Many devices that sat comfortably in Class I or Class IIa under the Medical Devices Directive end up a class higher. Sometimes two classes higher. Under the Medical Device Regulation. Upclassification under MDR vs MDD is not an accident: Annex VIII of Regulation (EU) 2017/745 rewrote the classification rules, and three changes do most of the work. Rule 11 moved most decision-support and monitoring software into Class IIa or higher. Rule 21 created a dedicated path for substance-based devices that often lands them in Class IIa, IIb, or III. And reusable surgical instruments that were Class I under the MDD are now a Class I reusable (Ir) subcategory requiring Notified Body involvement for reprocessing. If your device was certified under the MDD, assume the class has changed until you can prove it has not.

By Tibor Zechmeister and Felix Lenhard. Last updated 10 April 2026.

TL;DR

  • Annex VIII of Regulation (EU) 2017/745 replaces Annex IX of Directive 93/42/EEC. The rule numbers look similar in places, but the text and the outcomes differ significantly.
  • Rule 11 is the largest single driver of upclassification. Most software that provides information used for diagnostic or therapeutic decisions, or that monitors physiological processes, is now Class IIa or higher. Under the MDD, much of the same software was Class I.
  • Rule 21 is new. It classifies devices composed of substances introduced into the body via a body orifice or applied to the skin and absorbed or dispersed. Many of these devices were Class I or IIa under the MDD. Under MDR Rule 21 they are Class IIa, IIb, or III depending on where they act and what they do.
  • Reusable surgical instruments were Class I under the MDD with no Notified Body involvement. Under the MDR they are Class I reusable (Ir) and require Notified Body oversight for the reprocessing aspects.
  • Regulation (EU) 2023/607 extended the MDD certificate transitional deadlines but does not freeze the classification. When you transition, you transition to the current MDR class, not the historical MDD class.
  • If your device's class has increased, your conformity assessment route, your clinical evidence obligations, and your cost base all change with it. Plan the transition on the new class, not the old one.

The Graz founder who thought they were Class I

A founder Tibor worked with in Graz had a legacy MDD CE mark on a piece of clinical decision-support software. Class I under the MDD. The product had been on the market for years. The team arrived with a plan to "renew" the CE mark under the MDR and keep going. They had budgeted three months and a modest fee for a light-touch technical file update.

The product was Class IIa under MDR Rule 11. It had been Class IIa the moment Annex VIII took effect. The MDD certificate was valid during the transitional period, but when the transition was complete the device would need a Notified Body, a technical documentation assessment, and a QMS audit. The three-month plan became an eighteen-month plan. The modest fee became a five-figure Notified Body engagement. None of this was avoidable, and most of it should have been visible from day one if anyone had read Rule 11 against Annex IX of the MDD.

This is the single most common regulatory shock Tibor sees in transition projects. The founder is not wrong to think the product was Class I. The product was Class I under a different regulation. Under the MDR, the rules changed.

Why MDR classification rules are stricter than MDD classification rules

The MDD classified devices under Annex IX using eighteen rules, written in 1993, amended in 2007 by Directive 2007/47/EC. The drafters did their best with the device landscape of the time. Software was barely in scope. Substance-based devices were not a well-defined category. Reusable surgical instruments were assumed to be cleaned by the user and did not need regulatory oversight of the reprocessing.

The MDR, drafted between 2012 and 2017 and applicable from 26 May 2021, classified devices under Annex VIII using twenty-two rules. The drafters had watched decades of device evolution and had concrete failure modes in front of them. PIP breast implants, metal-on-metal hips, poorly reprocessed instruments, opaque decision-support algorithms. Annex VIII reflects those lessons. The new rules are not arbitrary. Each one addresses a category of risk that the MDD either handled loosely or did not handle at all.

The direction of travel is consistent: where the MDD was ambiguous, the MDR is specific; where the MDD was permissive, the MDR is stricter; where the MDD was silent, the MDR speaks. Upclassification under MDR vs MDD is the statistical consequence. A minority of devices see no class change. A few see a class decrease in narrow cases. The large middle of the distribution moves up by at least one step.

