One of the most powerful tools you have in your medical writing toolkit is sentence structure. The way you position the subject, verb and object in a sentence can dramatically change the clarity and tone of your writing.
Active voice is often recommended because it’s direct, concise and easier to read. But passive voice also has its place, especially in scientific and technical writing. The key is knowing when to use each, and how to make that choice with purpose.
Let’s look at the difference between active and passive voice, and when each one works best.
What’s the difference?
- Active voice: The subject performs the action.
- Passive voice: The subject receives the action.
Active voice example:
- The nurse administered the vaccine.
Passive voice example:
- The vaccine was administered by the nurse.
- (Or simply: The vaccine was administered.)
In active voice, the sentence is usually shorter and clearer. In passive voice, the subject (in this case, the vaccine) is placed at the start of the sentence, and the person doing the action may be omitted.
When to use active voice
In most health and medical writing for general audiences, active voice is the better choice. It creates stronger, more engaging sentences that are easier to follow, especially for readers without a medical background.
Use active voice when you want to:
- Make content clear and direct
- Highlight who is doing the action
- Keep sentences concise and readable
- Encourage patient understanding and engagement
Examples:
- The physiotherapist recommended a daily stretching routine.
- Researchers found a link between the two conditions.
- The doctor explained the treatment options clearly.
Active voice also supports plain language principles, which are essential when writing patient education materials, consumer health content or web copy.
When passive voice is acceptable (or preferable)
Passive voice can be useful, especially in scientific, academic or regulatory writing, where the focus is often on the process or result, rather than the person performing the action.
Use passive voice when:
- The actor is unknown or irrelevant (e.g. The cause of the condition is not yet known.)
- The action itself is more important than who did it (e.g. Informed consent was obtained.)
- You need to sound objective or formal (e.g. Data were collected over a 12-month period.)
- You are delivering bad news or news that your reader may feel hostile about (e.g. The bill has not been paid for several months.)
- You’re following conventions in certain publication types, like clinical trial reports or regulatory documents.
Examples:
- The medication was administered twice daily.
- Blood samples were collected at baseline and follow-up.
- The procedure was well tolerated.
That said, even in formal documents, too much passive voice can make writing feel dull or vague. Overuse may also hide responsibility, something that can reduce trust in health communication.
Striking the right balance
Good medical writers use both voices strategically. Active voice helps with clarity, engagement and plain language. Passive voice adds formality and can help shift focus when needed.
Try this approach:
- Use active voice as your default, especially for blogs, web content and patient education.
- Use passive voice sparingly, when it adds value or meets the expectations of the audience and format.
- Always revise for clarity; whether a sentence is active or passive, it should be easy to understand.
The final word
When editing, read your sentences aloud. If a passive sentence feels long, vague or awkward, try rewriting it in active voice. You’ll often find the message becomes much stronger.
