What does BID mean on a prescription?
BID means twice a day. A medicine prescribed BID is taken two times in 24 hours, usually about 12 hours apart — typically morning and evening.
- Means:
- twice a day
- From:
- bis in die
- Type:
- How often
- Also written:
- bid, b.i.d., BID
What it means in practice
BID is Latin for bis in die, “twice in a day”. Morning and evening is the standard pattern because it splits the day evenly without needing an overnight dose. Where the 12-hour gap genuinely matters, such as some antibiotics, a prescriber may write Q12H instead.
Example on a prescription
Metformin 500 mg PO BID with meals
Take one 500 mg metformin tablet by mouth twice a day, with your morning and evening meals.
Commonly confused with
- TIDTID is three times a day. BID and TID are a single letter apart.
- Q12HQ12H means strictly every 12 hours. BID is twice a day, which in practice is slightly more flexible.
- QDQD means once a day. QD written carelessly can look like QID (four times a day).
Frequently asked questions
What times of day is BID?
Usually morning and evening, around 12 hours apart. If the medicine has to be taken with food, match it to breakfast and dinner.
Is BID the same as every 12 hours?
Close, but Q12H is stricter. Q12H means a dose every 12 hours by the clock; BID means two doses a day, normally morning and evening.
What does PO BID mean?
Take it by mouth, twice a day. PO is the route and BID is the frequency.
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.