Joint Commission official "Do Not Use" list
| Do not use | Problem | Use instead |
|---|---|---|
| U, u (unit) | Mistaken for 0, 4 or cc | Write "unit" |
| IU (international unit) | Mistaken for IV or 10 | Write "international unit" |
| Q.D., QD, q.d., qd; Q.O.D., QOD, q.o.d., qod | Mistaken for each other; period after Q mistaken for I | Write "daily" and "every other day" |
| Trailing zero (X.0 mg) | Decimal point missed: 1.0 read as 10 | Write X mg |
| Missing leading zero (.X mg) | Decimal point missed: .5 read as 5 | Write 0.X mg |
| MS, MSO4, MgSO4 | Morphine sulfate and magnesium sulfate confused | Write "morphine sulfate" or "magnesium sulfate" |
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Common abbreviations
| Abbreviation | Meaning |
|---|---|
| ac | before meals |
| pc | after meals |
| bid | twice a day |
| tid | three times a day |
| qid | four times a day |
| q4h | every 4 hours |
| prn | as needed |
| po | by mouth |
| NPO | nothing by mouth |
| stat | immediately |
| SL | sublingual (under the tongue) |
| IM | intramuscular |
| IV | intravenous |
| gtt | drop(s) |
| mL | milliliter |
| mg | milligram |
| mcg | microgram (write it out; "ug" is error-prone) |
| BP | blood pressure |
| HR | heart rate |
| RR | respiratory rate |
| SpO2 | oxygen saturation by pulse oximetry |
| I&O | intake and output |
| ADL | activities of daily living |
| ROM | range of motion |
| SOB | shortness of breath |
| NKDA | no known drug allergies |
| DNR | do not resuscitate |
| CBC | complete blood count |
| BMP | basic metabolic panel |
| EKG/ECG | electrocardiogram |
| Rx | prescription |
| OTC | over the counter |
| Hx | history |
| Dx | diagnosis |
| Tx | treatment |
| c/o | complains of |
| WNL | within normal limits |
Exam tips
- On the PTCB, sig codes (bid, tid, q4h) appear in days-supply math - practice with the pharmacy math calculator.
- If an answer choice uses a Do Not Use abbreviation as the “correct” way to write an order, it is wrong.
- Terminology roots help you decode unfamiliar terms - see medical terminology.
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Frequently asked questions
What abbreviations are on the Do Not Use list?
U, IU, Q.D., Q.O.D., trailing zeros, missing leading zeros, and MS/MSO4/MgSO4.
What does bid mean?
Twice a day (from Latin bis in die).
What does NPO mean?
Nothing by mouth.
Why is a trailing zero dangerous?
If the decimal point is missed, 1.0 mg can be read as 10 mg - a tenfold overdose.
Sources
- The Joint Commission - Do Not Use List of Abbreviations (accessed 2026-09-23)
- ISMP - List of Error-Prone Abbreviations (accessed 2026-09-23)