Diabetes Forecast

Continuous Glucose Monitors 2014

Is the trend your friend? A CGM tracks blood glucose ups and downs

By Tracey Neithercott , ,

A finger-prick blood glucose check gives you only one number in time. It’s hard to know: Is your blood glucose rising, falling, or staying steady? A continuous glucose monitor (CGM), however, records hundreds of readings a day.

A CGM consists of three parts: a small under-the-skin sensor that measures glucose levels in what is known as interstitial fluid; a transmitter that attaches to the sensor and transfers data; and a receiver that displays glucose information and stores data. The sensor measures glucose every five minutes or so.

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While CGM glucose readings are somewhat less accurate than finger-stick glucose readings, they can give you a good idea of where your glucose is trending. Say, for instance, your meter reads your glucose as 130 mg/dl. A CGM may report a similar number, but it can also tell you in what direction your glucose is headed—and how fast. Plus, you can set thresholds for high and low numbers, and the CGM will alarm to alert you once it senses your glucose level has risen above or fallen below the safe range you set. CGMs also sound an alarm if the rate of increase or decrease is very fast.

Some people find the alarms a lifesaver—especially if they have hypoglycemia unawareness, the inability to sense their lows. Some people still manage to sleep through the alarms. And some people dislike the frequency of false alarms and having an audible reminder of their fluctuating blood glucose levels.

Most CGMs on the market offer the same functions—all display arrows to indicate the direction your glucose is trending, for instance. But there are certain aspects that differ.

Sensor duration: Sensors range from three to seven days’ approved wear, depending on the brand. Wearing a CGM sensor past its recommended duration can irritate the skin at the insertion site. And toward the end of a sensor’s life span, the adhesive that sticks the sensor and transmitter to your skin may begin to peel.

Range: A CGM transmitter will wirelessly relay data from your sensor to your receiver, but stray too far from the receiver and you’ll lose the connection. If you plan to separate your sensor and receiver—say, if you’re a parent checking your child’s glucose data when he or she isn’t sitting next to you—be sure to note the sensor range.

Meter interaction: You don’t kiss a meter goodbye when you get a CGM, but you may use far fewer test strips. Blood glucose tests—two daily—are necessary to regularly calibrate a CGM. A CGM may allow for wireless transfers between a companion meter, might use a connection cable to upload data from a specific meter, or may rely on your manually entering the meter result in the CGM.

Pump interaction: Two of the available CGMs function as combination insulin pumps and continuous glucose monitors. All data are displayed on a single device that controls both pump and CGM functions.

Pediatric use: Not all CGMs are approved for use in children. Parents will want to ensure the device they choose has been approved for pediatric use.

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