The GNL Podcast

Episode 19, iCGM vs eCGM vs Standardisation by the IFCC: CGM Regulation with Dr Guido Freckmann

A glucose reading sits on the screen and a dosing decision follows from it. Two people, two different sensors, the same true glucose, and the numbers diverge. CGM has transformed diabetes care, but how do we know which systems are truly accurate, safe, and comparable? This conversation maps the regulation behind the reading, and the road to a global standard.

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Want to know what a CE mark actually guarantees about a CGM’s accuracy, and why two sensors reporting the same time-in-range can still imply very different HbA1c?

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Available on Buzzsprout, Apple Podcasts, and Spotify. Guest: Dr Guido Freckmann (Institute of Diabetes Technology, Ulm; former chair of the IFCC CGM Working Group). Host: John Pemberton. Director of Creativity: Anjanee Kohli.

Why this episode exists

If you live with type 1 diabetes, you trust the number on the sensor every time you decide whether to eat, correct, or wait. That trust assumes the systems on the market have all cleared the same bar. They have not. CE marking in Europe is a regulatory pathway, not a guarantee of performance: manufacturers can submit selective data, the results are not made public, and clinicians and people with diabetes cannot easily compare systems on accuracy grounds. The reading looks authoritative; what stands behind it varies more than most people realise.

This episode brings in Dr Guido Freckmann to map that landscape and the work under way to fix it. The published evidence anchors the conversation: Freckmann et al. (2025) found substantial differences between CGM systems reporting the same true glucose, a finding that drew researcher and clinical commentaries and an author response, all set out in the related reading below.

In this episode

John Pemberton is joined by Dr Guido Freckmann, of the Institute of Diabetes Technology in Ulm and former chair of the IFCC CGM Working Group, to unpick how CGM is regulated and where the regulation falls short. The thread the conversation follows is a single question: how do we know which systems are truly accurate, safe, and comparable, and what would it take to answer that with confidence?

The discussion moves from the European CE mark, through the FDA’s 2018 iCGM framework and the proposed eCGM model for Europe, to the IFCC’s roadmap towards a full ISO standard. Along the way it returns repeatedly to study design: the choices a manufacturer makes about how a device is tested often decide what its accuracy claim is worth.

What this episode explores

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 versus 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.

The same true glucose, two different numbers. Different CGM systems can give the same time-in-range but very different HbA1c and complication risk, and the regulation that should catch this does not. As John Pemberton puts it, 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.” Standardisation is the way out, but it is unlikely to be implemented before 2030.

Practical exploration

For people living with type 1 diabetes and their families

When you next meet an accuracy claim or compare two systems, these are the questions worth carrying into the decision.

Treat a CE mark as a permission to sell, not as proof that a system has been tested to the same accuracy bar as another.
Be aware that two sensors can report the same time-in-range yet imply very different HbA1c and complication risk; the number on the screen is a starting point for a conversation, not the end of one.
Where a comparison matters to you, ask whether the accuracy data behind it was independent and peer-reviewed rather than manufacturer-published.

For clinicians and educators

The regulation does not yet do the comparing for you, so the critical appraisal sits with the clinician.

Read accuracy claims through study design: how was the comparator chosen, was it standardised and bias-corrected, and were stressful glucose swings included rather than avoided.
Recognise that the capillary versus venous choice changes what an in-range reading means, and factor that into how confidently you act on a given system.
Advocate for the IFCC and ISO standardisation work, and remain critical of performance claims until a full standard is in place.

About the guest

Dr Guido Freckmann is based at the Institute of Diabetes Technology in Ulm and is the former chair of the IFCC CGM Working Group. His work focuses on the evaluation of CGM accuracy and the regulatory and standardisation framework that governs how these systems are tested and compared. He is lead author of Freckmann et al. (2025), a comparative analysis of three CGM systems against capillary glucose that found substantial differences between systems reporting the same true glucose.