Checking your blood glucose monitoring system to make sure it is working properly can be done easily at home with a glucose control solution.
Control solution can also be handy to practice using your meter without needing to do a finger stick. Testing using a control solution is a similar process to testing a blood sample.
However, the properties of the fluids are different, and the test results are used for separate purposes.
Control solution for a glucometer has a known amount of glucose set by the manufacturer, whereas the concentration of glucose within human blood can fluctuate, even when measuring the same drop of blood.
Therefore, a control solution test can be used to check if your meter and test strips are reading blood sugar levels properly by providing the expected result.
Glucose control solution is a liquid made up of water, glucose, buffers, and microbicides. These ingredients are vital to creating a solution with the following properties:
• Has a concentration of glucose that can be used to test the functionality of your meter and test strips.
• Has a pH level that is close to the physiological value of human blood.
• Prevents the growth of micro bacteria that would otherwise alter the glucose concentration.
Your blood glucose monitoring system can detect the amount of glucose present in the control solution in a similar way to how it detects the amount of glucose present in blood.
A glucose control solution reading on your meter appears as a numerical value. This value should fall within the target range printed on the test strip vial, which is based on the concentration of glucose in the control solution.
Manufacturers often have a few options of control solution that are compatible with each brand of test strips. The different options, or “levels” — Level 1, Level 2, or Level 4 for example — have glucose ranges that are different from one another, typically corresponding with low, normal, or high glucose concentrations.
Your test strip vial should show the target range for each different level of control solution. Be sure to identify the correct range that corresponds to the type of control solution you have.
Glucose control solution can be used to complete a quality check on your blood glucose monitoring system. It can help you determine if your meter and test strips are performing properly.
How often is a glucose control solution test recommended?
Control solution tests may need to be performed numerous times throughout the lifetime of a meter for a variety of reasons.
A control solution test is recommended when:
• You suspect that your meter or test strips are not working properly.
• You suspect your test results are unexpectedly too high or low, or do not match how you’re feeling.
• Your test strip vial is damaged or was not capped tightly.
• You have dropped or damaged your meter or exposed your meter to liquids.
• Your meter or test strips have been exposed to extreme environmental conditions, like humidity,
• Temperature, or sunlight.
• You are advised by a healthcare professional to do so.
Regardless of the reason for a glucose control solution test, the purpose is always the same: to determine whether your meter and test strips are performing as expected by the manufacturer. However, this does not indicate how accurate your glucose meter is.
How to check the accuracy of a glucose meter?
While it is tempting to use the results of a control solution test to find out if your meter is reading high or low and by how much, the properties that make blood and control solution different prevent this from being a reliable way to check the accuracy of a glucose meter.
Instead, it gives you an indication as to whether your meter and test strips are working properly. Once a control solution test confirms that your monitoring system is functioning correctly, accuracy of blood glucose meter readings can be affected by many factors unrelated to the meter’s functionality, such as environmental conditions, altitude, testing practices, and damaged or expired test strips.
Something as simple as testing with unwashed hands or from an insufficient blood drop can throw off your entire test. Therefore, identifying and controlling any interfering factors can be a simple step to improving the accuracy of your results.
If you are still wondering how to check the accuracy of a glucose meter, the Diabetes Technology Society completed a study that evaluated the accuracy performance of popular meters on the market.
It is important to remember that this study evaluated meters using a controlled method and that comparing test results from two different meters is not recommended due to the variances in meter technology from one brand to another.
Also, factors like the ones mentioned above can influence accuracy to yield different results from one test to the next.
How to perform a control solution test?
Glucose control solution tests are performed the same way as blood glucose tests. These tests are not a method for calibrating your meter, but rather a useful tool to check the performance of your meter and test strips.
You can also use a control solution to practice testing with your blood glucose monitoring system before testing a blood sample.
Here are the steps to guide you through the process:
Step 1: Insert a new test strip into your meter and check that the meter is ready to perform a test.
Step 2: Shake the control solution bottle vigorously.
Step 3: Discard the first drop and wipe off the bottle tip so that it is clean.
Step 4: Dispense a second drop onto a hard, clean surface, then bring the test strip to the drop. Hold the test strip up to the sample until enough control solution has been applied to the test strip.
Step 5: Check the meter as it calculates and displays the test result. Compare the test result to the appropriate control solution range printed on the test strip vial.
Step 6: Dispose of any used test strips and store the control solution bottle with your testing supplies.
How will I know if the control solution test passed?
Once you have the result from the glucose control solution test, the next step is to compare the number shown on your meter to the range specified by the manufacturer, printed on the test strip vial. The number shown on the meter should fall within the range. It is important to remember that results from control solution tests are unrelated to blood glucose levels and do not reflect your body’s blood glucose concentration.
A range for control solution results — rather than a single number — is provided because no two tests will be exactly the same. Manufacturers anticipate the possible variations from test to test and therefore provide an expected range.
If you find that a control solution result does not fall within the range printed on the test strip vial, you should contact the manufacturer of your meter to determine if additional troubleshooting or replacement supplies are needed.
How long does the control solution last?
Most control solutions for glucose meters last 90 days from the date that the bottle is first opened.
However, some manufacturers make their control solution to last longer. It is always best to use a control solution before the expiration date on the box, and to discard the bottle after it has been opened for the time period specified by the manufacturer.
After each use, be sure to re-cap the control solution bottle, forming a tight seal. Temperature and humidity can affect the control solution and potentially alter the result of a control solution test.
Therefore, check the storage conditions on the bottle to determine the best place to store it.
Where to buy control solution for a glucose meter?
Typically, a control solution for a glucometer is available from the manufacturer of your meter and test strips.
Check the manufacturer’s website for details on where to purchase control solutions. You can also check with your local pharmacy to see if they have available stock of the control solution that is compatible with your glucose meter. If none is in stock, you can request it to be ordered through your pharmacy.
Can any kind of glucose control solution be used?
Control solution for glucose meters is made specific to each brand and type of test strip; there is no universal or generic brand. If you are unsure which control solution is designated to work with your glucose monitoring system, check the instructions that came with your meter or test strips or look on the manufacturer’s website.
Checking your blood glucose Checking your blood glucose monitoring system using a control solution is important anytime you or your doctor believes there could be damage to your meter or test strips, or concerns about the performance of your system.
While a control solution test cannot provide insights into the accuracy of your meter, it is a helpful method to determine if your system is working properly.
This test can be done in a few simple steps, at home.
The author is a Microbiologist and a Certified Infection Control Auditor at Kidney Hospital Srinagar.
Disclaimer: The views and opinions expressed in this article are the personal opinions of the author.
The facts, analysis, assumptions and perspective appearing in the article do not reflect the views of GK.