Medical Definition of q.i.d. (on prescription)
q.i.d. (on prescription): Seen on a prescription, q.i.d. (or qid) means 4 times a day (from the Latin quater in die). The abbreviation q.i.d. is also sometimes written without a period in capital letters as "QID". However it is written, it is one of a number of hallowed abbreviations of Latin terms that have been traditionally used in prescriptions to specify the frequency with which medicines should be taken.
Other examples include:
Last Editorial Review: 5/13/2016
Medical Dictionary Definitions A - Z
Search Medical Dictionary