--- title: MDR vs. MDD: What Changed and Why It Matters for Your Startup description: The EU MDR replaced the MDD with stricter classification, clinical evidence, and oversight requirements — here are the specific changes that affect MedTech startups. authors: Tibor Zechmeister, Felix Lenhard category: MDR Fundamentals & Regulatory Strategy primary_keyword: canonical_url: https://zechmeister-solutions.com/en/blog/mdr-vs-mdd source: zechmeister-solutions.com license: All rights reserved. Content may be cited with attribution and a link to the canonical URL. --- # MDR vs. MDD: What Changed and Why It Matters for Your Startup *By Tibor Zechmeister (EU MDR Expert, Notified Body Lead Auditor) and Felix Lenhard.* The Medical Device Directive (MDD 93/42/EEC) governed medical devices in Europe for over 25 years. The Medical Device Regulation (MDR, Regulation (EU) 2017/745) replaced it. If you are a startup entering the MedTech market, you need to understand exactly what changed, because the differences determine your regulatory burden, your timeline, and your budget. Here is the direct comparison, organized by the areas that matter most to founders building their first medical device. ## What Is the Fundamental Legal Difference Between MDD and MDR? The MDD was a directive. In EU law, a directive sets goals that each member state must achieve, but each country can write its own national laws to implement it. This meant that the practical application of medical device rules varied from country to country. Germany implemented the MDD differently from France, which implemented it differently from Italy. For manufacturers, this created inconsistency. The MDR is a regulation. A regulation applies directly and identically in every EU member state. There is no national transposition. The same text, the same requirements, the same rules — whether you are in Vienna, Berlin, or Paris. For startups, this is actually a simplification: you learn one set of rules, and they apply everywhere. But that is where the simplification ends. The content of the MDR is significantly more demanding than what the MDD required. ## How Did Classification Rules Change? Under the MDD, classification followed Annex IX of the directive, with 18 classification rules. The MDR moved classification to Annex VIII and expanded to 22 rules . The most consequential change for startups: **software classification**. Under the MDD, standalone software was largely unregulated or fell into Class I. The MDR introduced Rule 11, which classifies software based on the decision it supports: - Software intended to provide information used to make decisions with diagnosis or therapeutic purposes is classified as Class IIa at minimum - If those decisions could cause death or irreversible deterioration, the software is Class III - If the decisions could cause serious deterioration, the software is Class IIb This single rule change pulled thousands of software products from unregulated or Class I territory into Class IIa or higher. For a software startup, this means you almost certainly need a Notified Body — which was rarely the case under the MDD. Other notable reclassifications: - **Devices incorporating nanomaterials** now follow specific rules that often push them into higher classes - **Active implantable devices** that were previously under a separate directive (AIMDD 90/385/EEC) are now absorbed into the MDR - **Devices with no intended medical purpose** listed in Annex XVI (aesthetic lasers, dermal fillers, colored contact lenses, etc.) are now regulated under the MDR — they were not regulated at all under the MDD For a full breakdown of how classification works under MDR, see our post on [MDR Conformity Assessment Routes: Which Path Is Right for Your Device?](/blog/031-mdr-conformity-assessment-routes). ## How Did Clinical Evidence Requirements Change? This is the area where Tibor sees the biggest impact on startups. Under the MDD, clinical evaluation was required, but the bar was relatively low. A literature-based clinical evaluation — reviewing published studies on similar devices — was often sufficient, even for moderate-risk devices. Demonstrating equivalence to another device was a common shortcut, and the requirements for proving equivalence were loose. The MDR changed this in three specific ways: **1. The equivalence bar is now much higher.** Article 61(5) of the MDR states that if you claim equivalence to another manufacturer's device, you must have a contract with that manufacturer giving you sufficient access to their technical documentation to justify the equivalence claim . Under the MDD, you could claim equivalence to a competitor's device based on publicly available information. Under the MDR, that path is essentially closed unless the competitor voluntarily shares their data — which they almost never do. **2. Clinical investigations are expected for higher-risk devices.** For Class III and implantable devices, the MDR presumes that clinical investigations (actual clinical studies with the device) are needed unless specific exceptions apply. Article 61(4) and (6) define these exceptions . The bar for justifying why you do not need clinical investigations is high. **3. Post-market clinical follow-up (PMCF) is mandatory and substantive.