Common Pharmacy Abbreviations and Sig Codes: Complete Guide

Why Pharmacy Abbreviations Matter

Pharmacy abbreviations and sig codes are the shorthand language used on prescriptions to communicate dosing directions. As a pharmacy technician, you will read and interpret these abbreviations dozens of times every shift. Misreading a single abbreviation can lead to dispensing errors that put patients at risk.

The PTCE frequently tests your ability to interpret prescription sig codes, making this a high-priority study topic. This comprehensive guide covers the most common abbreviations organized by category, along with important safety considerations and error-prone abbreviations to watch out for.

Frequency Abbreviations

Frequency abbreviations tell you how often a medication should be taken. These are among the most commonly used sig codes:

• QD - Once daily (every day)
• BID - Twice daily (two times a day)
• TID - Three times daily
• QID - Four times daily
• Q4H - Every 4 hours
• Q6H - Every 6 hours
• Q8H - Every 8 hours
• Q12H - Every 12 hours
• QOD - Every other day
• QHS - At bedtime (every hour of sleep)
• PRN - As needed
• STAT - Immediately
• QAM - Every morning
• QPM - Every evening
• QW or QWK - Once weekly

Note the important distinction: Q6H (every 6 hours) means the patient takes the medication around the clock at 6-hour intervals, while QID (four times daily) means four doses during waking hours. This distinction matters for proper dosing schedules.

Route of Administration Abbreviations

Route abbreviations specify how the medication should be administered:

• PO - By mouth (per os)
• SL - Sublingual (under the tongue)
• TOP - Topically (applied to the skin)
• INH - Inhalation
• IM - Intramuscular injection
• IV - Intravenous
• IVPB - Intravenous piggyback
• SC or SubQ - Subcutaneous injection
• PR - Per rectum (rectally)
• PV - Per vagina (vaginally)
• 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)
• NAS - Nasally
• NGT - Nasogastric tube
• GT - Gastrostomy tube

Dosage Form Abbreviations

• TAB - Tablet
• CAP - Capsule
• SOL - Solution
• SUSP - Suspension
• SUPP - Suppository
• CR or ER or XR or XL - Controlled release, extended release
• SR - Sustained release
• DR - Delayed release
• ODT - Orally disintegrating tablet
• GTT - Drops
• UNG - Ointment
• CRM - Cream
• LOT - Lotion
• MDI - Metered dose inhaler
• NEB - Nebulizer solution

Timing and Meal-Related Abbreviations

• AC - Before meals (ante cibum)
• PC - After meals (post cibum)
• HS - At bedtime (hora somni)
• AM - Morning
• PM - Evening/afternoon
• C or w/ - With (cum)
• S or w/o - Without (sine)

Quantity and Measurement Abbreviations

• mg - Milligrams
• mcg - Micrograms
• g or gm - Grams
• mL - Milliliters
• L - Liters
• tsp - Teaspoon (5 mL)
• tbsp - Tablespoon (15 mL)
• mEq - Milliequivalents
• i, ii, iii - Roman numerals for 1, 2, 3 (often used for quantity)
• ss - One-half
• QS - Quantity sufficient (add enough to reach desired amount)
• UD or UT DICT - As directed
• NR - No refills
• DAW - Dispense as written
• NKA - No known allergies
• NKDA - No known drug allergies

Reading a Complete Sig Code

Being able to interpret a complete sig code is essential. Here are some examples with translations:

• i tab PO BID - Take one tablet by mouth twice daily
• ii caps PO TID AC - Take two capsules by mouth three times daily before meals
• i-ii tabs PO Q4-6H PRN pain - Take one to two tablets by mouth every 4 to 6 hours as needed for pain
• ii gtts OU BID - Instill two drops in both eyes twice daily
• Apply thin layer TOP BID to affected area - Apply a thin layer topically twice daily to the affected area
• i tab SL PRN chest pain, may repeat x3 - Place one tablet under the tongue as needed for chest pain, may repeat up to three times
• 10 mL PO QHS - Take 10 milliliters by mouth at bedtime

Error-Prone Abbreviations

The Institute for Safe Medication Practices (ISMP) maintains a list of abbreviations that should not be used because they frequently lead to errors. The Joint Commission also prohibits certain abbreviations in hospital settings. Be aware of these dangerous abbreviations:

• U (for units) - Can be mistaken for 0, 4, or cc. Write "units" instead.
• IU (for international units) - Can be mistaken for IV or the number 10. Write "international units" instead.
• QD - Can be mistaken for QID. Write "daily" instead.
• QOD - Can be mistaken for QD. Write "every other day" instead.
• Trailing zero (1.0 mg) - The decimal point can be missed, reading as 10 mg. Write "1 mg" instead.
• Lack of leading zero (.5 mg) - The decimal point can be missed, reading as 5 mg. Write "0.5 mg" instead.
• MS, MSO4, MgSO4 - Can be confused between morphine sulfate and magnesium sulfate. Write the full drug name.

Study Tips for Mastering Sig Codes

• Create flashcards with the abbreviation on one side and the meaning on the other
• Practice translating complete sig codes into plain English
• When you encounter a prescription at work, mentally translate the sig before checking the label
• Pay special attention to error-prone abbreviations, as these are commonly tested on the PTCE
• Practice writing sig codes from plain English directions back into abbreviated form

Mastering pharmacy abbreviations takes practice, but they quickly become second nature. Focus on the most common abbreviations first, build your vocabulary gradually, and always prioritize patient safety by clarifying any abbreviation you are not sure about.