Pharmacy Abbreviations & Sig Codes Glossary

Frequency and timing

How often and when a medication should be taken:

• QD / daily — once a day (see the safety note below — “QD” itself is flagged as error-prone)
• BID — twice a day
• TID — three times a day
• QID — four times a day
• Q4H, Q6H, Q8H, Q12H — every 4 / 6 / 8 / 12 hours
• QHS — every night at bedtime
• PRN — as needed
• STAT — immediately
• AC — before meals
• PC — after meals
• HS — at bedtime

Routes of administration

How a medication is given:

• PO — by mouth (orally)
• SL — sublingual (under the tongue)
• PR — per rectum (rectally)
• IV — intravenous
• IM — intramuscular
• SUBQ / SC / SQ — subcutaneous
• OD — right eye; OS — left eye; OU — both eyes
• AD — right ear; AS — left ear; AU — both ears
• Top — topical

Dosage forms and quantities

Common shorthand for what’s actually being dispensed:

• Tab — tablet
• Cap — capsule
• Sol — solution
• Susp — suspension
• Ung — ointment
• gtt(s) — drop(s)
• Disp — dispense
• Qs — quantity sufficient

Prescription and workflow shorthand

Terms you’ll see on the prescription itself or in pharmacy workflow:

• Rx — prescription
• Sig — directions for use (from the Latin “signa,” meaning “write” or “label”)
• DAW — dispense as written (no generic substitution)
• NKA / NKDA — no known allergies / no known drug allergies
• NPO — nothing by mouth

Abbreviations flagged as error-prone — know these for safety, not just for the exam

Some once-common abbreviations are now flagged by patient-safety organizations because they’ve caused real medication errors — usually by being misread as something else. The Joint Commission and ISMP (Institute for Safe Medication Practices) maintain official lists of these; a few of the most relevant:

• QD (“once daily”) — frequently misread as QID (four times daily), especially handwritten. Best practice: spell out “daily.”
• QOD (“every other day”) — frequently confused with QD or QID. Best practice: spell out “every other day.”
• Trailing zeros (e.g., “5.0 mg”) — a missed decimal point reads as 50 mg. Best practice: never use a trailing zero (write “5 mg”).
• Missing leading zeros (e.g., “.3 mg”) — a missed decimal point reads as 3 mg. Best practice: always use a leading zero (write “0.3 mg”).

You’ll likely see both the older abbreviations (they still appear in real-world prescriptions and legacy systems) and the safety guidance discouraging them — knowing both is part of understanding Patient Safety and Quality Assurance on the PTCE, not a contradiction.

What does “Sig” mean on a prescription?

It’s short for the Latin “signa” (“write” or “label”) and refers to the directions for use — how and when the patient should take the medication.

Why is “QD” considered a risky abbreviation?

It’s frequently misread as QID (four times daily), especially in handwriting, which has led to real dosing errors. The Joint Commission and ISMP recommend spelling out “daily” instead.

What’s the difference between IM and IV?

IM (intramuscular) means injected into a muscle; IV (intravenous) means administered directly into a vein.

Are these abbreviations tested on the PTCE?

Prescription interpretation and terminology show up primarily under the Order Entry and Processing and Patient Safety and Quality Assurance domains — recognizing standard sig codes and knowing which abbreviations are flagged as error-prone are both fair game.