Prescription Abbreviations Decoded: Common Medical Shorthand

Your prescription reads "1 tab PO BID pc" and you're left wondering what that means. Medical abbreviations are a language of their own, rooted in Latin and designed for brevity. Understanding them helps you take medications correctly and communicate better with healthcare providers.

Frequency Abbreviations

BID means twice daily (bis in die). TID is three times daily (ter in die). QID is four times daily (quater in die). QD means once daily (quaque die), though many doctors now write "daily" to avoid confusion with QID.

PRN means "as needed" (pro re nata). This indicates you take the medication when symptoms occur, not on a fixed schedule. Always follow the maximum daily dose limits for PRN medications.

Route of Administration

PO means by mouth (per os). This is the most common route—swallow the pill or liquid. SL means sublingual (under the tongue). The medication dissolves there and absorbs directly into bloodstream, bypassing digestion.

IM means intramuscular injection. IV is intravenous (into a vein). PR is per rectum (suppository). TOP means topical (applied to skin). Each route has specific absorption rates and effects.

Timing Instructions

AC means before meals (ante cibum). PC means after meals (post cibum). HS means at bedtime (hora somni). These timings often relate to how the medication interacts with food or when side effects are most manageable.

Q4H means every 4 hours. Q6H is every 6 hours. The "Q" stands for "quaque" (every). These strict intervals matter for maintaining consistent medication levels in your bloodstream.

Dosage Terms

Tab means tablet. Cap is capsule. Susp is suspension (liquid with particles). Sol is solution (clear liquid). Gtt means drops (guttae). Knowing the form helps you identify the right medication at the pharmacy.

mg is milligrams. mcg or μg is micrograms (1000 times smaller than milligrams). Confusing these can be dangerous—always verify the unit with your pharmacist if unclear.

Duration Instructions

x7d means for 7 days. x10d is for 10 days. Some prescriptions say "until finished" or "ongoing" for chronic medications. Completing antibiotic courses fully is crucial even if you feel better.

Refills are indicated as "Refills: 3" or "NR" (no refills). This tells you how many times you can get the prescription filled without a new doctor's order.

Special Instructions

NPO means nothing by mouth (nil per os). This is critical before surgeries or certain tests. C with a line over it means "with." S with a line over it means "without." These are less common now but appear on older prescriptions.

Sig means "label" or directions. Everything after "Sig:" tells you how to take the medication. This is what appears on your pharmacy label.

Why Abbreviations Persist

Despite efforts to reduce abbreviations (to prevent errors), they persist because they're faster to write and universally understood among medical professionals. Electronic prescribing is reducing handwritten abbreviations, but understanding them remains valuable.

When to Ask for Clarification

If you're unsure about any abbreviation, ask your pharmacist. Don't guess—medication errors can be serious. Pharmacists are trained to interpret prescriptions and explain instructions clearly.

If handwriting is illegible, pharmacists will contact the prescriber for clarification. Never take medication if you're uncertain about the instructions.