Some commonly used abbreviations for the frequency of insulin dosages: * SID, also s.i.d., is a veterinary abbreviation meaning to give medication once a day. Medical professionals for humans instead use the term qd (an abbreviation for quaque die). However, that term can be easily mistaken with the term qid (an abbreviation for quarter in die), which means four times a day. * BID, also b.i.d. or BD, is a medical abbreviation for bis in die, meaning to give medication twice a day. * TID, also t.i.d., is a medical abbreviation for ter in die, meaning to give medication three times a day. * QID also q.i.d, is a medical abbreviation which means to give the medication four times a day. * PRN is a medical abbreviation for pro re nata, meaning to give medication as the situ