Why do prescriptions use Latin abbreviations?

They are a holdover from when Latin was the shared language of medicine. They survive because they are fast to write and unambiguous between professionals who know them.

Sig code list: pharmacy abbreviations and what they mean

Q: What is a sig code?

A sig code is a shorthand abbreviation a prescriber writes on a prescription to say how a medication should be taken. Most come from Latin. The pharmacy translates them into the plain-English directions printed on the label.

A sig code is the shorthand a prescriber writes to say how a medication should be taken. Most come from Latin, and the pharmacy turns them into the plain-English directions printed on the label.

Below is every sig code in the PharmSig training deck, grouped the way you meet them on the job. Over 45 sig codes in total.

Frequency

Code	Meaning
`QD`	once daily
`BID`	twice daily
`TID`	three times daily
`QID`	four times daily
`Q4H`	every 4 hours
`Q6H`	every 6 hours
`Q8H`	every 8 hours
`Q12H`	every 12 hours
`QHS`	at bedtime
`QAM`	every morning
`QPM`	every evening

Route of Administration

Code	Meaning
`PO`	by mouth
`SL`	under the tongue
`TOP`	topically
`PR`	rectally
`PV`	vaginally
`OU`	in both eyes
`OS`	in left eye
`AU`	in both ears
`AD`	in right ear
`AS`	in left ear
`INH`	inhale
`AP`	apply
`TP`	topically

Timing

Code	Meaning
`AC`	before meals
`PC`	after meals
`AM`	in the morning
`PM`	in the evening
`HS`	at bedtime

Form / Dosage

Code	Meaning
`TAB`	tablet
`CAP`	capsule
`SUPP`	suppository
`GTT`	drop
`ML`	milliliter
`TSP`	teaspoon
`TBSP`	tablespoon

Special Instructions

Code	Meaning
`PRN`	as needed
`STAT`	immediately
`UD`	as directed
`C`	with
`S`	without
`AA`	of each
`SS`	one-half

Shorthand Dosing

Code	Meaning
`1P`	inhale 1 puff
`AP`	apply
`TP`	topically

Reading a full sig

A complete sig usually stacks several codes: an amount, a form, a route, then a frequency, and sometimes a timing or condition. So 1 tab po bid pcreads as "take 1 tablet by mouth twice daily after meals".

Paste any sig into the free sig code translator and it will spell it out. No account needed.

Learning them properly

A list is useful for looking one up. It is a poor way to actually learn them, because recognising a code on a page is not the same as recalling it under pressure at a counter.

PharmSig drills them with quizzes and flashcards that track which codes you keep getting wrong and bring those back more often. There is a 7-day free trial, and you can add your own pharmacy's codes on every plan.

This page is educational and is not medical advice. Always follow the directions on your own prescription and ask your pharmacist if anything is unclear.