Common Medical Abbreviations and Meanings: OET Guide

Common Medical Abbreviations and What They Mean: A Guide for Medical Students, Clinicians and OET Candidates

A structured reference for medical students, practising clinicians and healthcare professionals preparing for the OET, with US and UK/Australian usage side by side.

Medical abbreviations are shortened forms of clinical terms, such as BID for “twice a day,” BP for “blood pressure” and CBC for “complete blood count,” used in prescriptions, charts and case notes. They save time and standardize communication, but the same letters can mean different things across specialties and countries, so every student and clinician needs to know the abbreviation, its context and its safer written-out alternative.

This guide covers the most common medical abbreviations grouped by clinical setting: prescriptions, vital signs, conditions, tests, hospital locations and documentation. It also compares US and UK/Australian conventions, flags the abbreviations that are unsafe to use, and shows how to handle abbreviations in the OET Listening, Reading, Writing and Speaking sub-tests.

Why do doctors use abbreviations?
Prescription and dosing abbreviations
Vital signs and physical exam abbreviations
Common condition and disease abbreviations
Lab test and imaging abbreviations
Hospital department and location abbreviations
Patient note and documentation abbreviations
Professional title abbreviations
US vs UK and Australian abbreviations
Abbreviations to avoid: the “Do Not Use” list
Medical abbreviations and the OET
Tips for learning medical abbreviations
Frequently asked questions

Why do doctors use abbreviations?

Clinicians write notes, orders and prescriptions many times a day. A shared shorthand speeds up documentation and lets a nurse, pharmacist and physician read the same order the same way. The trade-off is risk: an abbreviation that is clear in one specialty, hospital or country can be misread in another, which is why safety organizations publish lists of approved and discouraged abbreviations.

For medical students, abbreviations are part of reading charts, presenting patients and passing exams. For practising clinicians and international graduates, they are also a patient-safety issue and, for anyone sitting the OET, a language-accuracy issue.

Prescription and dosing abbreviations

These appear on prescriptions, pharmacy labels and medication charts. They tell you how much to take, how often and by what route.

BID: twice a day (from Latin bis in die)
TID: three times a day
QID: four times a day
PRN: as needed (from Latin pro re nata)
PO: by mouth (from Latin per os)
IV: intravenous, meaning into a vein
IM: intramuscular, meaning into a muscle
Subcut: subcutaneous, meaning under the skin (often written SC or SQ, but see the safety section below)
STAT: immediately
AC: before meals
PC: after meals
HS / QHS: at bedtime (these are discouraged in some settings; see below)
NPO: nothing by mouth (from Latin nil per os), often used before surgery
Rx: prescription
OTC: over the counter, meaning available without a prescription
mg: milligram
mcg: microgram
mL: milliliter

Vital signs and physical exam abbreviations

Vital signs are the basic measurements taken at nearly every visit.

BP: blood pressure
HR: heart rate
RR: respiratory rate (breaths per minute)
T: temperature
SpO2: oxygen saturation, the percentage of oxygen in your blood as measured by a finger sensor
BMI: body mass index, a measure based on height and weight
WNL: within normal limits
HEENT: head, eyes, ears, nose and throat
ROM: range of motion
LOC: level of consciousness (or sometimes “loss of consciousness,” depending on context)
A&O: alert and oriented, often written A&Ox3 or A&Ox4 to show how many areas of orientation the patient has (such as person, place, time and situation)
PERRLA: pupils equal, round and reactive to light and accommodation

Common condition and disease abbreviations

HTN: hypertension (high blood pressure)
DM: diabetes mellitus
T1DM / T2DM: type 1 and type 2 diabetes mellitus
CAD: coronary artery disease
MI: myocardial infarction (heart attack)
HF: heart failure (older notes may say CHF, for congestive heart failure)
AFib: atrial fibrillation, an irregular heart rhythm
CVA: cerebrovascular accident (stroke)
TIA: transient ischemic attack, sometimes called a mini-stroke
COPD: chronic obstructive pulmonary disease
URI: upper respiratory infection
UTI: urinary tract infection
GERD: gastroesophageal reflux disease
CKD: chronic kidney disease
AKI: acute kidney injury
DVT: deep vein thrombosis, a blood clot in a deep vein
PE: pulmonary embolism, a blood clot in the lungs
DKA: diabetic ketoacidosis
TB: tuberculosis
HIV: human immunodeficiency virus
SOB: shortness of breath

Lab test and imaging abbreviations

CBC: complete blood count, which measures red cells, white cells and platelets
BMP: basic metabolic panel, a group of blood chemistry tests
CMP: comprehensive metabolic panel, a BMP plus liver-related tests
LFTs: liver function tests
HbA1c (or A1c): a blood test reflecting average blood sugar over roughly the past three months
INR: international normalized ratio, a measure of how quickly blood clots, often used to monitor warfarin
ABG: arterial blood gas
UA: urinalysis
CRP: C-reactive protein, a marker of inflammation
ESR: erythrocyte sedimentation rate, another inflammation marker
ECG / EKG: electrocardiogram, a recording of the heart’s electrical activity
EEG: electroencephalogram, a recording of brain activity
CXR: chest X-ray
CT: computed tomography
MRI: magnetic resonance imaging
US: ultrasound

Hospital department and location abbreviations

ED / ER: emergency department / emergency room
ICU: intensive care unit
NICU: neonatal intensive care unit
OR: operating room
PACU: post-anesthesia care unit, where patients recover after surgery
OPD: outpatient department
L&D: labor and delivery

Patient note and documentation abbreviations

Clinical notes often follow a standard structure, so these abbreviations show up constantly.

