What does 'q.d.' signify when prescribed medication?

The abbreviation 'q.d.' stands for "quaque die," which is derived from Latin and translates to "once a day." This notation is commonly used in medical prescriptions to indicate that a medication should be taken once within a 24-hour period. Understanding such abbreviations is crucial in medication administration, as it helps healthcare professionals ensure that patients adhere to the prescribed dosing schedule accurately. The other options represent different dosing frequencies, but 'q.d.' specifically denotes the once-daily administration protocol.