What does Q12H mean on a prescription?
Q12H means every twelve hours — two doses in 24 hours, spaced half a day apart, such as 8am and 8pm.
- Means:
- every 12 hours
- From:
- quaque 12 hora
- Type:
- How often
- Also written:
- q12h, q12°, Q12H, q 12 h
What it means in practice
Q12H is the strict-interval form of BID. The difference matters most for medicines with a 12-hour duration of action, where an uneven gap would leave part of the day uncovered.
Example on a prescription
Cefuroxime 500 mg PO Q12H x 10 days
Take one 500 mg cefuroxime tablet by mouth every twelve hours for ten days — for example 8am and 8pm.
Commonly confused with
- BIDBID is twice a day, usually morning and evening. Q12H pins the gap at twelve hours.
Frequently asked questions
Is Q12H the same as twice a day?
Nearly. Both are two doses, but Q12H specifies a twelve-hour gap, whereas BID is morning and evening however those fall.
What does Q12H mean on a prescription?
Take one dose every twelve hours — two doses a day, half a day apart.
Related abbreviations
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This page explains prescription notation for general information. It is not medical advice and does not replace your prescriber or pharmacist. If a label is unclear or differs from what you were told, check with your pharmacy before taking the medicine.