Monitoring blood glucose at home is second nature to many people with diabetes. In fact, it’s often so automatic that you may not stop to think about all the steps in the process that may interfere with achieving an accurate blood glucose reading. First, there’s the near-automatic loss of accuracy that comes from taking a blood sample from capillaries, which is what happens with both fingertip and alternate-site testing. The blood glucose level in your capillaries is delayed compared to the blood glucose level in your veins, which is considered your “true” blood glucose level and is what lab tests measure. The two levels may differ by as much as 10% to 15%, depending on how quickly your blood glucose level is changing. If you’ve been fasting and your blood glucose level is stable, the two probably won’t differ by very much.
Second, your blood may become tainted when it reaches the surface of your skin, especially if you’ve been handling food prior to lancing your finger. And third, the test strip or meter you use may deliver inconsistent or inaccurate results. This last possibility is one that people with diabetes often forget about. After all, meters give the impression that they can pinpoint the exact glucose level of blood samples; they don’t display a range of possibilities. But most new meters are only guaranteed to be accurate within a 20% range. This means that if your actual blood glucose level is 100 mg/dL, the meter might display a number anywhere between 80 and 120. And malfunctioning meters can, of course, be even less accurate. So how can you know if your meter is misbehaving? This is where control solution comes in.
Control solution is essentially “fake blood” that contains a known level of glucose. It is applied to a test strip just like a normal blood sample, and the resulting reading lets you know how well that test strip and your meter are working. But as a recent survey shows, many people with diabetes don’t use control solution, and many doctors don’t recommend it. Conducted by researchers at the University of Oklahoma at Tulsa, the small survey asked doctors, patients, and pharmacists in the area a range of questions related to control solution. According to an article on the survey at MedPage Today, only 23% of people with diabetes who were surveyed said they used control solution as part of their monitoring routine. While 56% of doctors said they recommended using it to their patients, only 14% of pharmacists said they consistently recommended it to people who bought other blood-glucose-testing supplies.
The researchers found that out of 25 pharmacies in the Tulsa area, only one had control solution displayed in an area where patients could see it. All pharmacists surveyed said they were familiar with control solution, and 61% said they believed it should be a routine part of blood glucose management. Yet only 39% said they regularly stocked control solution, and 43% said they never actually recommended it to patients; 43% also said they sometimes recommended it. Out of the people with diabetes who were surveyed, 67% said they didn’t use control solution because they didn’t know about it. Of the doctors who were surveyed, 38% indicated that they were not familiar with control solution, and some others said they didn’t think it was needed with newer meters.
So should everyone with diabetes use control solution? Not all experts think so. Wil Dubois, a diabetes author who has written for Diabetes Self-Management, opined last year in a post at Diabetes Mine that control solution seems like a ploy to get people with diabetes to use even more test strips. That’s because the solution is only as useful as it, itself, is accurate. Most control solutions aren’t guaranteed to contain an exact concentration of glucose in every sample; just like meters, they have a listed range of accuracy. So if a control solution has a range of, say, 95–125 mg/dL, then your meter may display a reading of anywhere from 76 to 150 mg/dL and still fall within the meter’s 20% range of accuracy.
What’s your experience with control solution — has your doctor or another member of your health-care team recommended that you use it? If so, how often do you use it? Have you found it to be useful in spotting test strip or meter errors, or has it just confirmed that none of your equipment is malfunctioning drastically? Would you use control solution to check your meter if the solution could be guaranteed to contain an exact glucose level? Has control solution given you more confidence in your meter’s readings? Leave a comment below!