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Differences Between Software as a Medical Device (SaMD) and Software in a Medical Device (SiMD)

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The nuances between Software as a Medical Device (SaMD) and Software in a Medical Device (SiMD) can sometimes perplex professionals in the life sciences industry. Despite their apparent similarities, they represent two different concepts. It's a crucial differentiation that significantly impacts regulatory compliance, risk assessment, and validation processes. For companies involved in medical devices, determining whether their product falls under SaMD or SiMD category isn't just a matter of regulatory compliance - it's essential for ensuring the safety, efficacy, and quality of what they provide.

This blog post aims to help clarify what sets SaMD and SiMD apart, providing easy-to-understand explanations so you can better understand and use these categories with confidence. Before delving deeper into this blog, how do we define SaMD and SiMD?

What is SaMD?

Software as a Medical Device (SaMD) is specifically designed for medical purposes and operates independently of any physical medical device hardware. It can be deployed on various platforms like smartphones, cloud-based systems, or desktop computers.

The defining characteristic of SaMD lies in its application for diagnosing, treating, or managing health conditions, regardless of the technological platform it uses. Regulatory agencies like the FDA (U.S. Food and Drug Administration) and EMA (European Medicines Agency) have established detailed guidelines for the development and validation of SaMD, aiming to ensure its safety and efficacy.

Examples of SaMD

  • Diagnostic applications that interpret imaging data to detect cancer.

  • Decision support software that analyzes patient data to recommend medication dosages.

  • Health monitoring apps that measure and track blood glucose levels, issuing warnings when readings are abnormal.

What is SiMD?

Software in a Medical Device (SiMD) refers to software that is an integral part of a hardware medical device, essential for its operation. This software is key to the device's primary function, playing a direct role in its performance and reliability.

During the regulatory approval process, SiMD is assessed as part of the overall device's regulatory submission and is subject to the same quality and safety standards as the device itself.

Examples of SiMD

  • Firmware that controls the dosage and timing settings in an infusion pump.

  • Software within an ultrasound machine that processes and enhances images in real time.

  • The operating system within a blood analysis device that manages tests and interprets the data.

Medical Software Not Falling Into These Categories

Not every piece of medical software is strictly SaMD or SiMD. Some software facilitates research, promotes wellness, or serves administrative purposes.  None of which align with the SaMD or SiMD classifications. For example, tools for clinical research and data analysis might not be considered SaMD or SiMD, because they don’t directly contribute to diagnosing, treating, or managing diseases. 

Complexity in Classification

Even with clear definitions, figuring out if software is SaMD or SiMD can be tricky for a number of reasons:

  • Interconnected Functionality: Modern medical devices often rely heavily on software to perform their intended functions. In many cases, the software is deeply integrated into the device's hardware, blurring the distinction between the two. It can be difficult to determine whether the software is merely a component of the device (SiMD) or if it functions independently as a medical device itself (SaMD).

  • Evolution of Technology: Advances in technology continually change how medical devices and software work. New functionalities and capabilities may emerge that challenge traditional classifications. As technology evolves, regulatory frameworks may struggle to keep pace with these changes, leading to ambiguity in classification criteria.

  • Complex Use Cases: Some medical software serves diverse purposes, making it challenging to categorize as either SaMD or SiMD. For example, software used for patient monitoring may also include diagnostic algorithms or features that support decision making. Determining the software's primary function and intended use can be complex in such cases.

  • Regulatory Variability: Different regulatory bodies may have varying definitions and criteria for classifying medical software. This variability can lead to discrepancies in classification decisions, especially for software products intended for global markets. Navigating these differences adds another layer of complexity to the classification process.

  • Risk Assessment: The classification of medical software depends on the level of risk associated with its use. However, assessing risk factors such as patient safety, product quality, and data integrity can be subjective and open to interpretation. Determining whether the software poses low, moderate, or high risk requires careful consideration of various factors, further complicating the classification process.

  • Software Changes: Software is inherently dynamic, capable of receiving updates, enhancements, and patches over its lifecycle. Changes to software functionality or intended use may necessitate reevaluation of its classification status. The dynamic nature of software presents challenges in maintaining accurate and up-to-date classifications over time.

Navigating the Validation Process: Key Considerations

At this point, you should be familiar with the definitions that characterize these two types of software, as well as the main challenges you may encounter when classifying them.

From the standpoint of the validation process, regardless of the type of software you are dealing with, here are the steps to follow to cover all aspects of the good practices in terms of software classification:

  1. Conduct a Comprehensive Assessment: Perform a thorough assessment of the software's intended use, functionality, and impact on patient care. Consider factors such as the software's primary purpose, level of autonomy, intended user, and potential risks associated with its use.

  2. Evaluate Risk: Assess the level of risk associated with the software product, including risks to patient safety, product quality, and data integrity. Determine whether the software poses low, moderate, or high risk based on its intended use and functionality.

  3. Document Decision-Making Process: Maintain detailed documentation of the decision-making process used to classify the software product. Document key considerations, criteria, and rationale for determining whether the software should be classified as SaMD or SiMD.

  4. Engage Stakeholders: Involve relevant stakeholders throughout the classification process, including software developers, regulatory affairs professionals, healthcare providers, and legal experts. Collaborate to ensure a comprehensive understanding of the software's functionality and intended use.

  5. Seek Regulatory Feedback: Consider seeking feedback from regulatory authorities or agencies early in the development process. Engaging with regulatory bodies can help clarify classification requirements and ensure alignment with regulatory expectations.

  6. Monitor Regulatory Updates: Stay informed about changes in medical device regulations and guidance documents that may impact software classification. Continuously monitor regulatory updates to ensure compliance with evolving requirements.

  7. Consider Precedents and Case Studies: Review precedents and case studies of similar software products that have undergone classification processes. Learn from past experiences and use them as reference points when classifying your software product.

Key Takeaways

The distinction between SaMD and SiMD affects every aspect of the product lifecycle, from development to deployment. Recognizing these differences is essential for delivering innovative and safe products, while also setting new standards for excellence in technology.

Summarizing the Differences





Software that serves a medical purpose without being part of a hardware medical device.

Software integrated into, and necessary for the functioning of, a hardware medical device.

Regulatory Focus

Independent regulatory pathway focusing on the software's medical purpose.

Assessed as part of the hardware medical device's regulatory submission.


Software that can diagnose diseases, suggest treatments, or monitor health through apps.

Firmware in medical instruments, embedded software in diagnostic equipment.

As experts in regulatory compliance, we're here to guide you through understanding best practices and how to evolve within this industry whether you are a SaMD/SiMD vendor or a customer of these types of products.

If you want to dive deeper into this topic, we would love the chance to have a conversation with you and share our knowledge. For more information, click here or reach out to us directly at info@innnovx.org.

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