Sig Codes (Prescription Abbreviations)
Sig codes are standardized abbreviations derived primarily from Latin used on prescriptions to communicate directions for medication use, including frequency, route, timing, and special instructions.
Exam Tip
Must know: QD (daily), BID (twice daily), TID (3x daily), QID (4x daily), PRN (as needed), PO (by mouth), HS (bedtime), AC (before meals), PC (after meals). Critical for day supply calculations on the ExCPT.
What Are Sig Codes?
Sig codes (from the Latin "signa," meaning "write" or "label") are abbreviated directions found on prescriptions that tell the pharmacy how the patient should take or use the medication. Pharmacy technicians must be fluent in sig codes to accurately process prescriptions, calculate day supply, and prepare labels.
Common Frequency Sig Codes
| Abbreviation | Latin Origin | Meaning |
|---|---|---|
| QD | quaque die | Once daily |
| BID | bis in die | Twice daily |
| TID | ter in die | Three times daily |
| QID | quater in die | Four times daily |
| Q4H | quaque 4 hora | Every 4 hours |
| Q6H | quaque 6 hora | Every 6 hours |
| Q8H | quaque 8 hora | Every 8 hours |
| Q12H | quaque 12 hora | Every 12 hours |
| PRN | pro re nata | As needed |
| QOD | quaque altera die | Every other day |
Common Route Sig Codes
| Abbreviation | Meaning |
|---|---|
| PO | By mouth (per os) |
| SL | Sublingual (under the tongue) |
| TOP | Topically |
| INH | Inhaled |
| IM | Intramuscular injection |
| IV | Intravenous injection |
| SC / SQ / SubQ | Subcutaneous injection |
| PR | Rectally (per rectum) |
| OU | Both eyes |
| OD | Right eye (oculus dexter) |
| OS | Left eye (oculus sinister) |
| AU | Both ears |
| AD | Right ear (auris dextra) |
| AS | Left ear (auris sinistra) |
Common Timing Sig Codes
| Abbreviation | Latin Origin | Meaning |
|---|---|---|
| AC | ante cibum | Before meals |
| PC | post cibum | After meals |
| HS / QHS | hora somni | At bedtime |
| STAT | statim | Immediately |
| AM | ante meridiem | Morning |
| PM | post meridiem | Evening |
Common Instruction Sig Codes
| Abbreviation | Meaning |
|---|---|
| UD / UT DICT | As directed |
| NR | No refills |
| DAW | Dispense as written |
| D/C | Discontinue |
| NKA | No known allergies |
| NKDA | No known drug allergies |
| AAA | Apply to affected area |
ISMP Do-Not-Use Abbreviations
| Abbreviation | Problem | Write Instead |
|---|---|---|
| U (unit) | Mistaken for 0 or 4 | "unit" |
| IU | Mistaken for IV | "international unit" |
| QD | Mistaken for QID | "daily" |
| QOD | Mistaken for QD | "every other day" |
| MS, MSO4, MgSO4 | Confused with each other | "morphine sulfate" or "magnesium sulfate" |
| Trailing zero (1.0) | Mistaken for 10 | "1" |
| Lack of leading zero (.5) | Mistaken for 5 | "0.5" |
Exam Alert
Sig codes are heavily tested on the ExCPT, especially in day supply calculations. Know the common abbreviations for frequency (QD, BID, TID, QID), route (PO, SL, TOP), and timing (AC, PC, HS). Also know the ISMP error-prone abbreviations.
Study This Term In
Related Terms
Pharmacy Calculations
Pharmacy calculations are the mathematical operations pharmacy technicians must perform to accurately process prescriptions, including dosage conversions, day supply calculations, concentration and dilution problems, and percentage calculations.
DAW Codes (Dispense As Written)
DAW codes are standardized numeric codes (0-9) used on pharmacy claims to indicate whether a brand-name or generic drug should be dispensed and who is requesting the specific product.
NDC Number (National Drug Code)
The NDC (National Drug Code) is a unique 10-digit, 3-segment numeric identifier assigned to each medication product in the United States, identifying the labeler, product, and package size.
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