The Oxford Comma and List Punctuation in OET Writing

“The patient presented with chest pain, shortness of breath and dizziness.” Read it again. Is that two symptoms — “shortness of breath and dizziness” as one combined complaint — or three separate ones? A native English reader who knows the clinical context will probably guess right. An examiner marking your OET letter against six fixed criteria doesn’t get to guess; ambiguity like this is exactly what the Oxford comma exists to remove, and it is one of the simplest, most learnable list-punctuation rules in OET writing.

What is the Oxford comma, and why does OET writing need a house rule for it?

The Oxford comma (also called the serial comma) is the comma that sits immediately before “and” or “or” at the end of a list of three or more items. Compare:

• Without the Oxford comma: The wound was cleaned, dressed and reviewed.
• With the Oxford comma: The wound was cleaned, dressed, and reviewed.

Both sentences are grammatically correct, and in a short list of single-word actions like this one, the missing comma changes nothing. English style guides disagree on which version is “correct” — it is a genuine style choice, not a hard grammar rule, and neither OET’s official marking guidance nor the OET writing criteria names a required convention.

The reason OET writing benefits from a fixed house rule anyway has nothing to do with style preference. It has to do with what OET lists actually contain. Everyday lists tend to be short, generic nouns where meaning survives either punctuation choice. Clinical lists are built from compound phrases — a symptom with a qualifier, a test with a result, a medication with a dose — and compound items are exactly where a missing comma stops being cosmetic and starts changing what the sentence says.

Why does dropping the comma cause real ambiguity in a clinical list?

Take the sentence this article opened with: “The patient presented with chest pain, shortness of breath and dizziness.” Without the final comma, a careful reader has to pause and decide whether “shortness of breath and dizziness” is being presented as one linked symptom (breathlessness accompanied by dizziness) or as two independent symptoms in a three-item list. Add the Oxford comma and the ambiguity disappears immediately: “chest pain, shortness of breath, and dizziness” can only be read as three separate items.

This is not a hypothetical edge case invented for a grammar lesson — it is the normal shape of clinical language, because so many symptoms and findings are naturally two or three words long. A referral letter listing “nausea, abdominal pain and vomiting” has the same structural risk as the chest-pain example above. So does a discharge letter listing “reduced mobility, poor appetite and confusion” as presenting complaints in an elderly patient — is confusion linked to poor appetite, or is it a third, separate finding? The reader needs the third possibility ruled out, and the Oxford comma is what rules it out.

Does OET require the Oxford comma?

No — and it is worth being precise about what is and is not marked here. There is no rule in the six OET writing criteria that requires the Oxford comma, and an examiner is not checking your letter against a style guide to see which convention you picked. What Language actually assesses is grammatical range and accuracy, including punctuation, across the whole letter — and inconsistent, ambiguous punctuation is what gets marked down, not the absence of one specific comma.

That distinction matters because it tells you exactly what to fix. A letter that uses the Oxford comma throughout is fine. A letter that never uses it is also fine, provided no list actually becomes ambiguous as a result. The letter that loses marks is the one that punctuates lists inconsistently — Oxford comma in paragraph two, dropped in paragraph four — because that pattern reads as reduced control over mechanics, which is precisely what the Language band descriptors penalise. The safest single habit, and the one this guide recommends as a fixed house rule, is to use the Oxford comma every time you write a list of three or more items. It costs nothing when the list is unambiguous either way, and it protects you completely on the lists that would otherwise be misread.

How do you punctuate complicated lists — medications, doses, and multiple findings?

The Oxford comma solves ambiguity between the last two items in a simple list. It does not solve a different, more serious punctuation problem: a list where the individual items themselves already contain commas. This comes up constantly in OET letters because medications are almost always written as a drug name followed by a dose, and each of those pairs is naturally separated by a comma.

Ambiguous: The patient was discharged on metformin, 500mg twice daily, atorvastatin, 20mg at night, and lisinopril, 10mg once daily.

Read that sentence cold, with no clinical background, and it is genuinely unclear how many medications are listed and where each one ends. Adding an Oxford comma before “and” does not fix this — the problem is the commas doing two different jobs at once, separating drug from dose and separating one drug-and-dose pair from the next.

Clear: The patient was discharged on metformin, 500mg twice daily; atorvastatin, 20mg at night; and lisinopril, 10mg once daily.

Semicolons now do the job commas were doing badly: they separate the three medication-and-dose pairs, while the comma inside each pair is left free to do its normal job of separating the drug name from its dose. This is the same principle tested for narrative sentences in our guide to comma splices and run-on sentences — a comma can only carry one kind of separation at a time before the sentence stops being readable.

The same fix applies to any list where an item carries its own internal comma: past medical history entries with dates (“appendicectomy, 2019; tonsillectomy, childhood”), or observations paired with values (“temperature, 38.5°C; heart rate, 112 bpm; blood pressure, 90/60 mmHg”). Whenever you notice a list item that would need its own comma even standing alone, that is the signal to switch the whole list to semicolons.

A fixed house rule for list punctuation in OET letters

Two rules cover essentially every list you will write in an OET letter, and both are fast to apply in a final read-through rather than while you are still drafting:

1. Lists of simple items (single words or short phrases): use a comma between each item, and place a comma before the final “and” or “or” — the Oxford comma — every time. This is the default for symptoms, actions taken, and short recommendations.
2. Lists where any item already contains a comma (most often medication-and-dose pairs, or history-and-date pairs): replace every comma between items with a semicolon, keeping the internal comma inside each item untouched.

Applying these consistently across a whole letter is exactly the kind of mechanical control that separates a clean Language score from one that loses marks to small, repeated slips. For the wider set of punctuation rules that interact with this one — apostrophes, colons, and when a semicolon is doing more harm than good — see our full punctuation in OET writing guide, and for how Language is scored overall, our Language criterion guide breaks down the band descriptors in detail.

Where self-editing misses this

List ambiguity is a genuinely hard error to catch by re-reading your own letter, because you already know what you meant. Your eye supplies the correct grouping automatically — “shortness of breath and dizziness” reads as two symptoms to you because you are the one who wrote it, not because the punctuation on the page actually says so. That gap between what you intended and what the sentence on the page communicates to a reader with no other context is exactly what an examiner is reading for.

The free Grammar Checker is a reasonable first pass for catching some comma-splice and basic punctuation errors automatically, but list ambiguity requires a reader who can tell whether “chest pain, shortness of breath and dizziness” was meant as two symptoms or three — a judgement a mechanical checker cannot reliably make. Our OET writing correction service has reviewed more than 11,000 letters since 2014 against all six official criteria, catching exactly this kind of list ambiguity before it costs you Language or Content marks. If you’re comparing options before booking, our pricing page breaks down turnaround and pack sizes from a single letter up to full exam preparation.