Sig codes
Sig codes: prescription abbreviations and meanings
58 abbreviations used in the directions on a prescription, with their meanings and Latin origins. Flagged rows are on the Joint Commission Do Not Use list or the ISMP error-prone list.
Meanings checked against at least two public references each on October 23, 2026.
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How often
Frequency abbreviations on a prescription's directions.
| Sig code | Meaning | Latin | Flag |
|---|---|---|---|
| BID | twice a day | bis in die | |
| PRN | as needed | pro re nata | |
| QID | four times a day | quater in die | |
| TID | three times a day | ter in die | |
| Q4H | every 4 hours | None | |
| Q6H | every 6 hours | None | |
| Q8H | every 8 hours | None | |
| QAM | every morning | quaque ante meridiem | |
| QD | every day | quaque die | Do Not Use (TJC) |
| QHS | every night at bedtime | quaque hora somni | |
| QOD | every other day | None | Do Not Use (TJC) |
| Q2H | every 2 hours | None | |
| Q3H | every 3 hours | None | |
| QH | every hour | quaque hora | |
| QN | every night | None | Error-prone (ISMP) |
| TIW | three times a week | None | Error-prone (ISMP) |
When
Route
How the medication goes in: by mouth, under the tongue, into the eye.
| Sig code | Meaning | Latin | Flag |
|---|---|---|---|
| NPO | nothing by mouth | nil per os | |
| PO | by mouth | per os | |
| IM | intramuscular | None | |
| IV | intravenous | None | |
| OD | right eye; once daily | oculus dexter | Error-prone (ISMP) |
| OS | left eye | oculus sinister | Error-prone (ISMP) |
| OU | each eye | oculus uterque | Error-prone (ISMP) |
| SL | sublingual | None | |
| SUBQ | subcutaneous | None | Error-prone (ISMP) |
| AD | right ear | auris dextra | Error-prone (ISMP) |
| ID | intradermal | None | |
| IN | intranasal | None | Error-prone (ISMP) |
| IT | intrathecal | None | Error-prone (ISMP) |
| IVP | intravenous pyelogram | None | |
| IVPB | intravenous piggyback | None | |
| NG | nasogastric | None | |
| TD | tetanus and diphtheria | None | |
| TOP | topical | None |
Dosage form and quantity
The form dispensed and how it is counted.
| Sig code | Meaning | Latin | Flag |
|---|---|---|---|
| CR | creatinine | None | |
| ER | extended release; estrogen receptor | None | |
| GTT | drop; glucose tolerance test; drops | gutta | |
| CAP | capsule; community-acquired pneumonia | None | |
| DPI | dry powder inhaler | None | |
| DR | delayed release | None | |
| ELIX | elixir | None | |
| MDI | metered dose inhaler | None | |
| SOL | solution | None | |
| SR | sustained release | None | |
| SUPP | suppository | None | |
| SUSP | suspension | None | |
| TAB | tablet | None | |
| XR | extended release | None |
Prescription terms
Related references
Questions
What does sig mean on a prescription?
Sig is short for the Latin signa, 'label' or 'let it be labeled'. It marks the directions the pharmacy prints on the label.
What do BID, TID, and QID mean?
BID is twice a day (bis in die), TID is three times a day (ter in die), and QID is four times a day (quater in die).
Why are QD and QOD on the Do Not Use list?
QD (every day) and QOD (every other day) have been misread as each other and as QID. The Joint Commission bars them on medication orders; ISMP suggests writing 'daily' and 'every other day'.
Does this page tell me how to take a medication?
No. It explains what the abbreviations mean. The prescriber and pharmacist give the directions for a specific prescription.