Who this is for
The reader of a consumer health screen is anxious, distracted, on a phone, and has not seen the unit before. Every rule in this section follows from that.
What this means
The audience for this section is a person without clinical training who is reading their own result, on their own device, with nobody beside them to ask. Every rule in the health pillar is a consequence of that reader's conditions rather than of a general usability principle, which is why the conditions are stated here rather than assumed.
The same screen is read by that person under two sets of conditions, and both sets are the design target. The device is the same in both: a four-year-old Android with the screen brightness turned down and the system font size turned up two steps, settings that belong to the reader rather than to their fluency with the metric.
| Reader | What they are doing | Reading window | What the screen must give them |
|---|---|---|---|
| The first-encounter reader. This reader is not a clinician and has never encountered the unit the number is printed in. | They have opened the app because a notification said a result is ready, and they are standing up on a bus, having waited six days for it and not slept well because of the wait. | Three to fifteen seconds. | What the measurement is, in words they already hold, then the number, the scale it sits on, and what to do next. |
| The returning reader. This is the same person six months later, reading a number they now understand well. | They check the figure inside a routine they have built, and they want the figure and nothing else. | Shorter, and spent on the value rather than on the explanation. | The figure, reachable without reading through the explanatory layer. |
What the first-encounter reader takes from the screen inside those three to fifteen seconds is what they retain, what they relay to their family, and what they may act on.
The constraint that follows is that one screen serves the first-encounter reader without delaying or condescending to the returning one.
The rule
Design for a reader who is anxious, interrupted, unfamiliar with the vocabulary, and using assistive or adaptive settings, and let the fluent reader skip ahead rather than making the anxious reader catch up.
Five commitments follow from that rule. Each is an obligation on the screen, and the last column names where the commitment becomes a hard constraint elsewhere in this section.
| # | Commitment | Which reader it protects | Where it becomes a hard constraint |
|---|---|---|---|
| 1 | No unexplained jargon on a first encounter. Any clinical term appearing in a user-facing string carries a plain-English expansion in place, on the same screen. | The first-encounter reader, who does not hold the vocabulary. | Term, and the glossary at Plain-English A to Z. |
| 2 | A value is rendered with its scale, its unit and a sentence saying what it means. A value presented without those three cannot be interpreted by a reader who does not already know the metric. | The first-encounter reader, who has no prior figure to compare it against. | Reference ranges. |
| 3 | The layout survives the reader's own settings. The largest system text size, reduced motion, reduced transparency, increased contrast and greyscale are treated as the expected case for this audience rather than as an edge case, because this audience includes readers who already run those settings on every app they use. | Both readers, whose settings persist across every visit. | |
| 4 | Nothing important is carried once, quickly, or in a single channel. A reader who looks away mid-animation, cannot distinguish two hues, or has the sound off still receives the message. | The interrupted reader, and any reader whose channel is unavailable. | |
| 5 | A result is structured to be scanned rather than read in order. The sequence is the value, its meaning, and what to do now, in preference to a paragraph that has to be read from the start. | Both readers; the returning reader stops at the value, and the first-encounter reader carries on to the meaning and the next step. |
The last column is empty for commitments 3, 4 and 5 because this page names no destination for them.
Why (evidence)
Applying it
Do
Clinical
Plain English
Lead with what it is, in words the reader already owns, then give the number and the scale it sits on.
Don’t
Print HbA1c 52 and rely on a tooltip. A tooltip is not available to a
reader on a touch device who does not know there is something to tap, and it
is not read out in the flow of the sentence.
Do
Assume the system font size is set two or three steps above default, and test at 200%. Text resizing and zoom describes the check.
Don’t
Fix the height of a card that contains a clinical sentence. The sentence is the part that must not be truncated, and it is the first thing a fixed height clips.
Do
Write the "what do I do now" line even when the answer is "nothing". "No action needed. Your next test is due in March." states both the next step and the date it falls due.
Don’t
Leave a result with no next step. A reader given no answer to "so what?" supplies one, and what they supply is shaped by how the result made them feel rather than by the clinical picture.
Components that implement this
The audience model is the reason these components have the shape they do: a
result is never a bare number, a term is never left unexpanded, and a card that
carries clinical meaning has a slot for the next step whether or not the
implementing team fills it. Each of them carries status: shipped in the
catalogue, which means the component exists and its API may still change.
What this does not cover
- Clinician readers. A clinician wants density, absolute values, trends and no reassurance, which is a different surface from the one this section governs; it is covered in Sharing with a clinician.
- Children as the primary reader. A child reading their own result, and a parent or carer reading on someone else's behalf, are separate questions. Both change consent, tone and vocabulary in ways this system does not yet model.
- Reading level measurement and the wording itself. The canonical guidance for plain language lives in Plain-English A to Z and Health literacy; this page describes the reader, not the sentence.
- Localisation and translation. Translating a status word without moving it on the status axis is covered in Internationalisation.
Updates to this page
Last read through against the system on 2026-09-02. Due for review every 6 months; expiry is reported by pnpm run check:freshness.
Overview
What makes opsinjs a health design system rather than a general-purpose component library, and which decisions it fixes on a product's behalf.
Clinical interaction guidelines
Ten rules for any interface that shows someone their own health data. Each rule is written as a prohibition a reviewer can test against a rendered screen.