Reference — Fundamentals
Medical Abbreviations Reference
Abbreviations are used throughout clinical documentation to communicate efficiently — but unapproved or ambiguous abbreviations are a recognized source of medication errors and miscommunication. This reference covers commonly used nursing and clinical abbreviations organized by category, plus the ISMP "Do Not Use" abbreviations that are prohibited in safe practice.
Educational use only. Approved abbreviation lists vary by institution. Always use only facility-approved abbreviations in clinical documentation. This reference is for nursing education and NCLEX preparation. 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.
Medication and Dosing Abbreviations
| Abbreviation | Meaning |
|---|---|
| PO | By mouth (per os) |
| IV | Intravenous |
| IM | Intramuscular |
| SQ / SubQ | Subcutaneous |
| SL | Sublingual |
| PRN | As needed (pro re nata) |
| STAT | Immediately |
| QD | Every day (daily) — prefer writing "daily" |
| BID | Twice daily |
| TID | Three times daily |
| QID | Four times daily |
| Q4H, Q6H, Q8H | Every 4/6/8 hours |
| mg | Milligram |
| mcg / μg | Microgram — write "mcg" not μg (easily misread) |
| mL | Milliliter |
| NPO | Nothing by mouth |
| Rx | Prescription / treatment |
Assessment and Clinical Abbreviations
| Abbreviation | Meaning |
|---|---|
| VS | Vital signs |
| BP | Blood pressure |
| HR | Heart rate |
| RR | Respiratory rate |
| SpO2 | Peripheral oxygen saturation (pulse oximetry) |
| I&O | Intake and output |
| SOB / DOE | Shortness of breath / dyspnea on exertion |
| LOC | Level of consciousness |
| A&O × 4 | Alert and oriented to person, place, time, and situation |
| N/V | Nausea and vomiting |
| c/o | Complains of / complaint of |
| WNL | Within normal limits |
| Hx / PMH | History / past medical history |
| Sx | Symptoms |
| Dx | Diagnosis |
| Tx | Treatment |
| GCS | Glasgow Coma Scale |
Lab and Diagnostic Abbreviations
| Abbreviation | Meaning |
|---|---|
| CBC | Complete blood count |
| BMP / CMP | Basic / Comprehensive metabolic panel |
| ABG | Arterial blood gas |
| BUN | Blood urea nitrogen |
| Cr / SCr | Creatinine / serum creatinine |
| INR / PT | International normalized ratio / prothrombin time |
| PTT / aPTT | Partial thromboplastin time / activated PTT |
| UA | Urinalysis |
| C&S | Culture and sensitivity |
| EKG / ECG | Electrocardiogram |
| CXR | Chest X-ray |
| U/A | Urinalysis |
Unsafe Abbreviations — Do Not Use
Patient safety warning.The following abbreviations appear on the ISMP (Institute for Safe Medication Practices) and Joint Commission "Do Not Use" lists because they have been associated with medication errors, sometimes fatal. Never use these in clinical orders or documentation.
| Unsafe Abbrev. | Intended Meaning | Risk | Use Instead |
|---|---|---|---|
| U or u | Units (as in insulin) | Misread as "0" or "4" → 10× overdose risk (e.g., "10U" read as "100") | Write "units" |
| IU | International units | Misread as "IV" or "10" → wrong route or dose | Write "international units" |
| QD | Every day (once daily) | Misread as "QID" (four times daily) → 4× intended dose | Write "daily" |
| QOD | Every other day | Misread as "QD" (daily) or "QID" (4×/day) | Write "every other day" |
| Trailing zero (1.0 mg) | 1 mg | Decimal point missed → read as "10 mg" → 10× overdose | Write "1 mg" (no trailing zero) |
| Naked decimal (.5 mg) | 0.5 mg | Decimal point missed → read as "5 mg" → 10× overdose | Write "0.5 mg" (leading zero required) |
| MS / MSO4 | Morphine sulfate | Confused with magnesium sulfate (MgSO4) → wrong drug | Write "morphine sulfate" |
| MgSO4 | Magnesium sulfate | Confused with morphine sulfate (MSO4) → wrong drug | Write "magnesium sulfate" |
| D/C | Discharge or discontinue | Ambiguous — may cause premature discontinuation of medications | Write "discharge" or "discontinue" fully |
| cc | Cubic centimeter (= mL) | Misread as "U" (units) → wrong dose | Write "mL" |
NCLEX Quick Tips
- The most dangerous unsafe abbreviations on NCLEX: "U" for units (risk of 10× insulin overdose) and trailing zeros / missing leading zeros
- Never use trailing zeros (1.0 mg) — always use leading zeros (0.5 mg)
- MS and MgSO4 should never be abbreviated — they have caused fatal errors when confused
- QD and QOD are on the "Do Not Use" list — write "daily" or "every other day" fully
- When a nurse receives an order with a "Do Not Use" abbreviation, the correct action is to clarify the order with the prescriber before administering
Related Resources
Standards & sources
Fact-checked Jun 21, 2026This page is written to align with American Nurses Association (ANA) Standards of Practice · The Joint Commission. 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 →