What does QD stand for in dosing schedules?

• A. Once a day
• B. Twice a day
• C. Three times per day
• D. Four times per day

Answer: (A)

Dosing abbreviations come from Latin terms describing how often to take a medication. QD stands for quaque die, meaning once per day. In other words, the dose is given every 24 hours. This matches the idea of taking the medicine once daily. Other frequencies are written differently (for example, twice daily is bid, three times daily is tid, four times daily is qid), which is why only the “once per day” interpretation fits QD. A quick example: if the prescription says take one tablet qd, you take one tablet every day, at about the same time each day. Note that some clinicians prefer writing “daily” instead of qd to avoid misreadings, but the standard meaning remains once daily.