On a prescription medication, what does the abbreviation b.i.d. mean?

On a prescription medication, b.i.d. means twice a day.

The abbreviation comes from the Latin bis in die, meaning “twice in a day.” It traditionally tells a patient or pharmacist that a medicine should be taken two times during the day, although the exact timing depends on the prescription and medical advice.

B.i.d. belongs to a larger group of Latin prescription abbreviations. For example, q.d. means once daily, while t.i.d. means three times daily and q.i.d. means four times daily. These abbreviations were once routine in handwritten prescriptions.

Because abbreviations can be misread, many modern medical-safety guidelines recommend writing “twice a day” in full. The answer does not mean two doses taken simultaneously; it indicates two separate dosing occasions unless a clinician gives different instructions.