What many people consider to be accessories differs from the definition of the term in the MDR.
This article gives you an overview of the definition of the term, the regulatory requirements, and typical questions.
1. Definition of the Term “Accessory”
a) Accessory According to the MDR
The Medical Device Regulation (MDR) defines the term as follows:
“Accessories for medical devices are objects, substances, and preparations made from substances that are not medical devices themselves as defined in number 1 but are intended by the manufacturer to be used with a medical device so that it can be used in accordance with the manufacturer’s specified intended purpose of the medical device.“
b) Accessory According to MDR
The Medical Device Regulation (MDR) defines the term in almost the same words:
“accessory for a medical device’ means an article which, whilst not being itself a medical device, is intended by its manufacturer to be used together with one or several particular medical device(s) to specifically enable the medical device(s) to be used in accordance with its/their intended purpose(s) or to specifically and directly assist the medical functionality of the medical device(s) in terms of its/their intended purpose(s);”
Source: MDR
Examples of accessories include foot switches and remote controls for operating tables, cleaning agents, tools for installing, calibrating, and maintaining medical devices, and special supports and covers.
Please read below for more information on how accessories and spare parts are distinguished.
c) “Accessory” According to the FDA
The term “accessories” refers to products that—according to the FDA website on Medical Device Accessories—support, supplement, and/or enhance the performance of another device, sometimes referred to as the “parent device.”
For the FDA, a medical device is
“an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including a component part, or accessory which is:
- […] intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, in man or other animals, or
- intended to affect the structure or any function of the body of man or other animals, and which does not achieve its primary intended purposes through chemical action within or on the body of man or other animals and which is not dependent upon being metabolized for the achievement of any of its primary intended purposes.“
This makes it clear that an accessory is also a device and that the corresponding regulations apply. The FDA also explicitly defines the term accessory:
“A finished device that is intended to support, supplement, and/or augment the performance of one or more parent devices.”
Explanation
The term “support” is to be understood in several ways:
- Necessary requirement
The medical device cannot be used without the accessories, i.e., the accessories are a requirement for its use. - Non-necessary requirement
The medical device can also be used without the accessory, e.g., an infusion pump (medical device) that can be used without the corresponding stand (accessory). - Expansion of functionality
The accessory expands the functionality but not the intended purpose of the medical device. For example, a pulse oximeter (accessory) can expand the functionality of a monitor (it can now also display oxygen saturation) but not its intended purpose (to display and record physiological parameters). - Improvement of functionality
Lastly, an accessory can improve the function of a medical device. For example, a software program that adds color or contrast filters can improve the performance of the device that provides the raw images.
These examples come from the FDA guidance document “Medical Device Accessories – Describing Accessories and Classification Pathways.”
Example
The FDA periodically publishes lists of accessory products. As of August 17, 2026, this list included seven accessory products that are to be classified as standalone Class I devices. These would then be exempt from the 510(k) premarket notification requirement; the comment period runs until October 16, 2026.
To the best of our understanding, the FDA’s notice in the Federal Register, the new FDA website, and the 2017 guidance document still cite different criteria. The crux of the matter appears to be whether design controls are required (which would continue to apply even to Class I software-based accessories, for example).
2. Regulatory Requirements
a) MDR
With regard to accessories, the MDR requires:
- Manufacturers to list the intended accessories in the technical documentation
- and to consider them in the clinical evaluation.
- The instructions for use must explain how to use the accessories.
Like the MDD, the MDR also insists that manufacturers meet the general safety and performance requirements and demonstrate this as part of a conformity assessment procedure – the same as for any medical device.
b) FDA
Approval
The FDA has a similar view:
“The FDA has a long-standing rule which says that anything intended to be used as an accessory to a medical device is itself a medical device and regulated to the same level as the device it accessorizes.”
FDA guidance document (see below)
The FDA permits the approval of an accessory both together with the “parent device” or via its own approval procedure.
“A finished device whose performance is supported, supplemented, and/or augmented by one or more accessories.”
Source: FDA guidance document (see below)
It is, therefore, also possible that an accessory may have to undergo a Premarket Approval (PMA), Premarket Notification (PMN, 510(k)), or a De Novo Procedure.