CC: chief complaint, the main reason for the visit
HPI: history of present illness
PMH: past medical history
FH: family history
SH: social history
ROS: review of systems
H&P: history and physical
SOAP: subjective, objective, assessment, plan, a common note format
Hx: history
Dx: diagnosis
Tx: treatment
Sx: symptoms
Fx: fracture (in some contexts, “function”)
NKDA: no known drug allergies
DNR: do not resuscitate
DNI: do not intubate
AMA: against medical advice (when a patient leaves before treatment is complete)
D/C: discharge or discontinue, a famously ambiguous one that depends on context
POA: power of attorney (or “present on admission” in billing and coding)

Professional title abbreviations

MD: Doctor of Medicine
DO: Doctor of Osteopathic Medicine
RN: registered nurse
LPN / LVN: licensed practical nurse / licensed vocational nurse
NP: nurse practitioner
PA: physician assistant
CNA: certified nursing assistant
PT: physical therapist
OT: occupational therapist
RT: respiratory therapist
PharmD: Doctor of Pharmacy

US vs UK and Australian abbreviations

The same instruction is often written differently in the US and in the UK, Australia and New Zealand. Learn the variant used where you will work or sit your exam, and recognise the other.

US style	UK / Australian style	Meaning
CBC	FBC	Full or complete blood count
ER	A&E (ED is also common)	Emergency department
NPO	NBM	Nil (nothing) by mouth
BID	BD (or bd)	Twice a day
TID	TDS	Three times a day
QID	QDS	Four times a day
QHS / HS	nocte	At night
QD (discouraged)	OD (or write “once daily”)	Once a day
AFib	AF	Atrial fibrillation
BMP	U&Es (closest equivalent)	Urea, electrolytes and kidney function
OR	Theatre	Operating room
PCP	GP	Primary care doctor

Spelling and drug names differ too: edema and anemia become oedema and anaemia, ischemia becomes ischaemia, acetaminophen becomes paracetamol, epinephrine becomes adrenaline and albuterol becomes salbutamol. Note that “OD” can also be misread as overdose or right eye, so many UK guidelines prefer “once daily” written in full.

Abbreviations to avoid: the “Do Not Use” list

Some abbreviations are easy to misread and have contributed to medication errors. In the United States, The Joint Commission maintains an official “Do Not Use” list for the organizations it accredits, and the Institute for Safe Medication Practices (ISMP) publishes a longer list of error-prone abbreviations. The commonly cited items include:

U or u for “unit”: it can look like a zero or a 4. Write “unit” in full.
IU for “international unit”: it can be mistaken for IV or the number 10. Write “international unit.”
Q.D., QD, q.d., qd for “daily” and Q.O.D., QOD for “every other day”: they can be confused with each other or with QID. Write “daily” or “every other day.”
Trailing zero (for example “5.0 mg”): it can be misread as 50 mg. Write “5 mg.”
Missing leading zero (for example “.5 mg”): it can be misread as 5 mg. Write “0.5 mg.”
MS, MSO4 and MgSO4: they can be confused with each other (morphine sulfate vs. magnesium sulfate). Write each drug name in full.

The ISMP list also discourages others, such as writing “SC” or “SQ” for subcutaneous (it can be mistaken for “SL” or “5 every”) and “qhs” for nightly dosing. Rules and preferences vary by hospital and country, so always follow the policy of your own organization.

If you are a student or clinician: treat the lists above as a minimum. Follow your own hospital or country policy, write the full word whenever an abbreviation could be misread, and confirm any unclear order or note with its author before acting on it.

Medical abbreviations and the OET

The OET (Occupational English Test) assesses English for healthcare professionals, and abbreviations matter differently in each of its four sub-tests. Check the current official OET assessment criteria and sample papers for your profession, because guidance and examples are updated.

Sub-test	How abbreviations appear	What to do
Listening	Consultation notes you complete often use shorthand	Recognise common terms by ear, and check the official guidance on accepted short forms and spelling
Reading	Clinical texts and notes use abbreviations without explanation	Learn high-frequency abbreviations so you can read at speed
Writing	Case notes are shorthand; your letter must be clear for its reader	Expand shorthand into full wording, keep only standard abbreviations for a clinician reader, and use none for a patient or carer
Speaking	Role-plays with a patient or carer	Use plain language: say “high blood pressure,” not “HTN,” and explain any term the patient may not know

From case-note shorthand to written-out English

A core OET Writing skill is turning shorthand into clear sentences. Case notes in OET materials may use UK or Australian conventions, so learn those variants too.

