Sig codes
Also known as: sig abbreviations, prescription abbreviations
Sig codes are the abbreviations prescribers use to write medication directions on prescriptions. "Sig" comes from the Latin signa, meaning "write" or "label" — the sig tells the pharmacy what directions to print for the patient.
On a prescription, the sig is the section containing the directions for use. The word comes from the Latin signa ("write" or "label"), and sig codes are the shorthand abbreviations — mostly derived from Latin — that prescribers use to communicate those directions quickly. Pharmacy staff translate the codes into plain-language instructions on the patient's label.
Sig codes cover every element of the directions. Frequency codes include QD (every day), BID (twice a day), TID (three times a day), and QID (four times a day). Timing codes include AC (before meals), PC (after meals), HS (at bedtime), and PRN (as needed). Route codes include PO (by mouth), and the eye/ear sets: OD (right eye), OS (left eye), OU (both eyes), with AD, AS, and AU as the ear equivalents. So "1 tab PO BID PC" becomes "Take 1 tablet by mouth twice daily after meals."
Accurate translation is a patient-safety issue. Misreading a sig code can change a dose schedule or route entirely, which is why some error-prone abbreviations (like QD, easily confused with QID) appear on "do not use" lists and are increasingly written out instead. Pharmacy technicians are expected to translate sigs fluently and to spot ambiguous or unsafe directions during order entry.
Sig codes are among the most heavily tested topics on the Pharmacy Technician Certification Exam (PTCE). Expect questions that ask you to decode a full sig line, distinguish look-alike abbreviations, and match Latin abbreviations to their meanings.
Key takeaways
- Sig codes are prescription abbreviations, mostly from Latin, that encode a medication's directions for use.
- Frequency codes: QD (daily), BID (twice daily), TID (three times daily), QID (four times daily).
- Timing and route codes: AC (before meals), PC (after meals), HS (bedtime), PRN (as needed), PO (by mouth).
- Eye codes are OD (right), OS (left), OU (both); AD, AS, and AU are the ear equivalents.
- Error-prone abbreviations can cause dosing mistakes, and the PTCE tests sig code translation heavily.