Advances in blood glucose monitoring

Managing Diabetes Highlights:

Continuous blood glucose monitors are an alternative to painful finger pricks
New technology is able to monitor and automatically adjust insulin doses
Discover how new monitors and insulin pumps are changing the game for diabetes care

The first versions of these devices were introduced in 2014 and have been widely available in Canada since 2018. The technology uses a sensor and a reader to monitor glucose levels in the interstitial fluid.The sensor is attached to the body. A reader or a free app installed on a cell phone is used to check glucose levels. A Real-Time Continuous Glucose Monitor (rtCGM) uses Bluetooth technology to provide constant communication between the cell phone or the reader. An Intermittently-Scanned Continuous Glucose Monitor (isCGM) requires the user to swipe the reader or cell phone across the sensor. All of the devices can potentially provide glucose results 24 hours a day, seven days a week, and will store data for the past 90 days.

Not only do these devices make it easier to collect results, they also provide more valuable information. The user can tell where their glucose has been, as well as where it is going. The rtCGM and isCGM trend arrows show if glucose is going up or down quickly and needs attention, or if it is level and not a concern.

The rtCGMs and isCGMs work in pretty much the same way. A sensor, roughly the size of a toonie, is placed on the skin, usually on the arm or abdomen. A small plastic tube, about the diameter of a fishing line, is inserted from the sensor under the skin. Applying the sensor is not painful, and is easy to do. Each sensor lasts between 7 to 14 days, depending on the device.

A rtCGM usually has three parts to the system: a sensor, a transmitter, and a reader. While the sensor on a rtCGM lasts 7 to 10 days, the transmitter lasts three months. Each time a sensor is changed, the transmitter must be removed from the used sensor and applied to the new sensor.

In contrast to a rtCGM, the isCGM only has a sensor and a monitor. Once applied, the sensor can remain in place for 14 days.

Generally, the user is able to easily apply the sensor for both devices. Manufacturers include detailed, easily-followed instructions in the packaging and on their websites. Links to videos showing how to apply the sensors can be found on manufacturer websites as well as on YouTube.

The rtCGMs and isCGMs do not measure glucose in exactly the same way that a blood glucose monitor does, and so may not show the same results. A blood glucose monitor measures glucose in the blood. The rtCGM and isCGM sensors measure the glucose found in the fluid around the cells in the body. This fluid is called interstitial fluid. Glucose in the blood passes through the blood vessel walls into the interstitial fluid. The time it takes for this transfer process can cause a slight delay in the readings. However, just like cars on a subway, all are going to the same place within a few seconds or minutes of each other.