** Under the MDD, PMCF was a concept. Under the MDR, it is a detailed requirement with its own annex (Annex XIV, Part B) and must be a genuine ongoing activity — not a statement that "no safety issues have been reported." Notified Bodies actively audit PMCF plans and reports. For startups, the practical impact is significant. If you cannot demonstrate equivalence (and you usually cannot, because you do not have access to a competitor's technical documentation), you need your own clinical data. Generating clinical data takes time and money. This must be factored into your product development timeline from the very beginning. ## What Changed About Technical Documentation? Under the MDD, the technical file structure was flexible. The MDD set out what needed to be included but did not prescribe a rigid structure. This led to what auditors sometimes call the "treasure hunt" — documents scattered in random order, forcing the reviewer to search for required information. The MDR tightened this significantly. Annex II defines the structure of the technical documentation, and Annex III defines the structure of the post-market surveillance documentation. Together, they create a clear, comprehensive framework that every manufacturer must follow. Key differences for startups: - **Annex I** (General Safety and Performance Requirements — GSPRs) replaced the Essential Requirements of the MDD. There are more requirements, they are more specific, and you must explicitly address each one in your documentation — including those that do not apply to your device, with a justification for why they do not apply . - **Benefit-risk analysis** is now explicitly required as part of the technical documentation (Annex I, Chapter I) and must be documented with a clear methodology, not just a general statement. - **Design and manufacturing information** must be more detailed, including a complete description of the manufacturing process, validation of the manufacturing process, and identification of critical suppliers. We cover the full structure of MDR technical documentation in our upcoming posts on this topic. ## How Did Post-Market Requirements Change? Under the MDD, post-market surveillance was largely a formality for many manufacturers. You maintained a vigilance system, reported serious incidents, and filed the occasional Field Safety Corrective Action (FSCA). The system worked on trust, with limited active enforcement. The MDR created a comprehensive post-market surveillance framework that is actively audited: - **Article 83:** Every manufacturer must plan, establish, document, implement, maintain, and update a post-market surveillance system. This is not a suggestion. - **Article 85:** Post-market surveillance reports are required for Class I devices. - **Article 86:** Periodic Safety Update Reports (PSURs) are required for Class IIa, IIb, and Class III devices. The frequency depends on the class — annually for Class III and implantable devices, with the possibility of less frequent updates for Class IIa after agreement with the Notified Body . - **Article 87:** Serious incident reporting timelines are strict — 15 days for serious incidents, 2 days for serious public health threats, 10 days for trends . For startups, this means you must build a post-market surveillance infrastructure alongside your product development — not after market launch. The Notified Body will audit your PMS system during the initial certification audit. ## What Changed About Notified Bodies? The MDD system had approximately 80 Notified Bodies across Europe . The MDR imposed much stricter designation requirements, and the re-designation process under the MDR has been slow. As of early 2026, there are approximately 40 designated MDR Notified Bodies . Fewer Notified Bodies means longer wait times for certification. Some Notified Bodies have backlogs exceeding 12 months just for initial contact. This is one of the most significant practical impacts for startups — your timeline is not just determined by how fast you can prepare your documentation, but by how quickly a Notified Body can schedule your audit. The MDR also strengthened Notified Body oversight: - **Unannounced audits** are now mandatory (Article 52(8)) - **Technical documentation reviews** must happen for a representative sample of devices, not just during initial certification - **Notified Bodies must have in-house competence** for the devices they certify — they cannot outsource everything to subcontractors For more on this, read [What Is a Notified Body and How Do They Audit Your Startup?](/blog/014-what-is-notified-body) and [The Notified Body Bottleneck: Strategies for Startups Facing Long Wait Times](/blog/016-notified-body-bottleneck). ## What Changed About Traceability and Transparency? The MDR introduced two major systems that did not exist under the MDD: **Unique Device Identification (UDI):** Every device must carry a UDI — a unique code that allows it to be traced through the entire supply chain. The implementation timelines are staggered by risk class . **EUDAMED:** The European Database on Medical Devices is intended to be a central repository for device registrations, certificates, clinical investigations, post-market surveillance, and vigilance reports. EUDAMED has been delayed multiple times and is being deployed module by module . When fully operational, it will make device information publicly accessible — a major transparency increase over the MDD system. ## The Net Impact for Startups Here is the honest summary, from the perspective of someone who has guided over 50 companies through this transition: The MDR is harder. It requires more documentation, more clinical evidence, more post-market infrastructure, and more interaction with Notified Bodies. The timeline from concept to CE marking is longer — 18 to 36 months is realistic for most devices, compared to 12 to 18 months that was common under the MDD for lower-risk devices . But the MDR is also clearer. The requirements are explicit. The structure is defined. If you read the regulation and follow it systematically, there are no hidden traps. The founders who struggle are those who underestimate the scope, those who start regulatory work too late, and those who treat compliance as a burden rather than a design constraint. The MDR is not going away. It is not going to be softened. If anything, enforcement is tightening as the system matures. The startups that succeed are those that build the MDR into their product development process from the first day — not as an afterthought, but as the framework that shapes every decision. For the full timeline of MDR milestones, see our next post: [The Complete MDR Timeline: Key Dates Every MedTech Founder Must Know in 2026](/blog/003-complete-mdr-timeline). --- *This post is part of the [MDR Fundamentals & Regulatory Strategy](https://zechmeister-solutions.com/en/blog/category/mdr-fundamentals) cluster in the [Subtract to Ship: MDR Blog](https://zechmeister-solutions.com/en/blog). For EU MDR certification consulting, see [zechmeister-solutions.com](https://zechmeister-solutions.com).*