QD Means Once Daily
QD is a prescription abbreviation that stands for "once daily" or "every day," derived from the Latin phrase "quaque die." This dosing instruction indicates that a medication should be taken one time per 24-hour period.
Clinical Context and Usage
The abbreviation QD appears consistently throughout medical literature and prescribing guidelines to denote once-daily dosing schedules. Multiple high-quality guidelines demonstrate this standard usage:
- Cardiovascular medications: Rivaroxaban is prescribed as "20 mg QD with the evening meal" for atrial fibrillation 1
- Infectious disease treatment: Folinic acid dosing is specified as "10–20 mg/day PO QD" in congenital toxoplasmosis protocols 2
- Antimicrobial therapy: Daptomycin is administered as "6 mg/kg/day IV QD" for MRSA infections 3
- Respiratory medications: Montelukast is given as "10 mg qhs" (once daily at bedtime) for asthma management 4
Important Safety Considerations
QD is on the "Do Not Use" list by many safety organizations because it can be easily confused with:
- QOD (every other day)
- QID (four times daily)
These look-alike abbreviations have led to medication errors. Best practice is to write out "daily" or "once daily" instead of using the abbreviation QD.
Comparison with Other Dosing Frequencies
Understanding QD in context with other common abbreviations:
- BID = twice daily (bis in die)
- TID = three times daily (ter in die)
- QID = four times daily (quater in die)
- QOD = every other day
Research demonstrates that QD dosing typically improves medication adherence compared to more frequent dosing schedules, with one large study showing 13.6% better adherence with once-daily versus twice-daily regimens 5.