COPING WITH CGM Challenges

If you’ve started using a CGM, you may have encountered a few challenges. DL diabetes educator Dr Kate Marsh discusses the highs and lows of CGM technology

- DR KATE MARSH

Following recent changes to the Australian Government’s subsidised continuous and flash glucose monitoring via the National Diabetes Service Scheme (NDSS), more Australians with diabetes are now using continuous glucose monitoring (CGM) devices. While there are many benefits to this technology – such as having access to 24/7 readings and trend arrows, the reduced need for fingerprick glucose checks, and alerts to inform the wearer of out-of-target readings – the devices are not without their problems.

ACCURACY

It can be frustrating when your CGM device and blood glucose meter show quite different readings. There are a few reasons this might happen, but the main one is what’s called lag time. CGM devices measure glucose levels in the interstitial fluid (the fluid between your cells) rather than the blood. Glucose travels to the blood first and then to the interstitial fluid, which means CGM and blood glucose levels normally won’t be exactly the same. When glucose levels are stable, the readings should be close, however, there will be a greater difference when your levels are rising or falling quickly. When rising quickly, your blood glucose reading will likely be higher than the CGM. When dropping quickly, your blood glucose reading will likely be lower than the CGM.

For devices that need calibrating, the accuracy also depends on calibrating correctly. This means following the directions from your device manufacturer as to when and how often to calibrate (each device is different), using the same blood glucose meter for all calibrations, washing your hands before a calibration fingerprick reading and only calibrating when blood glucose levels are between 2.2 and 22.2mmol/L – the devices can’t be calibrated above or below this range.