In medicine, bid refers to the frequency of daily use of a drug, i.e. twice a day. General practitioners in the issuance of medical advice and prescriptions, the need for the name of the drug, the dose of each drug, the route of the drug and the frequency of daily use of the drug labeled clearly, and bid that is commonly used in the prescription of a frequency of use of the abbreviation, refers to the meaning of the twice a day, generally in the morning and evening of each day to take two times, the two dose time interval of 12 hours or so. In addition, there are other abbreviations such as qd, tid, qid and so on, which means once a day, three times a day, four times a day, and patients should strictly comply with the frequency of medication labeled by the doctor for use.