CGM has no rival for personal glucose management — but to define future health, it must be standardised.
CGM has transformed personal glucose management to a level never seen before — and no other tool will ever rival it in this role.
But if CGM is to take the next step — so that people can switch between devices and still achieve the same long-term outcomes, and so that metrics like Time-in-Range or average glucose can truly rival HbA1c in predicting future health risk — then standardisation is essential .
This does not mean CGM has a problem. It is already the perfect personal glucose management tool. It simply means that, for CGM to reach its full potential beyond the individual and become a global benchmark for trial end-points and diagnostics, standardisation needs to be strongly considered.
This FAQ explains the current state of CGM regulation across the FDA (Class III, iCGM), CE Marking in Europe, and emerging proposals such as the eCGM Clinician Consensus, the Latin American Clinician Consensus, and British Standards. You’ll learn why iCGM, once groundbreaking, is now outdated; why the choice of comparator (venous vs capillary) matters; why clinician-led initiatives identify the issues and clinical consequences, but arn’t deliver binding standards; and why only an international harmonised standard can secure global trust in CGM accuracy.
Finally, we outline a key issue that will massively impact the diabetes community. What will it will take to get CDRH of the FDA to engage in the conversation of standardisation?
Also, how can people with diabetes, clinicians who support them, and organisations created to advocate for them can drive change?
Listen to these Podcast episodes for the full story from the world’s leading experts on this topic.
Episode 19 – iCGM vs eCGM vs Standardisation by the IFCC: CGM Regulation with Dr. Guido Freckmann
Episode 20 — Standardization of Testing CGM Performance: The Nuts and Bolts
Where is CGM regulation today? Three main pathways currently shape the global CGM landscape:
1. FDA Class III medical device approval (USA)
The highest regulatory bar for medical devices.
Demonstrates safety and effectiveness
Transparent: approval documentation is public in the FDA database.
Devices passing Class III are highly trusted for insulin dosing.
2. iCGM (USA, since 2018)
The only CGM-specific quality standard ever developed.
Introduced three study design “special controls”: pragmatic, loosely defined, but achievable for the market leaders of 2018 (Dexcom G6).
Built on Class III approvals, it codified what safe, effective CGMs could achieve and accelerated approval via the 510(k) pathway.
Crucially, iCGM enabled interoperability — allowing CGMs to link with third-party apps, bolus calculators, and automated insulin delivery (AID) systems.
In 2018, this was transformative: it sped up approvals, drove safe innovation, and fuelled global adoption.
3. CE Marking (Europe)
CE is market authorisation , not a quality standard.
Approval can be based on equivalence to existing devices, a representative sample of data “on file”, often without published peer-reviewed data.
Critically opaque: the evidence remains between the manufacturer and the notified body.
Contrast with the USA: FDA Class III and iCGM approvals are fully transparent, and data can be reviewed by anyone via the online database.
CE approval does not mean poor quality:
Abbott, Dexcom, and Medtronic devices hold CE marking
Roche also launched its newest CGM Accu-Chek SmartGuide with strong accuracy data based on a robust study design (granted, with 48 subjects and 15,000 data points in comparison to the market leaders with 80-200 subjects and 10,000-30,000 data points) – Mader et al (2024)
The CareSens i-SENS also launched with a strong study design and accurate data (30 subjects, 7,000 data points) – Jendrike et al (2025)
But you only know by reading publications, CE marking alone is not enough!
The DSN Forum char t, which gives study design a score out of 5, where a score of at least 4 (ideally 5), is currently the best available tool to assess the study design of CE-marked products.
But as the document makes clear, the DSN Forum chart has real limitations — and future study designs could be manipulated to “game” the system. If I can see how it could be done, so will manufacturers. And honestly, I don’t blame them: they’ll be working within the rules to get their product to market with the best reported accuracy possible. That’s just business. So instead of complaining, we should focus on closing the gaps in the system.
4. Clinician-led consensus: eCGM , Latin American, and BSI
eCGM and Latin American = clinician consensus recommendations aiming to bring in iCGM Special controlsBSI = draft UK guidance to codify iCGM.Both essentially try to globalise iCGM principles.
But:
I support the ideology behind these initiatives — they are well-intentioned attempts to close important gaps.
