The instructions for use (IFU; German: Gebrauchsanweisung) are part of the user interface and provide the information required for the safe and intended use of a medical device. They are themselves subject to usability assessment: Instructions that are hard to understand cause use errors instead of preventing them.
The IFU as part of the user interface
A common misconception is to treat the instructions for use as a downstream accompanying document, separate from actual product development and often written only shortly before the project ends. According to IEC 62366-1, however, the IFU is an integral part of the user interface, on equal footing with displays, controls, and labeling.
This classification has consequences for the development process: Like any other element of the user interface, the IFU must be included in the use-related risk analysis. Safety-relevant content of the IFU must be evaluated within the usability engineering process with regard to perceptibility, comprehensibility, and support for correct use. This is typically done in formative and, where applicable, summative evaluations. Completeness of content alone is not enough.
Why the IFU does not remedy a design weakness
In the order of priority for risk control, information for safety, which includes the instructions for use, ranks last, behind inherently safe design and protective measures in the product. This order of priority is justified empirically: Warnings and instructions are demonstrably read and followed less often than assumed under time pressure, in routine situations, or under high cognitive load.
In practice, this yields a clear test criterion: If an identified use error is addressed solely by a note in the IFU although a design solution would be possible, this must be justified in the use-related risk analysis, and this justification does not always withstand critical scrutiny by a notified body (an independent conformity assessment organization under the EU MDR). The IFU complements good design; it does not replace it.
What is examined in usability tests
Because the IFU is part of the user interface, studies examine it not only for correctness of content but for actual usability. Typical questions:
- Findability: Do users find the relevant information at all when they need it, or does it remain unread before use begins?
- Comprehensibility: Is the described action interpreted correctly by the intended user group, including laypersons without professional training?
- Correct application: Do users actually carry out the described steps in the intended order and manner?
- Warnings: Are safety-relevant notices noticed at all, or do they get lost in the volume of text?
This examination is most effective when integrated into the regular formative and summative studies of overall use. Experience shows that examining the IFU in isolation, outside the real context of use, yields results that are too optimistic because participants then read the instructions more attentively than they would in the real situation.
Design principles for understandable IFU
Some principles have become established in practice: Action steps are presented in the actual order of execution, not according to the manufacturer's component or function logic. Safety-relevant notices appear at the point in the text where the relevant action takes place, not collected in a separate warnings chapter that is easily skipped. Illustrations complement text for complex manual operations, and the terminology used follows the professional language of the intended user group rather than the manufacturer's internal terminology.
For heterogeneous user groups, such as professionals and laypersons for the same product, a tiered depth of information is often useful: a concise quick start for routine use, complemented by a more detailed reference for exceptional cases and troubleshooting. A single set of instructions with the same level of detail for all target groups rarely serves everyone well.
Electronic instructions for use (eIFU)
For certain product categories and user groups, electronic provision of the instructions for use is permitted instead of enclosing them on paper. This offers advantages (easier updating, searchable content, multimedia supplements such as explanatory videos) but brings its own usability questions: Is access actually guaranteed at the moment of need, even without an internet connection or if the display device fails? Is the navigation self-explanatory for the intended user group?
The permissibility of electronic instructions for use is tied to certain user groups and product types (usually professional users or stationary devices) and mostly rules out use by laypersons in home use. This restriction should be taken into account early in product planning because it fundamentally determines the permissible forms of provision.
Regulatory reference
The MDR requires, in Annex I Chapter III, minimum content for labeling and instructions for use, including information on safe use and on foreseeable misuse, tailored to the intended purpose (intended use) and risk class of the product. As of October 2026, the EU regulation on electronic instructions for use for medical devices sets out the permissible conditions and product categories for electronic provision. Particular attention applies to information required for performing critical tasks. Changes to such safety-relevant IFU content after validation has been completed should be assessed with regard to their impact on the human factors evidence.
According to IEC 62366-1, the IFU, as a component of the user interface, must be included in the use-related risk analysis. In human factors validation, the FDA Human Factors Guidance expressly expects that it be examined whether users consult the instructions for use when needed, understand them, and implement them correctly.
The instructions for use are part of the user interface and are subject to the same usability examination as the display and controls. They complement good design but cannot replace it. Information for safety deliberately ranks last in the order of priority for risk control.
What must be examined is not only the content but the actual findability, comprehensibility, and application in the real context of use, not in an isolated reading situation.
Frequently asked questions (FAQ)
Does the IFU have to be validated?
Not as an isolated document, but as a component of the user interface. Safety-relevant information in the IFU should be examined within formative and summative human factors evaluations with regard to findability, comprehensibility, and correct application.
What is the difference between labeling and IFU?
Labeling provides information available directly on the product or its packaging (see Labeling). The IFU contains more detailed instructions for action, background information, and safety-relevant notices. Both are components of the user interface and must be consistent with each other.
Is an additional warning in the IFU enough to address a use error?
As a rule, not sufficient if a design solution would be possible. Information for safety ranks last in the order of priority for risk control because warnings are demonstrably followed less often than assumed under time pressure, in routine situations, or under high cognitive load. They complement good design but do not replace it.
Is the IFU tested separately in usability studies?
An examination integrated into regular use is the most informative, not one performed in isolation. A separate examination of the IFU often leads to results that are too optimistic because participants read the text more attentively than they would in the real situation of use.
When is an electronic instructions for use (eIFU) permitted?
Electronic provision is tied to certain product categories and user groups, mostly professional users or stationary devices. It is generally not intended for lay use in the home environment. The applicable conditions must be checked on a product-specific basis.
Should an IFU be equally detailed for all user groups?
Not necessarily. For heterogeneous user groups, a tiered depth of information has proven effective: a concise quick start for routine use, complemented by a more detailed reference for exceptional cases. Uniformly detailed instructions rarely serve all target groups equally well.
Do you want to know whether your instructions for use will really be understood and applied correctly in a critical situation? We examine the IFU as part of the entire user interface.
More about our usability engineeringSources
- IEC 62366-1:2015+AMD1:2020, Medical devices, Part 1: Application of usability engineering to medical devices
- Regulation (EU) 2017/745 on medical devices (MDR)
- FDA Guidance: Applying Human Factors and Usability Engineering to Medical Devices