The GNL Podcast
Episode 19, iCGM vs eCGM vs Standardisation by the IFCC: CGM Regulation with Dr. Guido Freckmann
CGM has transformed diabetes care, but how do we know which systems are truly accurate, safe, and comparable? Dr. Guido Freckmann joins John Pemberton to unpick the regulatory landscape and map the road to a global standard.
Listen and Watch
Once you have listened to this episode, the next step is the nuts and bolts of what a standardised evaluation study looks like:
Episode 20, Standardisation of CGM Performance Testing: The Nuts and Bolts
For the foundational context, the CGM regulation FAQ is a useful starting point.
In This Episode
John Pemberton is joined by Dr. Guido Freckmann (Institute of Diabetes Technology, Ulm; former chair of the IFCC CGM Working Group) to unpack:
- Why CE marking in Europe is not a quality standard.
- How the FDA’s iCGM framework (2018) shifted the regulatory bar, with limitations in study design that are now visible in the data.
- Why the proposed eCGM model for Europe risks concentrating the market without fixing accuracy problems.
- The IFCC’s roadmap towards a full ISO standard for CGM, robust, reproducible, and aligned with clinical reality.
Key Themes
CE Mark is Not a Quality Standard
CE marking is a regulatory pathway, not a guarantee of performance. Manufacturers can submit selective data and the results are not made public. This means clinicians and people with diabetes cannot easily compare systems on accuracy grounds.
iCGM (2018): A Step Forward, Now Outdated
FDA iCGM rules set minimum standards, but study design criteria were left vague. Devices can appear accurate by design choices that avoid stressful glucose swings, which is not representative of real use.
Why Standardisation Matters
Standardisation would define not just performance metrics but also how studies are run. It would align CGM systems to the same comparator, capillary or venous, and reduce therapy discrepancies between devices.
The Capillary vs Venous Debate
Capillary glucose reflects what people actually test and what their bodies are exposed to. Venous alignment risks giving a false reassurance of being in range. Whichever is chosen, the comparator must be standardised and bias-corrected.
Clinical Impact
Different CGM systems can give the same time-in-range yet imply very different HbA1c values and complication risk. That undermines trust, confuses therapy adjustments, and makes clinical trial endpoints unreliable.
Looking Ahead
CGM standardisation is in motion, but is unlikely to be implemented before 2030. Until then, clinicians and people with diabetes need to scrutinise study design and remain critical of performance claims.
Quotes from the Episode
“CE marking is not a quality standard. You have to dig into study design, and that’s not practical for the average person with diabetes or most clinicians.”
, John Pemberton
“CGM systems often perform worse at high rates of change than at stable glucose levels. That’s why stress-testing is vital.”
, Dr. Guido Freckmann
“Different CGM systems can give the same time-in-range but very different HbA1c and complication risks. That’s unacceptable.”
, John Pemberton
“Manufacturers can design studies to get good results by avoiding rapid glucose swings. Without rules, accuracy is only on paper.”
, Dr. Guido Freckmann
Resources and Links
Key publications:
- Freckmann et al. (2025), Comparative Analysis of Three CGMs Against Capillary Glucose: found substantial differences between systems reporting the same true glucose.
- Beck et al. (2025 Commentary), Researcher Concerns: raised issues about study design, comparator validity, and the risk of misleading trial conclusions.
- Pemberton et al. (2025 Commentary), Clinical Concerns: highlighted implications for clinical decision-making, T1D screening, and patient confidence.
- Waldenmaier et al. (2025 Response), Author Reaffirmation: confirmed that without traceable comparators and standardised protocols, findings can mislead research and practice.
This content is for educational exploration only. It describes average responses and general principles. It is not medical advice and cannot replace individual clinical guidance from your diabetes care team.