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:
* q.d. (qd or QD) is once a day; q.d. stands for "quaque die" (which means, in Latin, once a day).
* b.i.d. (or bid or BID) is two times a day ; b.i.d. stands for "bis in die" (in Latin, twice a day).
* q.i.d. (or qid or QID) is four times a day; q.i.d. stands for "quater in die" (in Latin, 4 times a day).
* q_h: If a medicine is to be taken every so-many hours, it is written "q_h"; the "q" standing for "quaque" and the "h" indicating the number of hours. So, for example, "2 caps q4h" means "Take 2 capsules every 4 hours."
