Sometimes my blood glucose monitor seems to give incorrect readings. What can I do to make sure the measurement is accurate?
Blood glucose monitors are small devices that measure and display blood sugar levels. They measure glucose in blood in the smallest blood vessels, called capillaries, in the finger or other sites. They're useful tools for managing diabetes.
The readings most often are true when you use the monitor right. But sometimes, monitors may give glucose readings that are not the same as the glucose measured in blood drawn from your arm.
This may be because there are times when glucose changes quickly, such as after eating. Then the numbers can differ greatly between the two types of tests. The monitor reading when you haven't eaten should be within 15% of the fasting glucose test reading.
Here are some things that affect how well your blood glucose monitor works and how to fix or prevent wrong readings:
| Factors that affect accuracy | Solutions |
|---|---|
| Test strip issues | Throw out damaged or outdated test strips. Store strips in their sealed container; keep them in a dry place. Be sure you have the right strips for your glucose monitor. |
| Temperature | Keep your glucose monitor and test strips in a dry place at room temperature. |
| Alcohol, dirt or other matter on your skin | Wash and dry your hands and the testing site well with soap and water before pricking your skin. Don't use hand sanitizer before testing. If using alcohol wipes, let the site dry all the way before you prick your skin. |
| Monitor issues | Put the test strip all the way into the monitor. Make sure monitor batteries are charged. Change the batteries as needed. Get a new monitor every 4 to 5 years. |
| Not enough blood on the test strip | Newer monitors give you an error reading if there's not enough blood. Don't add more blood to the test strip. Use a new strip. |
| Testing site | If you use a testing site other than your fingertip and you think the reading is wrong, test again with blood from a fingertip. Blood samples from other sites aren't as true as fingertip samples when your blood sugar level is rising or falling quickly. |
| The amount of red blood cells in your blood | Your test results may be less true if you've lost too much fluid, called dehydration, or if you have a low red blood cell count, called anemia. |
| Medicines | Certain medicines can affect glucose readings. They include acetaminophen (Tylenol, others) and high doses of vitamin C. Also, having too much uric acid in the body can affect readings. |
- Ways to test your blood glucose monitor
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The following tests can let you know that your monitor is working as it should:
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Test using a control solution. Follow the steps for a blood test using a liquid control solution instead of blood. These solutions often come with your monitor. And you can get them at drugstores and pharmacies. Follow package directions.
Use liquid control solutions every time you open a new container of test strips. Then use the solutions now and then as you use the strips. Also use liquid control solutions if you drop your blood glucose monitor and when you get results that don't seem right.
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Match your reading with lab results. Take the blood glucose monitor with you when you visit your healthcare professional or go to a lab for fasting blood tests for glucose. Check your blood sugar level with your monitor when you have blood drawn for lab tests. Use a fingerstick sample, not blood from the blood draw.
Compare your monitor's reading with the lab fasting glucose results. You want results that are within 15% of the lab reading.
If your monitor doesn't work right, contact the company that makes your monitor and test strips.
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