Three rule changes do most of the work. The rest of this post walks through each one.

Rule 11: software as the biggest upclassification case

Rule 11 of Annex VIII is the rule that has reshaped medical device software more than any other single regulatory change in the last decade. Under MDD Annex IX, software was classified by the rule that applied to the function it supported. Most standalone medical software fell into Class I because the default rule for active devices pushed it there unless another rule intervened.

Under MDR Rule 11, software intended to provide information used to make decisions with diagnostic or therapeutic purposes is Class IIa by default. It escalates to Class IIb where those decisions could cause serious deterioration of health or require surgical intervention, and to Class III where those decisions could cause death or an irreversible deterioration of health. Software intended to monitor physiological processes is Class IIa by default, escalating to Class IIb where the monitored parameters are vital and variations could result in immediate danger to the patient.

The practical consequence is that most clinical decision-support software, most diagnostic imaging software, most therapy-planning software, and most patient-monitoring software that was Class I under the MDD is now Class IIa or higher under the MDR. The exceptions. Software that neither supports diagnostic or therapeutic decisions nor monitors physiological processes. Form a narrower category than most SaMD founders assume.

What this means for a founder transitioning an MDD Class I software product: the MDR class is almost certainly not Class I. A Notified Body will be involved. Technical documentation will be assessed. Clinical evidence will be required at the IIa level or higher. The conformity assessment route under Article 52 is different. The cost is different. The timeline is different. Everything downstream of classification changes with the class.

MDCG 2021-24 (Guidance on classification of medical devices, October 2021) works through Rule 11 with concrete examples. Read it against your product before you commit to a transition plan.

Rule 21: substances introduced into or applied to the body

Rule 21 of Annex VIII did not exist under the MDD. It is one of the genuinely new rules introduced by Regulation (EU) 2017/745. It covers devices composed of substances. Or combinations of substances. Intended to be introduced into the human body via a body orifice or applied to the skin, and that are absorbed by or locally dispersed in the human body.

Rule 21 classifies these devices based on where they act and what they do. Devices that achieve their intended purpose in the stomach or lower gastrointestinal tract and are absorbed or locally dispersed are Class IIa, IIb, or III depending on specific criteria laid out in the rule text. Devices applied to the skin or administered nasally or orally that are absorbed or dispersed follow a similar escalating structure. The detailed criteria and thresholds are in the Annex VIII text. Do not work from the summary; read the rule.

Under the MDD, many substance-based devices sat in Class I or Class IIa by default, because no rule specifically addressed the substance-based category. Under MDR Rule 21, the baseline is higher and the escalation criteria are explicit. A nasal spray that was Class I under the MDD can easily be Class IIa or IIb under MDR Rule 21. A gel applied to the skin with an absorbable component can move from Class I to Class IIa or higher. The change is not uniform, and some products do stay where they were, but the default assumption has to be that Rule 21 will move the class up.

Reusable surgical instruments: the new Class I reusable (Ir) subcategory

Under the MDD, reusable surgical instruments. Scalpels, forceps, retractors, clamps that the hospital reprocesses between patients. Were Class I. The manufacturer self-declared conformity. No Notified Body was involved for the device itself. Reprocessing was treated as the user's problem.

Under the MDR, these instruments are still Class I, but they are a distinct subcategory: Class I reusable, or Ir. The class itself did not technically increase, but the regulatory obligations did. A Notified Body is now involved for the specific aspects related to reprocessing: cleaning, disinfection, sterilisation, functional testing, and related validations. The manufacturer must provide instructions for reprocessing that the Notified Body has assessed, and the reprocessing-relevant aspects of the technical documentation are subject to Notified Body review.

The reason this matters for a founder or a manufacturer transitioning from the MDD is simple: the MDD did not require any Notified Body contact for reusable surgical instruments. Under the MDR, you need one. You need a quotation, an application, an assessment, and a certificate for the Ir aspects. The cost is lower than a full Class IIa assessment but it is not zero, and the timeline is not zero. If your plan assumed the same self-certification path you used under the MDD, the plan needs to change.