Classification
According to the above quote, the FDA generally classifies accessories in the same class as the so-called “parent device” unless the accessory risks differ from those for the main product/parent device. In this case, the accessory is classified independently according to these risks.
Another reason for a different classification is if the accessory is intended for many “parent devices.”
More information can be found in the FDA Guidance Document “Medical Device Accessories – Describing Accessories and Classification Pathways.“
3. Can Software be an Accessory for a Medical Device?
a) Europe
Question: Is (stand-alone) software for the calibration of a medical device a medical device itself? Or is it an accessory for a medical device? Or neither?
This simple-sounding question is not so easy to answer. To do so, we have to look at the history of the definition of terms.
Unlike the current definition, the MPG defined the term as follows in its first edition in 1994:
“Accessories for medical devices are objects, substances, preparations made from substances, and software that are not medical devices themselves as defined in number 1 but are intended by the manufacturer to […]”
MPG
With the amendment of the MDD in 2007, the definition of a medical device was expanded to make it clearer that software can also be a medical device. This can be found in the justification for the amendment. The implementation of the MPG in 2009 adopted this definition in the wording and also adapted the definition of accessories in the same amendment by deleting “software” there. However, this should not mean that software can no longer be an accessory.
Conclusion: The problem results from adopting the definition of accessories in the MPG and is a misinterpretation of the 2009 amendments.
The recitals of the MDR state:
“The qualification of software, either as a device or an accessory, is independent of the software’s location or the type of interconnection between the software and a device.”
Recital (19) MDR
b) USA/FDA
In the guidance document on accessories mentioned previously, the FDA explicitly emphasizes that standalone software (“Software as a Medical Device” SaMD) can also be an accessory but does not have to be. However, if the software is to be used for medical purposes without hardware, the software itself is a medical device and not an accessory.
4. Same Manufacturer for a Medical Device and its Accessory
Question: Does the manufacturer of an accessory have to be the same as the manufacturer marketing the corresponding medical device? In other words, would the following definition of accessories have to be supplemented by the words in brackets?
“Accessories for medical devices are objects, substances, and preparations made from substances that are not medical devices themselves as defined in number 1 but that are intended by the manufacturer (of the accessory) to be used with a medical device (the “main product”) so that this (“main product”) can be used in accordance with the intended purpose of the medical device (“main product”) as defined by the manufacturer of the accessory.”
Answer: No. It cannot be assumed that it is meant to be the case that it must be the identical manufacturer. This is also evident in “reality” that these are often different manufacturers. For dialysis machines, for example, the market for blood hoses is a competitive one.
By the way, this is precisely why many manufacturers design their devices in such a way that it is difficult for manufacturers of suitable accessories, especially disposable accessories, and users are forced to buy the “original accessories.”
5. Accessories Versus Spare Parts
Question: What happens if you sell a peristaltic pump for a dialysis machine? Is it an accessory or a spare part?
- It could indeed be an accessory because, by definition, an accessory is an object intended by the manufacturer to be used with a medical device so that the medical device can be used for the intended purpose specified by the manufacturer. A peristaltic pump is certainly used to ensure that the dialysis machine can be used for its intended purpose.
- It could also be a spare part because a defective peristaltic pump has to be replaced.
The first answer to the question is: It doesn’t have to be “either-or.” Products can be both spare parts and accessories. Let’s take a look at a specific case:
- If you do not sell the peristaltic pump independently but only offer it as a spare part, then it is a spare part. This means that you do not have to subject the peristaltic pump to a separate conformity assessment procedure. Instead, you can check the conformity of the entire dialysis system, including the peristaltic pump.
- If, on the other hand, you market the peristaltic pump as an optional product, you need to carry out a conformity assessment. It is then an accessory. The fact that it can be used as a spare part does not change anything.
Whether a peristaltic pump is a spare part or an accessory depends on how you communicate and declare it.
6. Risk Management for Accessories
Risk management for an accessory cannot be done without knowing the medical device with which it is intended to be used.
Nor should risk management repeat the risk management elements for the device but add the elements that are specific to the use and design of the accessory. Therefore, the FMEA is a helpful risk analysis method for the accessory.
Revision History
- 2026-09-07: MPG sections removed; numbering updated accordingly. Section 1.b) (“FDA”) restructured, expanded, and amended.
- 2019-05-14: MDR definitions and interpretations added
