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Checking your blood sugar levels routinely with a blood glucose meter is one of the most crucial aspects of managing diabetes. It’s the easiest way to detect and monitor trends in glucose levels, and it gives you and your physician vital information to help adjust your treatment plan and diet recommendations. To perform this valuable function, it’s important that your glucose meter displays accurate results. But how do you know if your glucose meter is accurate?
What Is an Accurate Glucose Meter Measurement?
Blood glucose meter accuracy does not mean that it will show your exact blood glucose measurement or give the same reading if you test multiple times. Instead, meter accuracy is determined by how well it corresponds with lab results that are drawn in tandem with your blood glucose meter measurement. According to the FDA, accurate glucose meters provide results that are within ±15% of the lab 95% of the time. This means if your lab test results show a blood glucose value of 170, your glucose meter reading must fall between 145 and 195 to be considered within the window of accuracy.
What Can Affect Glucose Meter Accuracy?
A number of factors can affect the accuracy of your glucose meter.
To test your glucose levels, your blood sample is placed on a test strip and converted into a glucose measurement. This process can be affected by variables such as the following:
- Damage from being bent or torn
- Exposure to excess heat or moisture
- Contaminants on the strip or test site
- Incompatibility with the glucose meter
- Being past the expiration date
Suggestion: If you’re using a meter with separate test strips, you should always follow the manufacturer’s instructions to store your test strips at an appropriate temperature in a sealed container. This helps avoid damage from heat or humidity. Always wash your hands before applying blood to the test strip to avoid contamination.
Measurements from blood samples from sites other than your fingertip may be different due to the frequency with which your blood circulates through those areas. Capillary blood taken from the fingertip will have a more current blood glucose measurement than blood taken from the arm, for example, because it can take several minutes for blood to circulate to the forearm capillaries. As a result, when testing on alternate sites it is more difficult for your meter to detect immediate effects due to recent exercise, meals, or medication, which means your blood glucose reading may be higher or lower at that moment than it would be if measured using blood from a fingertip.
Suggestion: Talk with your doctor and read your glucose meter instructions to decide which testing site is right for you and how to best assess your results.
Certain meters require you to input a code for each container of test strips so the meter can be calibrated properly before use. If the code is incorrect, your meter may produce inaccurate readings.
Suggestion: It’s important to always make sure the code on your container matches the number you input into your meter so you won’t get inaccurate glucose measurements. You may also want to consider meters that don’t require a code for calibration to avoid this entirely.
Inadequate or Excessive Blood Samples
Placing too little or too much blood on the sample area of the test strip can cause measurement errors.
Suggestion: Always read the instructions that come with your meter to identify the necessary blood sample size needed for testing. It’s also best to avoid adding more blood to a test strip after you’ve applied the initial drop.
Red Blood Cell Volume
The number of red blood cells in your blood can influence how accurate your measurements are. Because of this, medical conditions like anemia can adversely affect your glucose meter results.
Suggestion: It’s best to speak with your doctor to know if you have any medical issues that can affect your red blood cell count. If you do, it may be best to confirm that your blood glucose meter’s specifications allow testing of someone with your red blood cell count. It’s also important to avoid dehydration, which can temporarily affect red blood cell count.
How Do You Know If Your Current Glucose Meter Is Accurate?
One of the most common concerns people with diabetes have is how to know if their glucose meter is accurate.
Analyzing your device’s results against a controlled reading is the only way to evaluate the accuracy of your glucose meter. This can be done in two ways:
- Lab Tests: The most common route is to check your blood glucose levels with your glucose meter at the same time as your blood is drawn for lab glucose tests and compare your meter’s measurement with the lab results. This is the most reliable way to make sure your glucose meter’s readings fit within the 15% variability window. Be sure your meter is calibrated to read whole glucose, which is what the lab result shows.
- Control Solutions: Using a liquid control solution that has a known glucose level instead of a blood sample is another accepted way to check your glucometer’s accuracy. There is a wide array of control solutions, and most meters come with their own. You can use a control solution when you open a new test strip container, get odd glucose results, or fear you’ve damaged your glucose meter.
If for any reason your meter isn’t giving accurate measurements after testing, it’s best to either contact the manufacturer to troubleshoot the device or try a new glucose meter.
Choosing a More Accurate Glucose Meter
Accurate blood glucose measurement is a vital tool to manage diabetes and provide critical guidance for your doctor. This means it’s crucial to understand the factors that can affect your blood glucose levels—and your blood glucose meter. Although testing your blood glucose meter’s accuracy is the only way to confirm it’s up to par, choosing a glucose meter from a reputable provider can help you achieve more accurate readings. An efficient and reliable blood glucose monitor is the best way to ensure you get the results you need to assess how well your diabetes is being controlled and make adjustments that can benefit you.