But the execution is missing: they are not recognised standards, they carry no legal mandate in any jurisdiction, and as splinter efforts, they risk fragmentation, monopolisation of the market, and slowing innovation by locking into outdated 2018 pragmatic rules, not 2025 science.
Notified bodies (~50 in Europe) can only enforce an international harmonised standard .
5. Other markets (e.g. TGA in Australia)
Often follows CE Marking, extending its global influence.
Bottom line
iCGM and FDA III are quality standards and were excellent in 2018, they are still quality standards, but they are outdated by 2025 science.
CE marking is not a quality standard; it provides market access but lacks consistency, robust evaluation, and most importantly, transparency.
eCGM and BSI are opinions and well-intentioned — BUT, they introduce a huge risk of market monopolisation, slowing down innovation, and are not enforceable.
The only binding path is a harmonised international standard .
👉 See: Pemberton et al., Diabetes Obes Metab, 2023 CGM Education Series Podcast with Guido Freckmann on CGM Regulation
Is the 2018 iCGM and FDA Class III outdated for CGM regulation? iCGM raised the bar in 2018, and class III FDA approval is the highest bar for CGM regulation.
Unfortunately, the bar is uneven — and at certain points, limited study designs can slip under the lowest part. In other words, the bar is no longer high enough.
2018 approach : Loosely defined study design, but practical and based on what market leaders could achieve.2025 science : Validated procedures now expose discrepancies that iCGM cannot resolve.Evidence: In the 2025 Diabetes Care head-to-head study , the same patients wore three market-leading sensors — the iCGM-approved Dexcom G7 and Abbott FreeStyle Libre 3, and the FDA Class III–approved Medtronic Simplera. Results showed an 8% difference in time-in-range and a 13% difference in time-in-tight-range. To put that in context: a clinically meaningful difference is just 5%. That means the observed variation is more than twice the threshold of clinical significance, raising the concern that reported outcomes may reflect measurement error alone. These discrepancies are major, and large enough to alter therapy decisions.
This means:
iCGM was essential for accelerating innovation and interoperability.
But it now risks holding us back if not updated in line with validated procedures.
👉 Read: Diabetes Care, 2025 Pemberton et al., Diabetes Care, 2025 , Beck Diabetes Care 2025, Waldenmaier et al Diabetes Care 202 5
Why does the comparator matter (device bias, venous vs capillary samples)? Recent data show that even these analysers can exceed the accepted glucose testing bias threshold of <2.1%. Without retrospective calibration or correction, venous plasma measurements — even from YSI or Cobas Integra — are not sufficiently low-bias to ensure that the comparator truly reflects actual venous glucose levels. In other words, the very reference standard we depend on introduces systematic error.
Important note: Since the 2023 Guidelines and Recommendations for Laboratory Analysis in the Diagnosis and Management of Diabetes Mellitus , it has been clear that glucose measurements must exhibit a bias of <2.1% to be considered effective as reference methods.
Recent recommendations h
More importantly, with retrospective calibration and correction , handheld blood glucose meters (that you and I use) can achieve the <2.1% bias threshold. This means that what was considered sound methodology in 2018 — relying on venous samples measured by “lab grade” analysers — no longer meets today’s bias requirements. In fact, calibrated capillary blood glucose now offers a more robust comparator. Independent thought leaders have recommended a shift to using capillary as the comparator (reference) for these reasons:
Venous glucose doesn’t reflect lived reality: People with diabetes have always checked CGM accuracy — and historically corrected insulin doses — using capillary blood glucose. Every manufacturer’s Instructions for Use (IFU) clearly state that if there is doubt about CGM accuracy, confirm with a capillary blood glucose meter.
Why? Because a meter that meets ISO 2013 standards is still more accurate than CGM at measuring the most important thing: capillary blood glucose. And I’ve never seen anyone walking around with an indwelling catheter in their forearm to check venous glucose — unless I’ve been wearing blinkers.
Capturing peaks : Capillary is at least 10-30% higher than venous glucose postprandial spikes . Remember, the human body is exposed to the slowest-moving glucose in the capillaries — and this is where microvascular damage occurs: the eyes, kidneys, feet, and hands. Post-meal highs, rather than fasting levels, correlate more strongly with HbA1c and, therefore, future complications, in a systematic review of 14 quality studies.
