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Posts Tagged ‘Continuous Glucose Monitors’

Continuous Glucose Monitors, a Pharmacy Perspective. By Our January Student Pharmacist, Brayson Ramirez.

Checking blood sugar with finger sticks throughout the day may not be the worst part of diabetes, but it is possibly the most well-known. Finger sticks always have discomfort associated with them and nobody likes to poke themselves to draw blood, no matter how small the sample. The ability to test blood sugar without having a finger stick sounds like a dream solution to a problem affecting such a large number of people. Continuous glucose monitors, or CGMs for short, are trying to offer this option.

Image 1

Recently a new product has come to the market and has been gaining popularity in this area, but why? Continuous glucose monitors have been around for a while, but lancets and test strips have not gone away. I wanted to take this chance to look at the continuous glucose monitors from a pharmacy perspective.

There are a couple of very important variables with CGMs that are commonly not considered or well-advertised. The first is the warm-up period of the monitor system. During this time, the sensors are not guaranteed to produce accurate data, so it would not be recommended to use those readings for insulin administration or glucose record keeping.

The second variable is the calibration of the sensors as recommended by the manufacturer. In order to have the most accurate readings, calibration is required. To calibrate a sensor, a traditional finger stick reading is required. In some cases, the calibration finger sticks may be even more poking and prodding than a traditional blood glucose testing schedule.

I went through some of the more popular CGMs and made a quick summary chart of their warm-up and calibration requirements along with their life span. The products listed do not include insulin pumps that can integrate with sensors to get glucose readings.

Chart 1

As you can see from the chart, the Freestyle Libre system is the only one that does not require the user to calibrate, so it is the most likely to reduce finger sticks. All of the systems require a warm-up period. Again, the Freestyle Libre does show a bit of an improvement in this area. It has a one hour warm-up time, but it has a sensor life of 14 days, so that warm-up time will be coming around less frequently.

Image 2

When it comes to accuracy with continuous glucose monitors and traditional blood glucose meters, it is very important to understand how each works. Blood glucose meters are basically taking a snapshot of your current glucose level. CGMs measure glucose levels with interstitial glucose that is basically leaking out of your blood vessels, as seen in the above image. Since the interstitial glucose is not a direct measurement of blood glucose, the values are more like delayed blood glucose levels. With this delay, CGMs are not the best in a situation where glucose is rapidly changing, such as a severe high or low glucose reading that you are trying to recover from. In those cases, finger stick glucose readings are going to be more accurate and potentially avoid an even more serious situation.

Continuous glucose monitors have been shown to produce better outcomes overall for diabetic patients due to their more constant monitoring, but it is still necessary to keep a supply of traditional testing supplies for emergencies or sensor malfunctions.