A simple guide to the MDR definition of ‘what is a medical device?’

Have you ever heard the term ‘medical device’ from the Medical Device Regulation and wondered what it actually means? You may assume, it relates to complex machinery we often see in hospitals, but in reality, the EU MDR term ‘medical device’ blankets a wide range of items.

Some of these items are common household objects that you interact with daily. For example, did you know that a blood pressure monitor or your household thermometer are regulated as medical devices? 

By the end of this article, you’ll gain a broader understanding of what kind of products are classified as medical devices,  and the benefits and inherent risks related to these medical devices. 

The definition of a medical device 

So, what is a medical device? According to the EU Medical Device Regulation (MDR), a medical device is defined as:

any instrument, apparatus, appliance, software, implant, reagent, material or other article intended by the manufacturer to be used, alone or in combination, for human beings. 

The primary purpose of these devices is to diagnose, prevent, monitor, treat or alleviate diseases, injuries or disabilities.

The MDR also states that medical devices should be designed to achieve at least one specific medical purpose. This could be anything from controlling conception, investigating, replacing or modifying the anatomy or a physiological process, or providing information via in vitro examination of specimens derived from the human body.

Finally, the MDR also includes within its definition of a medical device, any devices specifically intended for the cleaning, disinfection, or sterilisation of devices as defined above, or of those devices used for the purpose of contraception or the prevention of sexually transmitted diseases.

The classifying process: Is it a medical device? 

In the medical device industry, medical devices are grouped into categories based on how they are meant to be used, as well as how much risk they might pose to the patient.

In Europe, the Medical Device Regulation (MDR) classifies these items into four main groups: Class I, IIa, IIb, and III. Each group represents a different level of risk, with class I being the least risky and class III being the most. 

Class I medical devices are generally quite safe to use. These items are not meant to go inside your body, or might just touch your body for a short while. Think of items like a stethoscope, a bandage or a standard surgical knife. They are not used to support life or run the risk of causing illness or harm.

Interestingly, for such items, the manufacturer can say that it meets all the necessary requirements without needing to be checked by a 3rd party.

Identifying medical devices in everyday life

Many objects that play essential roles in our everyday life are, in fact, medical devices, utilised to diagnose, monitor, prevent and treat diseases. Everything from your bandages, thermometers, to more complex inventions like MRI scanners fall within this category. 

Apart from that, certain devices like hearing aids and fitness trackers—commonly found in daily use—belong to the same group since they provide substantial health benefits and help improve the quality of life.

Even objects in the field of optics, such as contact lenses, glasses, and intraocular lenses used in cataract surgeries, are classified as medical devices. 

Benefits and risks of using medical devices 

Medical devices, while designed to improve health and save lives, can also pose certain risks. These risks can be categorised into several types, including physical harm, infection, and device malfunction.

It’s important to note that these risks are not always due to the device itself, but can be a result of misuse, improper maintenance, or manufacturing defects.

Physical harm

Physical harm can occur if a device is used incorrectly or if it malfunctions. This could include injuries from sharp components, burns from overheated devices, or internal damage from devices used inside the body.

For instance, a malfunctioning pacemaker could cause irregular heart rhythms, leading to serious health complications.


Infection is another risk associated with medical devices. This is particularly true for devices that are implanted into the body or those that come into contact with bodily fluids. If not properly sterilised, these devices can introduce bacteria or other pathogens into the body, leading to potentially serious infections.

Medical device malfunction

Device malfunction is a significant risk, particularly with complex devices. This could be due to a design flaw, manufacturing defect, or wear and tear over time. When a device malfunctions, it may not perform its intended function, potentially leading to a worsening of the patient’s condition.

Allergic or adverse reactions

Another risk is the potential for allergic reactions or adverse reactions to materials used in the device. Some people may be allergic to certain materials, such as latex or certain metals, and may experience reactions ranging from mild irritation to severe allergic reactions.

Incorrect or misleading data

Lastly, there is the risk of incorrect or misleading data from diagnostic devices. These devices, such as blood glucose monitors or home blood pressure kits, rely on accurate readings to guide treatment decisions. If these devices give incorrect readings, it could lead to inappropriate treatment, potentially causing harm.

While it’s important to note that no medical device is completely risk-free, they are generally outweighed by the benefits of using medical devices.

The Medical Device Regulation aims to minimise these risks by setting high standards for the design, manufacture, and use of these devices. This includes rigorous testing and quality control measures, as well as clear instructions for use and maintenance.

Who is responsible for ensuring that medical devices are safe? 

The responsibility for ensuring that medical devices are safe is shared among several entities. These include the manufacturers of the devices, regulatory authorities, healthcare providers, and even the patients themselves.

Medical device manufacturers

Manufacturers play a crucial role in ensuring the safety of medical devices. They are responsible for designing and producing devices that meet specific safety and performance standards.

This includes conducting extensive testing and quality control checks to ensure that the devices function as intended and do not pose any unnecessary risks to patients.

Manufacturers are also required to monitor the performance of their devices after they have been launched on the market and to report any adverse events or device malfunctions to the relevant regulatory authorities.

Regulatory authorities

Regulatory authorities, such as the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK or the Food and Drug Administration (FDA) in the US, are responsible for overseeing the safety of medical devices.

They review and approve devices before they can be marketed based on evidence provided by the manufacturers. They also monitor the post-market performance of devices, investigate reports of adverse events, and can take action to remove unsafe devices from the market.

Healthcare providers and medical professionals

Healthcare providers, including doctors, nurses, and other medical professionals, also have a role to play in ensuring the safety of medical devices.

They are responsible for using the devices correctly and for monitoring patients for any adverse reactions or complications. They are also expected to report any problems or concerns to the manufacturer and the regulatory authorities.

Patients and users

Finally, patients and users have a role to play in ensuring the safety of medical devices. They are encouraged to follow the instructions provided with the device, to report any problems or adverse reactions to their healthcare provider, and to participate in any follow-up or monitoring programmes that are recommended.

No device is completely risk-free, and it’s important for patients and healthcare providers to be aware of the potential risks and to weigh these against the potential benefits. This involves staying informed about the latest research and developments, following the manufacturer’s instructions for use, and reporting any adverse events or issues to the relevant authorities.