What upclassification means commercially

Classification is not an abstract regulatory label. It is the input that determines the cost and time of everything downstream. When a device moves from Class I to Class IIa, the commercial consequences are concrete.

Notified Body involvement begins at Class IIa. That means a Notified Body application, a QMS audit, a technical documentation assessment, and annual surveillance audits. The recurring cost base of the company increases. Timelines lengthen by months or quarters. The technical documentation depth increases. Class IIa documentation is more substantial than Class I documentation, and the review is adversarial in a way self-declaration is not.

Clinical evidence requirements escalate at each class boundary. A Class I device can often rely on state-of-the-art literature and a lean clinical evaluation. A Class IIa device needs a more rigorous clinical evaluation and usually some device-specific clinical data. A Class IIb device needs broader and deeper clinical data. A Class III device generally needs clinical investigations, with specific exemptions under Article 61(4)-(6).

Post-market surveillance obligations scale with the class. So do vigilance obligations. So does the scope of the Person Responsible for Regulatory Compliance (PRRC). So does the attention the device attracts from regulators, distributors, and hospital procurement.

A founder whose product moved from Class I to Class IIa under the MDR is not facing a small administrative change. They are facing a regulatory program that is roughly an order of magnitude larger in cost and time than what the MDD required. Planning the transition on the old class is one of the most expensive mistakes a MedTech founder can make.

The 2023/607 transition considerations

Regulation (EU) 2023/607, published in March 2023, amended the MDR transitional provisions in Article 120 and extended the validity of MDD certificates under specific conditions. For legacy devices with a valid MDD certificate on the MDR date of application (26 May 2021), the extended transitional deadlines run until 31 December 2027 for Class III devices and certain Class IIb implantables, and until 31 December 2028 for other Class IIb devices, Class IIa devices, and Class I devices placed on the market in specific categories. Subject to conditions set out in the amended Article 120.

The conditions are not trivial. The manufacturer must have a QMS compliant with the MDR in place by 26 May 2024. The manufacturer must have lodged a formal MDR application with a Notified Body and signed a written agreement by 26 September 2024. The device must continue to comply with the MDD, and there must be no significant changes in design or intended purpose. Post-market surveillance, market surveillance, vigilance, and registration of economic operators and devices now apply in accordance with the MDR during the extended transitional period.

The critical point for classification: Regulation (EU) 2023/607 extends the time you have to transition. It does not freeze the class at the MDD level. When the MDD certificate expires and the device is placed under the MDR, the class is the MDR class, determined by Annex VIII, not the MDD class. The extension is a runway, not a reclassification. A founder who reads the extension as "my Class I MDD software is still Class I" has misread it. The software is Class IIa or higher under MDR Rule 11 from the moment the MDR applies. The extension buys time to complete the transition to that new class. It does not change what the class is.

Use the extension for what it is. Get the QMS compliant. File the Notified Body application on time. Prepare the technical documentation to the MDR standard for the MDR class. And plan the economics of the product on the MDR class, not the MDD class, because that is what will bind the moment the extension ends.

The Subtract to Ship angle on upclassification

The Subtract to Ship framework for MDR compliance treats classification as the second of four passes. For a transition project. A device moving from MDD to MDR. The classification pass is where most of the regulatory shock lives. Run it first, run it against the actual MDR text, and run it without nostalgic reference to the MDD class.

Subtracting in a transition project means cutting every assumption carried over from the MDD. The class is an MDR class. The clinical evidence expectation is an MDR expectation. The technical documentation structure is an MDR structure. The Notified Body relationship is an MDR relationship. Where the MDR requires more, the transition has to deliver more. Where the MDR requires less than the habit accumulated under the MDD, the transition can subtract. But that is rarer than founders hope.

The lowest defensible MDR classification, not the historical MDD classification, is the correct input for the plan. Everything else follows from that.

Reality Check. Is your device upclassified under MDR?

