What is Continuous Glucose Monitoring (CGM)?
While blood glucose checking measures the Blood Glucose Level (BGL) via a drop of blood on a test strip, CGM works by a sensor measuring the glucose in the fluid around the cells under the skin (this is called interstitial fluid). The sensor is inserted under the skin. A transmitter connects to the sensor and sends the sensor glucose reading to a device (a phone, insulin pump or a Libre glucose meter). These are called Sensor Glucose (SG) readings
When glucose levels are stable and the system is correctly calibrated (if needed), the BGL and the SG are likely to show similar readings. When glucose levels are changing quickly (such as after giving insulin, eating, exercise or hypo treatment, or when you are unwell etc.) you should expect differences between the two readings. It takes time for the glucose to move from the blood stream into the interstital fluid area.
CGM systems currently available (for injection users)
Dexcom G6 CGM
Dexcom G7
Dexcom G7 will be available in September 2024 to purchase on the AMSL website. NDSS have not released any details about a subsidy for the Dexcom G7 yet.
The Dexcom G7 has the same 10 day sensor wear with the cost of $110 per sensor or $330 per month. The Dexcom G6 continues to be available.
Libre 2 CGM
Medtronic Guardian 4 Smart CGM
Image from NDSS website. Further information is availble from NDSS . Please click here
Dexcom Overpatch
Dexcom Sensor Overpatches for use with Dexcom G6 Continuous Glucose Monitoring (CGM) Sensors may help in keeping your sensor adhesive secure and clean. They are available at no charge if using a Dexcom sensor product - order here
Some limitations of CGM
It is important to understand that these systems are used in addition to, but do not completely replace BGL checking using finger pricks. Please read the “fine print” when companies write “no more finger pricks” or similar and privacy statement for access to technology
BGLs are checked:
- To confirm the blood glucose when symptoms do not match the SG reading
- When the sensor glucose is less than 4 mmol/L to confirm hypoglycaemia before treatment
- After hypoglycaemia treatment to confirm blood glucose has risen above 4 mmol/L
- When insulin is due and the sensor glucose reading is above 15 mmol/L
- During “warm up” of the device. During warm up SG readings are not available
- When the device disconnects or fails to give readings
- To calibrate the sensor (if required by your chosen device)
When using CGM a receiving device is required. If parents want to follow and receive real time information, the receiving device will need access to wifi or have a data plan. NDSS funding for CGM is limited to the CGM, not the receiving devices or data plans.
Some benefits of CGM
- The trend graphs show glucose readings between blood glucose checks. Trend graphs can be used to interpret the effects on blood glucose of different foods and exercise. It also shows 24 hours of glucose trace, including overnight. Some parents find this reassuring
- CGM can be set to alert if the SG reading is above or below set glucose values
- Trend arrows indicate the rate of change in the SG reading. This can be particularly helpful during exercise or exams or while driving as it can prompt a blood glucose check. The glucose trend can also reassure parents when the glucose is in target and stable that extra carbohydrate is not required, reducing eating those extra carbs "just in case" a hypo occurs
- All companies have interactive reporting available showing insulin doses, carbohydrate eaten and exercise markers, however this information must be entered in by the user. The reports also show the trends in SG readings over different days, the time glucose has been within range and patterns in above or below target readings. This can be very helpful in reviewing insulin doses and carbohydrate intake.