Abbreviations for Medication Use

One of the biggest problems with treating horses successfully is owner non-compliance. That means the owner doesn’t follow the veterinarian’s directions. Sometimes that might happen because the medical “shorthand” used to say how much and when medications are given isn’t understood by horse owners or managers. In this article, Bryan Waldridge, DVM, DACVIM, of Kentucky Equine Research, helps us understand the most common abbreviations.

Veterinarians often employ a shorthand of sorts when dispensing medication to clients. Provided here is a list of the most common abbreviations.

Injectible Drugs

IV–intravenous, into a vein

IM–intramuscular, in a muscle

SC or SQ–subcutaneous, under the skin

Ophthalmic (for eyes)

OD–oculus dexter, right eye

OS–oculus sinister, left eye

OU–oculus uterque, each eye or both eyes


PO–per os, by mouth


Apply to the surface of the body or skin

Frequency of Administration

Note that it is recommended and generally less confusing to order drugs to be given every so many hours (e.g., every 4 hours), rather than BID, TID, etc., which are Latin abbreviations.

QD–quaque die, every day or every 24 hours

BID–bis in die, twice a day or every 12 hours

TID–ter in die, three times a day or every 8 hours

QID–quater in die, four times a day or every 6 hours

RN–pro re nata, as needed


cc–cubic centimeter

ml–milliliter, 1/1000th of a liter

1 cc = 1 ml

Whenever there is confusion regarding a drug’s dose, route or frequency, it is very important to consult your veterinarian for clarification. Not all drugs are used at the same dose or for the same purpose in all species. Administration of some drugs by a different route or dose can be dangerous to the patient.

Information provided by Kentucky Equine Research.

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