b.i.d. (on prescription)

b.i.d. means twice (two times) a day. It is an abbreviation for "bis in die" which in Latin means twice a day. The abbreviation b.i.d. is sometimes written without a period either in lower-case letters as "bid" or in capital letters as "BID". 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.