A glucose control solution is a specialized liquid containing a precisely known amount of glucose, designed for quality assurance in blood glucose monitoring. This solution verifies that a blood glucose meter and its corresponding test strips are working correctly as a system. It is a mixture of water, sugar, buffers, and microbicides, allowing it to react with the test strip’s enzyme predictably. Performing this check ensures that readings used for important health decisions, like insulin dosing, are accurate and reliable.
When a Control Check is Necessary
A control solution check maintains confidence in your blood glucose monitoring system, though it is not required for every test. You should run a control test when using a new blood glucose meter for the first time or when opening a new vial of test strips. Since the test strip enzyme is sensitive to environmental factors, this check confirms the entire batch is viable.
It is also important to test the system if you suspect physical damage to the equipment, such as if the meter has been dropped or exposed to extreme temperatures or humidity. Furthermore, if a blood glucose reading seems unusually high or low compared to how you feel, running a control check helps determine if the device is the source of the unexpected result. The primary use of the control check is to troubleshoot potential issues or verify new components.
Step-by-Step Procedure for Testing
Before beginning the control test, confirm the control solution’s expiration date and check the “discard date,” typically three months after the vial was first opened. Ensure the meter, test strip, and control solution have all been at room temperature, ideally between 68°F and 77°F, for at least 30 minutes, as temperature affects the chemical reaction. Gently swirl or invert the control solution bottle two or three times to mix the contents evenly, but never shake it vigorously, which can introduce air bubbles that interfere with the test.
Insert a test strip into the meter as you would for a regular blood test. Ensure the meter is correctly coded for the strip batch if your model requires this manual step. Some meters have a specific “control solution” or “QC” (Quality Control) mode that must be selected so the reading is not stored as a regular blood glucose result. Squeeze a small drop of control solution onto a clean, non-porous surface, such as the control solution cap, and then discard that first drop by wiping the bottle tip clean.
Dispense a second drop onto the clean surface, then touch the absorbent tip of the test strip to the solution. The solution is drawn into the strip by capillary action, and the meter will begin its countdown to display the result. Avoid applying the solution directly from the bottle nozzle to the strip, as this can contaminate the remaining solution inside the vial.
Interpreting the Results and Next Steps
Once the meter displays the result, compare this number to the acceptable range printed on the test strip vial or box insert. This range is specific to that batch of strips and the control solution level used. Control solutions often come in different levels (e.g., Level 1 or Level 2), so match your meter reading to the correct range for the specific level of solution. If the reading falls within the designated range, the system passes the quality check, confirming the meter and test strips are working accurately together.
If the result falls outside the acceptable range, the system has failed the test, and you should not rely on the meter for blood glucose readings until the issue is resolved. The first troubleshooting step is to repeat the test with a new test strip, ensuring all instructions were followed precisely and the solution is not expired. If the second test also fails, contact the meter’s manufacturer for guidance or consult with your healthcare provider. A failed control test indicates a problem with the equipment or solution itself, but it does not reflect your actual blood glucose level.
Proper Handling and Storage
Maintaining the integrity of the control solution is necessary for accurate quality checks. The solution has two expiration dates: the one printed on the bottle (for an unopened vial) and a shorter discard date that begins once the bottle is opened. Most manufacturers require the solution to be discarded 90 days after the initial opening, so write the opening date directly on the vial label.
The solution should be stored at room temperature, typically between 39°F and 86°F, and must never be allowed to freeze. Immediately after dispensing a drop, the cap must be tightly closed to prevent evaporation and contamination. Evaporation or contamination could alter the glucose concentration and cause inaccurate control test results. Once the test is complete, dispose of the used test strip following standard medical waste guidelines.