If we validate and calibrate CGM against venous glucose, we miss what matters most: true glucose exposure in the capillary circulation. As a result, those adjusting insulin manually and automated insulin delivery (AID) systems responding to CGM glucose levels cannot respond appropriately to reduce risk.
In my view, this is the single most important reason to switch to capillary comparators. They reflect the lived reality for people with diabetes — the very people these systems are designed for. Effective treatment decisions can only be made if we measure what drives damage.
Right now, CGMs aligned to venous comparators under-report capillary exposure by ~8% in time-in-range and ~13% in time-in-tight-range. That is not acceptable when the main drivers of complications are precisely what we need to capture.
I’ve said it a thousand times: “What gets measured gets managed.
Consistency : A 70% time-in-range result on a venous-aligned system ≠ 70% on a capillary-aligned one.Bias : Data clearly demonstrates that with retrospective calibration to higher-order reference materials, capillary comparators can achieve <2.1% bias — outperforming venous comparators that, without correction, are still widely (but incorrectly) treated as the gold standard.
What are eCGM/Latin American/BSI CGM recommendations (and why is it not enough)?
“eCGM” is a clinician consensus document being promoted in Europe and a Latin American version . But:
It has no regulatory force — it is guidance only .
BSI proposals follow the same path.
Both are built on 2018 iCGM science.
They prioritize venous comparators, risk monopolizing the market, and don’t reflect patient experience.
British Standards Institution (BSI) for CGM
The BSI proposals refer to draft UK guidance documents that attempt to codify “eCGM” (expert consensus CGM criteria) into a framework similar to iCGM. But — as you’ve already noted:
Not harmonised international standards ,Carry no legal mandate , and
Risks of creating fragmentation if adopted in parallel to CE marking.
Most importantly, neither eCGM nor BSI can ever be mandatory. Only an international harmonised standard can bind notified bodies.
Are we at a pivotal point?
Yes. We now face two choices:
Option A: Stay with CE marking + iCGM and introduce fragmentation with consensus efforts
Pros : Convenient, easy, fits current inertia, will result in short-term stability and consistency in quality.Cons :
Monopolization of the market by the 2-3 manufacturers
Ruling out our robustly assessed CGM system, such as the Accu-Chek SmartGuide and one other as described above.
Fragmentation between regulatory systems.
Eroding trust in CGM.
Inability to use CGM as trial endpoints – no meta-analysis of studies that use different sensors
Overall, failure to realise the full potential of CGM.
Tools like the DSN Forum chart FIND initiative backed by the IDF
Standardise the comparator.
Correct for comparator bias.
Deliver cross-device comparability.
Arbitrary cut-offs can be met with a manipulated study design (e.g., recruiting participants low or high in-clinic).
Bottom line: we will end up with patchwork tools, not a true standard.
Option B: Build an international Harmonised Standard
Backed by IFCC 2025 methodology :
Capillary comparator aligned to patient experience.Bias correction (<2.1%).Validated procedures (meal + insulin challenges on the same visit).Dynamic Glucose Region Plot (DGR) to map sensor accuracy across the zones where real-world decisions happen:
Low and going lower → hypoglycaemia treatment.
Low but recovering → alarm reliability.
High and going higher → correction doses.
High and sustained → prolonged hyperglycaemia detection.
Challenges :
Manufacturers may face pressure for dual approvals (iCGM + International standard). This would face real and fair opposition — it would be costly to sustain a two-tier regulatory system. I don’t blame the leading manufacturers for digging in their heels here.
Solution: The CRDH of the FDA needs to come to the table — to either help negotiate and produce a single global standard that covers all markets, or to agree that any product meeting the a new international standard will also be accepted under iCGM or FDA Class III. If a manufacturer only wants U.S. approval, they can stick with the current pathway — but realistically, no company will want to limit itself to the U.S. market alone.
Multicentre sites must standardise methodology.
Solution: Certify centres to run harmonised protocols. Remember, study sites are well-compensated to run these trials. With clear protocols, guidance, and audit accountability, it can be done. We’ve already seen this with HbA1c: standardised measurement enabled the DCCT to deliver solid, trusted findings, sparking decades of research that led to intensive management and longer, healthier lives for people with diabetes. We now need the same for CGM metrics if we want to move forward.
