The 9 Worst Mistakes You Make When Checking Your Sugar

Patient Expert
Medically Reviewed
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When you use a blood glucose meter to check your level, you may sometimes get a screwy result. When that happens, you may be quick to blame your meter. But often the trouble is much closer to home.


Not washing your hands

Even if your hands don’t look dirty, when you don’t wash them before you test, you can screw up your result. Especially if you have handled fruit before testing, a study shows that your result could be way off.


Not getting enough blood

The most common mistake is not getting enough blood on the test strip. After using dozens of different blood glucose meters since a doctor told me 21 years ago that I have diabetes, I know from my own experience that when I don’t get quite enough blood on the test strip, the result the meter reports will be off.


Squeezing your finger

If your hands are cold or if circulation is poor, you may have to squeeze your finger a lot to get enough blood. When you do that, you are getting some interstitial fluid rather than blood. A study shows that this “may lead to unreliable readings." Gently warming the hands ahead of time can help so you don’t have squeeze so hard.


Using alcohol to clean your fingers

Even though some blood glucose meter manufacturers think that you should clean your fingers with alcohol, this is a mistake. The experts say that this will give you a test result that is too low.


Testing on the pad of your finger

Don’t test on the pad of any of your fingers, because you have more nerve endings there. Testing there is more likely to be painful both while you’re testing and also later when you use that finger for typing or anything else. Find out which sides of which fingers have the best blood flow. For me its the outside of my little fingers. If you test a lot, it’s a good idea to change the test site in a regular sequence.


Using test strips that are too old

Researchers from the U.S. Centers for Disease Control and Prevention found that old test strips give inaccurate readings, particularly if they are beyond their expiration date. While some meters will reject expired strips, not all of them will. And none of them will reject strips that are nearing their expiration dates, and that too, the CDC researchers told me, can give us inaccurate test results.


Missing out on important information

If your A1C level is above 8.4, your fasting level contributed the most to having a blood sugar level that is far too high. But testing two hours after the first bite of a meal can give helpful information too. This is especially important when you eat more than a few grams of carbohydrate, which is the only thing that will have much effect on your level.


Not testing enough

Few of us who have diabetes test enough. It can be helpful to test in pairs. The idea is simply to test before and after eating, before and after exercise, and before and after a stressful event.


Doing nothing with what you learn from testing

An unfortunate mistake you can make is not learning anything from your test results, as I wrote in “Don’t Waste Your Time and Money on Diabetes Testing.” Use your testing to change what you do. If your level is too high, talk to your doctor about potential changes you can make such as increasing exercise or changing your diet. Sometimes simple changes can make a big difference.