Case-note shorthand	Written out for a letter
c/o SOB on exertion x 2/52	Complained of shortness of breath on exertion for two weeks
PMH: HTN, T2DM, IHD	Past medical history of hypertension, type 2 diabetes mellitus and ischaemic heart disease
Amlodipine 5 mg od	Amlodipine 5 mg once daily
O/E: BP 150/90, HR 88 reg, afebrile	On examination, blood pressure was 150/90 mmHg, heart rate was 88 beats per minute and regular, and the patient was afebrile
NKDA	No known drug allergies
Plan: bloods, CXR, review 1/52	Plan: blood tests and chest X-ray, with review in one week

Tips for learning medical abbreviations

Learn by category. Memorizing the dosing abbreviations together, then the lab tests, is easier than working through an alphabetical list.
Break them into word parts. Many abbreviations come from Latin or Greek roots. Knowing that per os means “by mouth” makes PO unforgettable.
Use spaced repetition. Short, frequent flashcard reviews beat long cramming sessions, especially in the weeks before an exam.
Read real documents. Practise on sample SOAP notes, discharge summaries and OET-style case notes to see abbreviations in context.
Learn both variants. If you will study, work or test across systems, learn the US and the UK/Australian forms side by side.
Practise writing them out. Convert shorthand into full sentences under timed conditions, as OET Writing requires.
Watch for ambiguity. Note the abbreviations with more than one meaning (such as D/C, POA, LOC and CA) and always check the surrounding context.
Learn the safety list early. Knowing which abbreviations to avoid is as important as knowing the common ones.

Frequently asked questions

What are the most common medical abbreviations?

Some of the most frequently used are BP (blood pressure), HR (heart rate), BID (twice daily), PRN (as needed), PO (by mouth), IV (intravenous), CBC (complete blood count), ECG or EKG (electrocardiogram), ER or ED (emergency room or department), and HTN (hypertension).

What does PRN mean on a prescription?

PRN means “as needed.” A medication marked PRN is taken only when a particular symptom occurs, such as pain or nausea, and not on a fixed schedule. The label should state the symptom and the maximum dose allowed in a day.

What is the difference between BID, TID and QID?

BID means twice a day, TID means three times a day and QID means four times a day. They describe frequency only, so the exact timing (for example, with meals or every 8 hours) should be stated separately.

What does NPO mean?

NPO means “nothing by mouth,” from the Latin nil per os. It is commonly ordered before surgery or certain tests, when eating or drinking could cause complications.

What does SOB mean in a medical chart?

In clinical notes, SOB means “shortness of breath.” It is a standard symptom term, though some organizations prefer writing it out to avoid confusion.

Do all hospitals use the same abbreviations?

No. Many abbreviations are widely shared, but each hospital, country and specialty has its own approved list. The same letters can mean different things in different settings, which is why unclear abbreviations should be confirmed with the person who wrote them.

Where can I find an official list of unsafe abbreviations?

The Joint Commission publishes its “Do Not Use” list, and the Institute for Safe Medication Practices publishes a more extensive list of error-prone abbreviations. Both are free online and updated periodically.

Can I use abbreviations in the OET Writing sub-test?

Use them sparingly. Keep only standard, widely recognised abbreviations when writing to a clinician, and write other terms out in full. When the letter is addressed to a patient, carer or non-specialist, avoid abbreviations altogether. Case notes are written in shorthand, so expanding that shorthand is part of the task. Check the current official OET assessment criteria and sample letters for your profession.

Which abbreviations should I learn first for the OET?

Start with those that appear in case notes and consultations: dosing (BD, TDS, PRN), history shorthand (PMH, c/o, O/E, Hx, Dx), common conditions (HTN, T2DM, IHD, COPD) and routine tests (FBC, U&Es, ECG, CXR). Then learn the UK and Australian variants in the comparison table above.

Are medical abbreviations different in the US and the UK?

Yes. Dosing shorthand (BD vs BID), names for the emergency department (A&E vs ER), blood tests (FBC vs CBC), spellings (oedema vs edema) and some drug names (paracetamol vs acetaminophen) all differ. Learn the variant used where you will work or sit your exam.

Key takeaways

Medical abbreviations are shorthand for clinical terms, used to save time and standardize communication.
They are easiest to learn by category: dosing, vitals, conditions, tests, departments and documentation.
Many have more than one meaning, so always read them in context.
US and UK/Australian usage differ (BID vs BD, CBC vs FBC, ER vs A&E), so learn the variant you need.
Some abbreviations are officially discouraged because they cause errors. Know the “Do Not Use” list.
For the OET, expand case-note shorthand in Writing and use plain language in Speaking.

This article is for general educational purposes only and is not medical advice or official OET guidance. Abbreviation meanings and approved lists vary by institution and country. For questions about patient care, follow your local policy and consult a qualified colleague or pharmacist.

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