Medical Definition of t.i.d. (on prescription)
t.i.d. (on prescription): Seen on a prescription, t.i.d. means three times a day. It is an abbreviation for "ter in die" which in Latin means three times a day. The abbreviation t.i.d. is sometimes written without a period either in lower-case letters as "tid" or in capital letters as "TID". 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
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