---
title: "Health literacy"
description: "Writing for the reader who can read the words but cannot use the numbers. For most health content, that is most readers."
url: "https://opsinjs.pensievelabs.org/content/health-literacy"
source: "https://opsinjs.pensievelabs.org/content/health-literacy.md"
section: "Content & language"
kind: "content"
reviewed: "2026-09-20"
reviewer: "content"
aliases: ["health numeracy", "low literacy", "comprehension", "writing for patients"]
---
> Elements written as `` below are opsinjs documentation
> components. Their attributes are the content: the values they render are
> generated from `tokens/*.json` and `registry/catalogue.ts` and are
> published separately at https://opsinjs.pensievelabs.org/r/index.json and under the Reference
> section.
> Nothing is missing from this page. The data simply does not live in
> the prose.
## The rule [#the-rule]
**Write for a reader who understands every word and still cannot answer the
question.** Health literacy is not the same as literacy. It is the ability to
find, understand and act on health information, and its numerical part is
health numeracy, which fails far more often than the vocabulary part.
That reframes the job. Replacing "hypertension" with "high blood pressure" is
necessary and it is the easy half. The hard half is that a reader who fully
understands "your reading is 148 over 92, and the usual range is 90 to 120 over
60 to 80" may still not be able to answer *should I do something about it?*
That is the only question they opened the app to ask.
Four rules follow.
1. **Answer the question the reader has, before the one you have data for.** They
asked "am I OK?". You have a number. The sentence must bridge the two, and the
bridge is the comparison and the action, not the number.
2. **Never make the reader do arithmetic.** No mental subtraction, no percentage
of a percentage, no unit conversion, no reading a value off an axis. If a
comparison matters, write the comparison.
3. **Give the frame with the figure.** A number with no reference point is not
information. "72" is nothing; "72 bpm, which is within your usual range of 58
to 76" is an answer.
4. **Assume interruption.** Health content is read while distracted, while
frightened, on a bus, in a corridor, one-handed. Every paragraph must survive
being the only paragraph the reader gets to.
### Writing about risk [#writing-about-risk]
Risk is where numeracy fails hardest, and it has its own canonical page:
[Risk and statistics](../health/risk-and-statistics.mdx) owns the rules and the
evidence. The content-side summary is short:
* **Absolute, never relative alone.** "Increases your risk by 50%" is
uninterpretable and usually alarming out of proportion to the underlying
change. Give the two absolute figures.
* **Natural frequencies, one denominator.** "About 3 in every 100 people" beats
"3%", and both denominators in a comparison must be the same number.
* **Never a bare percentage** in a sentence a reader is meant to act on.
* **Say what the number does not cover.** A risk figure derived from a population
is not a statement about the person reading it, and the sentence must say so.
## Approved / Rejected [#approved--rejected]
Your reading was 148/92. Your usual range is around 118/76. That is higher than usual for you. One reading on its own is often not a problem. Take another in the morning.
Your reading was 148/92 mmHg (systolic/diastolic), which is 25% above your 30-day mean.
The rejected version is accurate, precise, and asks the reader to compute their
own answer from a percentage of a statistic they have never seen.
About 3 in every 100 people taking this have a headache in the first week. That means about 97 in every 100 do not.
Headache occurs in 3% of patients, with a reported confidence interval.
The figures in that pair are invented to show the *shape* of the sentence and
carry no clinical meaning. Real frequencies come from whoever owns the clinical
content in your product; a design system must never supply them.
You have logged a reading on 5 of the last 7 days.
Your logging adherence is 71%.
## Patterns [#patterns]
**The three-part answer.** Almost every health value sentence is the same shape:
> `What it was`. `How that compares`. `What to do, or that nothing is needed`.
Filled: "Your reading was 118 over 76. That is in your usual range. Nothing to
do. Your next check is on Friday."
**The comparison, written out**
> That is `higher / lower` than `your usual range`, `your average for the last 30 days` or `your reading on a named date`.
Never "above baseline", "outside parameters", "deviating from your norm".
**The frequency**
> About `n` in every `100` people `outcome`. That means about `100 − n` in every
> 100 do not.
**The unknown**
> We do not have enough readings yet to say whether this is a trend. `n` more
> readings and we will be able to show one.
**The clinical term, introduced once**
> `Plain phrase`. Your GP might call this `clinical term`.
Not the other way round. The reader's word leads; the clinical word is the
footnote, because the reader needs to recognise it on a letter, not to use it.
### Layout is part of literacy [#layout-is-part-of-literacy]
Three formatting decisions carry more comprehension weight than most word
choices: the answer is in the first line and not behind a tap; the number and its
comparison are adjacent, not in separate cards; and the action is a control, not
a sentence a reader has to convert into a plan.
There is a genuine research literature on the presentation of laboratory
results to patients. A 2024 JMIR systematic review examines presentation
formats (doi:10.2196/53993), and a 2018 study in BMC Medical Informatics and
Decision Making examines patient-portal result presentation
(doi:10.1186/s12911-018-0589-7). We cite them as the starting point for anyone
who wants to check this material rather than take it on trust. The specific
rules and sentence patterns on this page are **our synthesis and our opinion**;
they are not lifted from either paper, and we have not run our own study.
## Banned words [#banned-words]
| Banned | Why | Use instead |
| --------------------------------------------------- | ------------------------------------------------------------------- | --------------------------------------------------------- |
| baseline, parameters, norm | Clinical register for a comparison the reader owns. | your usual range, your average |
| adherence, compliance | Describes the reader as an instruction being followed. | how often you have logged |
| percentile, standard deviation, confidence interval | Not usable by most readers, and rarely necessary. | a natural frequency, or nothing |
| a bare % in an actionable sentence | Percentages of unstated denominators are the classic numeracy trap. | n in every 100 |
| mean, median | Statistical register. | average, middle value |
| trending upward, on an upward trajectory | Implies a trend that two points cannot support. | higher than last time, and say how many readings you have |
| optimal, ideal, target (unassigned) | Implies a goal nobody set with the reader. | the range your GP gave you, or delete |
## Related components [#related-components]
* **`Value`** is the number and its unit; the frame that makes it interpretable
is the caller's responsibility and this page is what that responsibility
means.
* **`RangeBar`** is the comparison made visual. It must still ship the
comparison in words, because a picture of a comparison is not a comparison
for everyone.
* **`ResultCard`** takes the three-part answer above as its content contract.
* **`Term`** introduces a clinical word once, in the reader's own sentence.
* **`TrendSparkline`** must not be shown before there are enough readings for a
trend to mean anything; the "not enough yet" sentence is on this page for a
reason.