# Veterinary Prescription Abbreviations: SID, BID, TID, QID, PO, SC, IM, IV and More

> Veterinary prescription abbreviations explained — dosing frequency (SID, BID, TID, QID, q, EOD, PRN), routes (PO, SC, IM, IV, IP, ID, IN), eyes and ears (OD, OS, OU, AD, AS, AU) — with error-prone forms flagged.

- Source page: https://wevet.in/vet-abbreviations/prescription-abbreviations/
- Type: Abbreviations
- Publisher: WeVet
- Updated: 2026-11-01
- Audience: veterinarians and veterinary students

Abbreviations for dosing frequency, routes of administration and the eye or ear to treat, as defined in the University of Michigan list of accepted veterinary shorthand [2] and the University of Illinois Veterinary Medicine Library guide [1]. Abbreviations that the Institute for Safe Medication Practices lists as error-prone are flagged with its recommended wording [4].

## Prescription and route abbreviations

| Abbreviation | Meaning | Caution |
|---|---|---|
| SID | Once per day [2] |  |
| BID / b.i.d. | Twice a day — Latin *bis in die* [1][2] |  |
| TID / t.i.d. | Three times a day — Latin *ter in die* [1][2] |  |
| QID / q.i.d. | Four times a day — Latin *quater in die* [1][2] |  |
| q | Every, each — Latin *quaque*; e.g. qh every hour, q4h every four hours [1][2] |  |
| q.d. | Every day — Latin *quaque die* [1] | ISMP: mistaken as q.i.d.; write "daily" [4]. |
| EOD / qod | Every other day [1][2] | ISMP: qod is mistaken as qd (daily) or qid (four times daily); write "every other day" [4]. |
| PRN | As needed — Latin *pro re nata* [1][2] |  |
| ad lib | Ad libitum, as much as desired [1]; available at all times [2] |  |
| pc | After meals — Latin *post cibum / cibos* [1] |  |
| NPO | Nothing by mouth — Latin *nil per os* [1][2] |  |
| PO | By mouth — Latin *per os* [1][2] |  |
| SC / SQ | Subcutaneous(ly) [1][2] | ISMP: SC is mistaken as SL (sublingual), SQ as "5 every", and the q in sub q as "every"; write SUBQ (capitals, no spaces or periods) or subcutaneous(ly) [4]. |
| IM | Intramuscular [1][2] |  |
| IV | Intravenous [1][2] |  |
| IP | Intraperitoneal [1][2] |  |
| ID | Intradermal [1][2] |  |
| IN | Intranasal [1][2] | ISMP: mistaken as IM or IV; write "intranasal" [4]. |
| IC | Intracardiac [1][2] | Also infectious coryza in poultry [1]. |
| CRI | Constant-rate infusion [3] |  |
| NSAID | Nonsteroidal anti-inflammatory drug(s) [1][3] |  |
| OTC | Over the counter [3] |  |
| Rx | Latin *recipe*, take — used to indicate a prescription or treatment [1] |  |
| Tx | Treatment [2] |  |
| D/C | Discontinue [2] | ISMP: D/C can mean discharge or discontinue and is misread; write the word [4]. |
| OD | Right eye — Latin *oculus dexter* [1][2] | ISMP: OD, OS, OU are mistaken as AD, AS, AU; write right eye, left eye or each eye [4]. |
| OS | Left eye — Latin *oculus sinister* [1][2] |  |
| OU | Both eyes [2] |  |
| AD | Right ear [2] | ISMP: AD, AS, AU are mistaken as OD, OS, OU; write right ear, left ear or each ear [4]. AD also stands for Aleutian disease [1]. |
| AS | Left ear [2] |  |
| AU | Both ears [2] |  |

## Frequently asked questions

### What does SID mean on a veterinary prescription?

SID means once per day [2]; BID is twice a day, TID three times a day and QID four times a day [1][2].

### What is the difference between EOD and q.d.?

EOD (qod) means every other day [1][2], while q.d. means every day [1]. ISMP lists both qd and qod as error-prone and recommends writing "daily" or "every other day" [4].

### Why should OD and AD be avoided?

ISMP reports that OD, OS and OU are mistaken for AD, AS and AU and vice versa, and recommends writing right eye, left eye, each eye, right ear, left ear or each ear [4].

## References

[1] Veterinary Abbreviations & Acronyms Guide — University of Illinois — Veterinary Medicine Library. https://www.library.illinois.edu/vex/vetabbrev
[2] Accepted Veterinary Medical Shorthand and Acronyms — University of Michigan research website (az.research.umich.edu) (last updated 2016). https://az.research.umich.edu/sites/default/files/media/embedded/Accepted%20Veterinary%20Medical%20Shorthand%20and%20Acronyms.pdf
[3] Abbreviations — Merck Veterinary Manual. https://www.merckvetmanual.com/resourcespages/abbreviations
[4] ISMP List of Error-Prone Abbreviations, Symbols, and Dose Designations — Institute for Safe Medication Practices (ISMP) (2024). https://online.ecri.org/hubfs/ISMP/Resources/ISMP_ErrorProneAbbreviation_List.pdf

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Numbers in [brackets] cite the references above. For veterinary professionals. Information supports — never replaces — clinical judgement; always check the current product label and local regulations.
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