Key Takeaways
- Sig codes are Latin-based abbreviations that communicate dosing instructions.
- Common sig codes include: QD (daily), BID (twice daily), TID (three times daily), QID (four times daily).
- Route abbreviations specify how medication is administered: PO (by mouth), SL (sublingual), TOP (topical).
- Prescriptions must contain prescriber info, patient info, drug name, strength, quantity, sig, refills, and date.
- The DAW (Dispense As Written) code indicates whether generic substitution is permitted.
Prescription Interpretation
Quick Answer: Prescription interpretation involves reading and understanding all elements of a prescription including sig codes (dosing instructions), drug names, quantities, and prescriber directives. Mastery of common abbreviations like QD (daily), BID (twice daily), and PO (by mouth) is essential for accurate dispensing.
Pharmacy technicians must accurately interpret prescriptions to ensure patients receive the correct medication with proper instructions. This section covers the essential abbreviations, sig codes, and prescription elements you need to know.
Required Prescription Elements
Every valid prescription must contain:
| Element | Description | Example |
|---|---|---|
| Prescriber Information | Name, address, phone, DEA# (for controlled substances) | Dr. Smith, 123 Medical Way |
| Patient Information | Full name, date of birth, address | John Doe, DOB 01/15/1980 |
| Date Written | Date prescription was issued | 01/21/2026 |
| Drug Name | Brand or generic name | Lisinopril |
| Drug Strength | Dosage strength per unit | 10 mg |
| Quantity | Amount to dispense | #30 (thirty) |
| Sig (Directions) | Instructions for patient | 1 tab PO QD |
| Refills | Number of refills authorized | Refills: 5 |
| Prescriber Signature | Handwritten or electronic signature | [Signature] |
Common Sig Codes (Frequency)
| Abbreviation | Latin Origin | Meaning |
|---|---|---|
| QD or QDay | 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 |
| QHS | Quaque hora somni | At bedtime |
| QAM | Quaque ante meridiem | Every morning |
| QPM | Quaque post meridiem | Every evening |
| PRN | Pro re nata | As needed |
| AC | Ante cibum | Before meals |
| PC | Post cibum | After meals |
| STAT | Statim | Immediately |
| QOD | Quaque altera die | Every other day |
| QWK | Quaque week | Once weekly |
Safety Note: QD (once daily) and QOD (every other day) can look similar when handwritten. Many facilities now recommend writing "daily" and "every other day" to avoid confusion.
Route of Administration Abbreviations
| Abbreviation | Meaning |
|---|---|
| PO | By mouth (per os) |
| SL | Sublingual (under the tongue) |
| TOP or EXT | Topically (on the skin) |
| IM | Intramuscular injection |
| IV | Intravenous injection |
| SC or SQ or SubQ | Subcutaneous injection |
| PR | Per rectum |
| PV | Per vagina |
| INH | Inhalation |
| OU | Both eyes |
| OD | Right eye |
| OS | Left eye |
| AU | Both ears |
| AD | Right ear |
| AS | Left ear |
| NAS | Nasal |
| GT | Gastrostomy tube |
| NGT | Nasogastric tube |
Form Abbreviations
| Abbreviation | Meaning |
|---|---|
| TAB | Tablet |
| CAP | Capsule |
| SOL | Solution |
| SUSP | Suspension |
| SUPP | Suppository |
| INJ | Injection |
| GTT | Drops |
| UNG | Ointment |
| CR/CRM | Cream |
| LOT | Lotion |
| SYR | Syrup |
| ELIX | Elixir |
| MDI | Metered-dose inhaler |
| EC | Enteric-coated |
| ER/XR/LA/SR | Extended/sustained release |
DAW Codes (Dispense As Written)
DAW codes indicate whether generic substitution is allowed:
| DAW Code | Meaning |
|---|---|
| 0 | No product selection indicated (generic substitution permitted) |
| 1 | Substitution not allowed by prescriber |
| 2 | Substitution allowed - patient requested brand |
| 3 | Substitution allowed - pharmacist selected brand |
| 4 | Substitution allowed - generic not in stock |
| 5 | Substitution allowed - brand dispensed as generic |
| 6 | Override |
| 7 | Substitution not allowed - brand mandated by law |
| 8 | Substitution allowed - generic not available |
| 9 | Other |
Reading a Complete Sig
Example Prescription Sig: Lisinopril 10mg #30 Sig: i tab PO QD
Interpretation:
- i tab = 1 tablet (Roman numeral i = 1)
- PO = by mouth
- QD = once daily
- Translation: "Take one tablet by mouth once daily"
Example 2: Amoxicillin 500mg #21 Sig: i cap PO TID x 7 days
Interpretation:
- i cap = 1 capsule
- PO = by mouth
- TID = three times daily
- x 7 days = for 7 days
- Translation: "Take one capsule by mouth three times daily for 7 days"
What does the sig code "ii gtts OS TID" mean?
A prescription has DAW code 1. What does this indicate?
Which of the following sig codes indicates a medication should be taken before meals?