Cost — who will fund performance metric validation, the development of standardised protocols, and the accountability systems needed for sites to run them effectively? Here are several potential funding streams:
Manufacturers (primary contributors):
At present, manufacturers already fund the bulk of accuracy and performance studies.
Since they profit most from people with diabetes using these systems, it is fair that they contribute proportionally to market share.
Philanthropic foundations:
Organizations that believe CGM is the future of diabetes care can step in.
Examples include the Helmsley Charitable Trust, IDF, Breakthrough T1D, Diabetes UK, and national/local charities.
These groups have a track record of providing core resources and seed funding for projects with global benefit.
Public–private partnerships:
Governments and health systems may co-fund standardisation work, given the long-term savings from better outcomes.
Partnering with industry spreads costs and builds accountability.
Independent research grants:
EU Horizon, NIH, and Wellcome Trust calls could be leveraged to support multicentre trial standardisation.
Crowd-based or pooled contributions:
Professional societies (EASD, ADA) and advocacy networks could provide targeted funds to accelerate specific steps, such as protocol audits.
Bottom line: This is the HbA1c moment for CGM. Just as HbA1c became the harmonized gold standard for outcomes, CGM needs an international standard to become a trusted global endpoint.
What will it take for global regulators — especially the FDA — to act?
The only binding route is a harmonised international standard . So,
People with diabetes, clinicians, and organisations must push regulators (FDA, EMA, MHRA) and manufacturers.
The ask: FDA to consult with IFCC to update or recognize a harmonized global standard.
Timeline
No revocation of current approvals, grandfather clauses, and use tools such as DSN Forum Chart to support re-imbursement. Not perfect, but we live in an imperfect world.
International standard phased in by 2030 with clear guidance, tools, and accountability.
The long game
CGM will become the primary clinical endpoint in diabetes care and trials. Without harmonization, we risk stagnation. With it, CGM can transform the diabetes research just as HbA1c did.
Q7: What can you do to make CGM standardization happen?
Regulation does not move on its own. Every breakthrough in diabetes care — from HbA1c becoming the global gold standard, to insulin pumps being recognised as safe, to flash and CGM moving from “adjunctive” to “non-adjunctive” — only happened because people with diabetes, clinicians, and organisations pushed for it.
Why your voice matters
Regulators listen when patient communities speak with one voice.
Organisations (charities, professional societies, advocacy groups) amplify that voice.
Without visible demand, regulators assume the status quo is “good enough.”
Right now, iCGM and CE marking approval pathways are convenient for manufacturers and regulators. But they are not enough for people living with diabetes who rely on CGM for safe decisions and who deserve a fair comparison across devices.
What success looks like
A harmonised international standard for CGM accuracy, built on IFCC methodology.
One global comparator: capillary glucose, aligned to lived experience.
Bias correction (<2.1%) to ensure fairness across all sensors.
Standardised protocols — meal, insulin, exercise challenges in real-world conditions.
A Dynamic Glucose Region Plot (DGR) so accuracy is mapped where it matters: alarms, hypoglycaemia, sustained highs.
How you can help
Share this with:
People with diabetes and their families.
Clinicians and educators.
National diabetes organisations, charities, and advocacy networks.
Ask your organisations to endorse. Professional societies, advocacy groups, and industry-independent charities add weight that regulators cannot ignore.Spread awareness. Share podcasts, infographics, and FAQs like this one. The more consistent the message, the harder it is to ignore.Hold manufacturers accountable. Ask them directly whether they will commit to internationally aligned accuracy studies.
This is a watershed moment!
This is the HbA1c moment for CGM. Just as HbA1c became the universally trusted outcome for diabetes trials, a harmonised international standard will make CGM the trusted global endpoint for care and research.
Bottom line
Without pressure from people with diabetes, regulators, and manufacturers will stay in 2018.
With awareness there is no pressure. We can reach 2030 with a standard that unlocks the full promise of CGM.
Acknowledgements
This document reflects my own views and responsibility. The individuals listed below have shaped my understanding of CGM regulation and diabetes research through their work, discussions, and collaborations.
Their inclusion here does not imply endorsement of the content or conclusions. Its just don’t like to credit for standing on the shoulders of giants!
Acknowledged (alphabetical order):
Written by John Pemberton (editing support from Chad, my AI ChatGPT Assistant developed over 4 years of trial and error)
