


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Living with diabetes without testing the blood sugar at least some of the time, is like driving a car with the eyes closed, at least some of the time.

How often should the blood sugar be tested? This depends on the person and the situation. Some patients benefit from testing the blood sugar 6 or even 10 times per day, while others get by just fine testing only 1 or 2 times per week. In general the more stable and predictable the blood sugar tends to be, the less testing is needed.

So, typically, someone who can control the blood sugar to normal without medications may need to test just as a “spot check“ a couple of times a week, while a person using an insulin pump may be testing 10 times per day. In general, anyone taking insulin will almost always benefit from testing at least 4 times per day.

In addition, more testing is always needed when there is a change in the treatment or in unusual circumstances. When you have the least time and inclination to test more, when something unusual is happening such as travel, a wedding, or an illness, that is the time to test more! If you don’t feel good and wonder if the blood sugar could be the problem, test!

When should the blood sugar be tested? It can be tested at anytime but there are 4 usual time slots per day when most testing should take place, and these are just before the main meals of breakfast, lunch, supper, and bedtime snack (or just before taking insulin for those meals). There are two reasons why these times are most useful to test, one is that knowing the blood sugar may help select the proper insulin dose and the other is that the expected range for the blood sugar is best defined at these times. We refer to this as the goal range for a patient, and typically it is 80 - 120 mg/dl, but this is not universal. We will discuss your own goal range with you and this may change over time.

We may also ask you to test one or two hours after a meal or occasionally at 3:00 in the morning. And don’t forget if you don’t feel well, you should check there and then to see if the blood sugar is the problem.

What should the blood sugar be? Some people, particularly early on in diabetes, can keep the blood sugar in the goal range most of the time. But this is unusual. Some patients taking insulin, through no fault of their own, can only achieve one quarter (1/4) of the blood sugars in the goal range, with another quarter below the goal range and the remaining half above the goal range.

It is OK to have some blood sugars below the goal range. Remember people without diabetes will normally have some blood sugars even down in the ‘60s. The lower end of the goal range is selected because we want the majority of blood sugars, but not necessarily all, to be above that number. And remember, particularly if you are taking insulin, you will have some blood sugars that are frankly low and uncomfortable. That is unavoidable. We will teach you to recognize when this is happening, to treat it properly, and to not fear low blood sugars.

Everybody with diabetes will have some high blood sugars, even when you do “everything right.” The blood sugar cannot be controlled all the time, because people are not machines. Do not get frustrated by some high blood sugars numbers, because that frustration will make the blood sugar even higher (remember, stress raises blood sugar).

How should the blood sugar be tested? There are literally dozens of meters on the market and most work quite well. We have some meters that we prefer because we can “download“ the results from them in our office. Insurance programs also have preferences and there are other reasons for selecting different meters for different people. We will make specific suggestions to you at office visits. Most of the time it is still best to check the blood sugar by “pricking“ the finger, but there are alternate site meters and new methods are emerging all the time. We will keep you up-to-date.

How accurate are the meters? In general the meters are as accurate as having the blood sugar measured in the laboratory. But the meters can break down and some meters don’t work correctly for some patients. We will work with you to ensure that you have the best meter for you. To do this we many occasionally ask you to get blood drawn in the laboratory and at that very same time in the laboratory to “prick” your finger and check your own blood sugar for comparison. All the meters that we recommend are “plasma corrected” which means that the results can be directly compared to the plasma blood sugar that the laboratory measures.

When should I call about abnormal blood sugars? You should contact us (remember there are 3 ways: fax, e-mail and phone) when you are worried by high or low numbers and don’t know what to do. Over time we will work with you so that you can manage many problems yourself. But if you are worried, get in touch. In particular we want to hear from you if you are having a lot more low or high blood sugars than is usual for you, and if you cannot figure out how to correct that problem. Diabetes is with you all the time and we are available to you all the time, not just at your scheduled diabetes visits.

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