Prescription abbreviations
What QDS means
on a prescription.
QDS on a prescription means four times a day. American prescriptions write it QID, from the Latin quater in die, “four times a day”. It is easy to confuse with QD, an American form for once a day that safety groups say not to use for exactly that reason.
QDS
four times a day
quater in die, Latin for “four times a day”
Also written q.d.s., QID, q.i.d.
QDS and QID
They mean the same: QDS is the British form, QID the American one.
QID and QD
The safety group ISMP lists QD (once a day) as error-prone because it has been misread as QID. If a prescription’s letters are unclear, ask the pharmacist before giving the first dose.
What QDS doesn’t say
It says how often, not how much or exactly when. The amount, the time of day and anything about food come from the rest of the prescription, the label or the pharmacist.
Setting it up in AlongWell
Choose four times of day when you add the medicine, morning, afternoon, evening and bedtime, and AlongWell reminds at each one.
Questions
What does QDS mean on a prescription?
Four times a day. QDS is the British form of QID.
Is QID the same as QD?
No. QID means four times a day and QD means once a day. Because they are easily mixed up, safety groups advise against writing QD at all.
Sources
- College of Optometrists (UK): pharmacy and drug terms, read 28 October 2026
- MedlinePlus: Some common abbreviations, read 28 October 2026
- Partial list of prescription abbreviations (mn.gov), read 28 October 2026
- ISMP List of Error-Prone Abbreviations, Symbols, and Dose Designations (2024), read 28 October 2026
This page explains what an abbreviation means. It doesn’t say how much to take or when: follow what the doctor wrote, and ask your pharmacist if any part of a prescription is unclear.
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