10 Common Prescription Abbreviations Every Pharmacy Student Should Know

June 20, 2026 · 5 min read · By Rx Challenger

Prescription abbreviations can look like a foreign language. They are not. Most prescriptions draw from a few dozen Latin-origin abbreviations that repeat constantly. Master these and you will read the vast majority of scripts with confidence.

1. PO — per os (by mouth)

The single most common route abbreviation. "PO" means the medication is taken orally. You will see this on the majority of outpatient prescriptions.

2. BID — bis in die (twice daily)

Indicates a medication should be taken twice per day, typically every 12 hours for even coverage.

3. TID — ter in die (three times daily)

Three times daily. Often spaced roughly every 8 hours.

4. QID — quater in die (four times daily)

Four times daily, typically every 6 hours.

5. PRN — pro re nata (as needed)

The patient takes the medication only when symptoms appear, subject to any maximum dose limits.

6. STAT / SOS

"STAT" means immediately. "SOS" means "if necessary" — used for one-time-as-needed doses.

Other common abbreviations

OD / OS / OU — right eye / left eye / both eyes
AD / AS / AU — right ear / left ear / both ears
AM / PM — morning / evening
NPO — nothing by mouth
hs — at bedtime (hora somni)
gtt — drops (guttae)

Why abbrevi

Shortened Latin phrases let prescribers fit more information on limited space. Mistaking "OD" (right eye) for "OD" (once daily) is a real dispensing error — which is exactly why deliberate practice matters.

Practice with Rx Challenger

The fastest way to internalize these abbreviations is through daily 5-minute challenges. Download Rx Challenger free and work through prescription scenarios at your own pace.

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