Welcome to The Glucose Neverlies Podcast and our special CGM Series, where we take a deep dive into CGM systems and how to optimise their use for better diabetes management. Whether you are new to CGM or looking to fine-tune your approach, this series will provide the 101 on how to assess CGM accuracy. Then we get into the fun stuff, the unique function’s of the different CGM systems.
Across three episodes, we’ll explore CGM accuracy and the regulatory landscape. For the most accurate CGM systems, we’ll highlight their unique strengths and the best ways to get the most out of them. You can dive deeper into all the details in the CGM Systems Guide.
Episode 10: CGM Accuracy (Part 1) – Study Design First, Performance After
In this episode of the Glucose Never Lies podcast, hosts John Pemberton and Louise Collins delve into the intricacies of diabetes management, focusing on continuous glucose monitoring (CGM) systems. They discuss the importance of understanding CGM accuracy, the significance of study design in evaluating sensor performance, and the key questions to ask when assessing the reliability of these devices. The conversation emphasises the need for robust testing conditions to ensure that CGMs provide accurate readings for insulin dosing decisions. The hosts also highlight the ongoing efforts towards standardisation in CGM technology to improve diabetes care.
This chart is an early prototype of a chart developed in collaboration with the DSN Forum (Beth, Amanda, and Tamsin are great fun!) to help the community understand study design before considering performance. An updated version will be published soon, and I’ll share the link once it’s available.
Takeaways
- Continuous glucose monitors (CGMs) are crucial for insulin dosing decisions.
- Understanding study design is essential for evaluating CGM accuracy.
- Not all CGMs are created equal; performance varies significantly.
- Key questions to assess CGM accuracy include the study population and testing conditions.
- Robust testing conditions are necessary for reliable sensor performance.
- The importance of peer-reviewed data in evaluating CGM accuracy.
- Standardization in CGM technology is on the horizon.
- Healthcare professionals should be knowledgeable about CGM performance.
- A downloadable chart will be available to help users assess CGM options.
Chapters
00:00
Introduction to Diabetes Management
02:14
Understanding Continuous Glucose Monitoring (CGM)
05:11
Accuracy of Continuous Glucose Monitors
10:13
Evaluating Sensor Performance
15:45
Key Questions for Sensor Accuracy
20:31
Moving Towards Standardization in CGM
25:03
Summary and Next Steps
Key Resources
- Understanding Risk Before Performance
- Show Notes and Transcriptions
- Chart for CGM Devices (From May 2025): DSN Forum
- Tim Street @ Diabettech
Episode 11: CGM Accuracy (Part 2): Understanding MARD, 20/20, 40/40, and Error Grids.
In this episode of the Glucose Never Lies podcast, hosts John Pemberton and Louise Collins discuss the intricacies of diabetes management, focusing on continuous glucose monitoring (CGM) systems. They explore the importance of CGM accuracy, the standards set by regulatory bodies, and the significance of testing conditions in evaluating these devices. The conversation delves into various metrics used to assess CGM performance, including Mean Average Relative Difference (MARD), 20/20, and 40/40 agreement rates (see table below), and highlights the need for robust testing against capillary glucose to ensure effective diabetes management. The episode emphasises the importance of transparency in CGM studies and the future directions for standardizing testing protocols.
Takeaways
- CGM systems are crucial for real-time glucose monitoring.
- FDA standards are currently the highest for CGM performance.
- CE marking does not guarantee device accuracy or reliability.
- Testing conditions significantly impact CGM accuracy results.
- The 20/20 standard indicates no risk for insulin dosing decisions.
- The 40/40 metric identifies high-risk readings in CGM data.
- Robust testing against capillary glucose is essential for accuracy.
- Standardization in CGM testing is needed for better diabetes management.
- Transparency in CGM studies is vital for healthcare professionals and patients.
Chapters
00:00
Introduction to Diabetes Management and Podcast Goals
02:07
Understanding Continuous Glucose Monitoring (CGM) Systems
06:08
Evaluating CGM Accuracy and Performance Standards
10:09
The Importance of Testing Conditions in CGM Studies
14:13
Metrics for Assessing CGM Accuracy
18:03
Comparing CGM Systems Against Capillary Glucose – This picture highlights how the Medtronic Simplera massively underreports post-meal glucose exposure because it aligns closely with venous glucose values rather than capillary. In contrast, both the Dexcom G7 and FreeStyle Libre 3 track much more closely to capillary glucose, which more accurately reflects what the human body is actually exposed to (the study).
Under the principle of “what gets measured gets managed,” this means high glucose levels are likely to be managed more effectively with the Dexcom G7 or FreeStyle Libre 3 than with the Simplera.
This also underscores the urgent need for the IFCC’s ISO to be with us as soon as possible.
The consequence?
The Medtronic Simplera overestimates time in range (3.9–10.0 mmol/L or 70–180 mg/dL) and underestimates time above range (>10.0 mmol/L or 180 mg/dL). This can give users the false impression that their glucose control is excellent—they think they’re doing great, only to be surprised when their HbA1c results come back higher than expected.
The reality is that their body has been exposed to higher glucose levels than the Simplera had indicated. On the other hand, users of the Dexcom G7 and FreeStyle Libre 3 receive a more accurate reflection of capillary glucose levels, giving them a clearer understanding of their true glucose exposure—and with it, a better sense of their future complication risk. – See the study.
22:02
Future Directions for CGM Testing and Standards
Key Resources
- CGM Series: Assessing CGM Accuracy Performance
- Show Notes and Transcription
- Chart for CGM Devices (From May 2025): DSN Forum
- Tim Street @ Diabettech
Episode 12: CGM Functionality (Part 3): The Bells and Whistles
In this episode of the Glucose Never Lies podcast, hosts John Pemberton and Louise Collins discuss the intricacies of diabetes management, focusing on continuous glucose monitoring (CGM) systems. They explore various CGM features, including calibration, alarms, and connectivity with automated insulin delivery (AID) systems. The conversation emphasizes the importance of understanding individual needs when selecting a CGM, as well as the role of technology in enhancing diabetes care. The hosts also provide insights into the latest advancements in CGM technology and offer resources for further education
This summary table is from the detailed CGM Systems Guide and helps match the right system to the right priorities. There’s no one-size-fits-all—just like Zara Larsson says, you love who you love!
Takeaways
- Continuous glucose monitors (CGMs) have evolved to include factory calibration.
- Optional calibration can be beneficial, but requires accurate blood glucose meters.
- Alarm fatigue can hinder effective diabetes management.
- The Freestyle Libre is noted for its small size and long wear time.
- Dexcom products offer extensive connectivity with AID systems.
- Understanding individual needs is crucial when selecting a CGM.
- AI-driven forecasts in CGMs can enhance decision-making for users.
- Education and support are vital for effective diabetes management.
- Resources like the DSM Forum provide valuable information for diabetes care.
Chapters
00:00
Introduction to Diabetes Management
02:14
Continuous Glucose Monitoring (CGM) Overview
13:09
Understanding CGM Features and Alarms
21:27
Evaluating CGM Size and Connectivity
27:21 – The Wrap
- CGM Series: CGM: The Bells and Whistles
- Show Notes and Transcription
- Chart for CGM Devices (From May 2025): DSN Forum
- Tim Street @ Diabettech
That’s it! Let Lou and me know what you loved, what didn’t land, and what you’d like more of. And if someone comes to mind who might benefit, please do share it on.
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