  1. Have you identified the specific MDR Annex VIII rule that applies to your device, and compared it line by line to the MDD Annex IX rule that used to apply?
  2. If your device is software, have you applied Rule 11 to your current intended purpose, not the intended purpose you filed with the MDD certificate years ago?
  3. If your device is a substance introduced into or applied to the body, have you read Rule 21 in full and worked out the class it produces?
  4. If your device is a reusable surgical instrument, have you identified it as Class I reusable (Ir) and planned the Notified Body engagement for the reprocessing aspects?
  5. Have you cross-checked the outcome against MDCG 2021-24 (October 2021)?
  6. Have you quantified the cost and time delta between the MDD path you used and the MDR path the new class requires?
  7. Have you confirmed that your MDD certificate meets the conditions of the extended transitional period under Regulation (EU) 2023/607, including the QMS and Notified Body application deadlines?
  8. Have you planned the transition economics on the MDR class, not on an assumption that the MDD class will carry over?

Frequently Asked Questions

Why are medical devices being classified higher under MDR than under MDD? Because Annex VIII of Regulation (EU) 2017/745 rewrote the classification rules. The MDR has twenty-two rules compared with the MDD's eighteen, and several of them. Particularly Rule 11 for software and Rule 21 for substance-based devices. Introduce higher classes than the equivalent MDD rules produced. Annex VIII also treats reusable surgical instruments as a distinct subcategory (Ir) that requires Notified Body involvement for reprocessing. MDCG 2021-24 (October 2021) walks through the practical application of Annex VIII.

Does Regulation (EU) 2023/607 let me keep my MDD classification? No. Regulation (EU) 2023/607 extended the validity of MDD certificates during a transitional period under specific conditions, but it did not freeze the classification at the MDD level. When the device transitions to the MDR, the class is determined by Annex VIII of Regulation (EU) 2017/745. The extension buys time to complete the transition, not permission to treat the MDR class as if it were still the MDD class.

Which devices are most likely to be upclassified under Rule 11? Clinical decision-support software, diagnostic imaging software, therapy-planning software, and patient-monitoring software. Under the MDD, many of these products sat in Class I. Under MDR Rule 11, software that provides information used for diagnostic or therapeutic decisions, or that monitors physiological processes, is Class IIa by default and escalates to Class IIb or III based on the potential harm from wrong decisions or missed variations.

What changed for reusable surgical instruments under the MDR? They are still nominally Class I, but they are now a distinct subcategory. Class I reusable (Ir). That requires Notified Body involvement for the reprocessing aspects: cleaning, disinfection, sterilisation, and functional testing. Under the MDD, reusable surgical instruments were Class I with no Notified Body involvement at all. The class label did not rise, but the regulatory burden did.

What should I do if my device has been upclassified under MDR vs MDD? Accept the new class and plan the transition on it. Do not attempt to preserve the MDD class through narrow intended-purpose tricks unless a genuine change in use justifies them. The Notified Body will see through it, and reclassification after the fact is significantly more expensive than classifying correctly from the start. Read the MDR rule text, read MDCG 2021-24, apply the rule to your current intended purpose, and build the transition plan against the MDR class.

Sources

  1. Regulation (EU) 2017/745 of the European Parliament and of the Council of 5 April 2017 on medical devices, Article 51 (classification), Article 52 (conformity assessment procedures), Article 120 (transitional provisions, as amended), Annex VIII (classification rules, including Rule 11, Rule 21, and the rules for reusable surgical instruments). Official Journal L 117, 5.5.2017.
  2. Regulation (EU) 2023/607 of the European Parliament and of the Council of 15 March 2023 amending Regulations (EU) 2017/745 and (EU) 2017/746 as regards the transitional provisions for certain medical devices and in vitro diagnostic medical devices. Official Journal L 80, 20.3.2023.
  3. Council Directive 93/42/EEC of 14 June 1993 concerning medical devices, Annex IX (classification criteria). For historical comparison only.
  4. MDCG 2021-24. Guidance on classification of medical devices, October 2021.

This post is part of the Device Classification & Conformity Assessment series in the Subtract to Ship: MDR blog. Authored by Felix Lenhard and Tibor Zechmeister. If your device is caught between an expiring MDD certificate and a higher MDR class, a focused classification session with a sparring partner who has run this transition across dozens of certifications is usually the fastest way to turn the shock into a plan.