Reference — Pharmacology
Medication Abbreviations Reference
Medication abbreviations are a known source of misinterpretation errors. This reference covers common accepted abbreviations, the ISMP/TJC Do-Not-Use list, and safety notes for documentation and order verification.
Educational use only. Abbreviation standards vary by institution. Always clarify ambiguous abbreviations with the prescriber rather than guessing. Follow your facility's approved abbreviation list and The Joint Commission requirements. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
ISMP / TJC Do-Not-Use Abbreviations
The following abbreviations are prohibited in medication orders by The Joint Commission and ISMP due to their association with serious errors.
| Abbreviation | Intended Meaning | Misinterpretation Risk | Use Instead |
|---|---|---|---|
| U or u | Units | Read as 0 or 4 — 10U becomes 100, causing 10× overdose | Write “units” |
| IU | International units | Mistaken for IV (intravenous) or 10 | Write “international units” |
| QD or qd | Every day (once daily) | Mistaken for QID (four times daily) | Write “daily” |
| QOD or qod | Every other day | Mistaken for QD (daily) or QID | Write “every other day” |
| Trailing zero (1.0 mg) | 1 mg | Decimal missed → read as 10 mg (10× overdose) | Write “1 mg” (no trailing zero) |
| Naked decimal (.5 mg) | 0.5 mg | Decimal missed → read as 5 mg (10× overdose) | Write “0.5 mg” (leading zero) |
| MS or MSO₄ | Morphine sulfate | Confused with magnesium sulfate (MgSO₄) | Write “morphine sulfate” |
| MgSO₄ | Magnesium sulfate | Confused with morphine sulfate (MS) | Write “magnesium sulfate” |
Common Accepted Frequency Abbreviations
| Abbreviation | Meaning | Note |
|---|---|---|
| BID | Twice daily | Every 12 hours; confirm specific times with facility policy |
| TID | Three times daily | Every 8 hours |
| QID | Four times daily | Every 6 hours |
| PRN | As needed | Document reason and response for every PRN dose |
| Q4H | Every 4 hours | |
| Q6H | Every 6 hours | |
| Q8H | Every 8 hours | |
| Q12H | Every 12 hours | |
| AC | Before meals | Timing relative to meals; insulin is often ordered AC |
| PC | After meals | |
| HS | At bedtime | Some facilities prohibit HS — may be confused with “half-strength” |
| STAT | Immediately | Give within minutes of receipt; highest priority |
| NOW | Give immediately, one time | Less urgent than STAT in some systems |
Common Route Abbreviations
| Abbreviation | Meaning |
|---|---|
| PO | By mouth (oral) |
| SL | Sublingual (under the tongue) |
| IV | Intravenous |
| IVP or IV Push | Intravenous push (bolus) |
| IVPB | Intravenous piggyback (secondary infusion) |
| IM | Intramuscular |
| SQ or SubQ | Subcutaneous |
| TOP | Topical |
| OD | Right eye (oculus dexter) |
| OS | Left eye (oculus sinister) |
| OU | Both eyes (oculus uterque) |
| PR | Per rectum (rectal) |
| NG or NGT | Nasogastric tube |
| PEG | Percutaneous endoscopic gastrostomy tube |
Note: OD, OS, OU are on the ISMP's List of Error-Prone Abbreviations — many facilities require writing out “right eye,” “left eye,” or “both eyes.” Verify your facility's policy.
Related References
Standards & sources
Fact-checked Jun 20, 2026This page is written to align with Institute for Safe Medication Practices (ISMP) · FDA prescribing information · The Joint Commission — National Patient Safety Goals. It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →