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CGM and the Trend Arrow

Continuous Glucose Monitoring is a great tool to help manage type 1 diabetes. A device that shows glucose levels 24/7 and limits the number of finger pricks you have to do definitely gets the big thumbs up from my patients! At the Family Centre, we were very excited to see the recent announcement about government-funded CGM for people with type 1 under the age of 21. If you’d like more information about applying for subsidised CGM, click here. There is much more to CGM than real-time glucose readings and rested finger tips. If you know how to use it to its full potential, CGM gives you an insight into the directions you blood glucose travels, and the speed at which it moves. The trend arrows let you see into the future, like your own personal glucose crystal ball! The Trend Arrow is a visual representation of the direction and rate at which your glucose is travelling. So what do the arrows mean, and how can you use them to improve glucose management? Direction of change – a Trend Arrow pointing up, down, or sideways Scenario 1: It’s three hours after lunch and your CGM receiver shows a glucose sensor reading of 10mmol/L. Your first thought, ‘Should I have a correction bolus? A second glance shows your trend arrow pointing down. Looks like your glucose is already heading back toward your target range! No correction needed, just a check in again a little later to make sure you’re in target. Scenario 2: It’s 7am. You wake to a sensor glucose of 4.5mmol/L. You think – might need my glucose tablets soon. However, a second glance shows the trend arrow pointing up. Looks like your glucose is safe for now, so do your usual morning thing and keep an eye on things.  Rate of change* - how many Trend Arrows are there? Scenario 3: It’s two hours after breakfast and your CGM says your glucose is 8mmol/L. Not too bad you think, I must have carb counted pretty well. Look again - multiple arrows pointing up! Your glucose has been on a fast train to high-ville for the past 20 minutes. A correction may be in order soon. Scenario 4: It's 9pm and you’re heading to bed. A final look at your CGM says 9mmol/L and you’re happy to be going to bed at this. Wait a minute… double arrows pointing down! This time that train is heading downhill. Stay awake for a little longer, have a snack on standby, and keep your eyes on the CGM screen to manage the impending crash. Bolusing with arrows Scenario 5: It's breakfast time. Your CGM shows sensor glucose is 6mmol/L, right on target. You carb count your meal and calculate your bolus insulin dose. But then you realise that 6mmol/L is accompanied by two arrows pointing down! Your calculated dose looks like it’ll be too much – a bolus adjustment is probably in order. Your own personal crystal ball So there you have it! Knowing what your sensor glucose is 24 hours a day is great. But what’s even better is knowing where it is going and how fast it is heading there. And with the new subsidised CGM, it’s a much cheaper option than having a psychic follow you around all day long. * Note: Different systems have different ways of representing rate of change – some use a directional arrow, whereas others use multiple arrows. Check the information guide for your system.

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