TID / BID / QID
Formal Definition
Timing abbreviations derived from Latin for medication dosing frequency: q.d. (quaque die) = once daily; b.i.d. (bis in die) = twice daily; t.i.d. (ter in die) = three times daily; q.i.d. (quater in die) = four times daily; these are written as "BID", "TID", "QID" (with periods optional) on prescriptions and administration records; modern EHRs and best practice guidelines increasingly favor plain language ("twice daily", "three times daily") to reduce medication errors and patient confusion, but the abbreviations remain ubiquitous in clinical documentation.
How It's Used on the Ward
"BID" (twice a day), "TID" (three times a day), "QID" (four times a day) — the rhythm of medication administration orders; usually written as part of the full order like "amoxicillin 500 mg PO TID" — when you see "TID" on a med sheet, the nurse will give it at roughly 8h intervals (sometimes 9-9-9, 6-12-6, depending on institutional scheduling).
Example
""Resident on rounds: 'Doxycycline 100 mg PO BID for 7 days for the cellulitis — start today after the first IV dose. Keflex 500 mg PO QID for 10 days is overkill for oral outpatient therapy, so we're going BID with doxycycline.' Both options cover strep and staph for skin infection; QID dosing has adherence issues.""
Clinical Context
Practical dosing schedules: BID = q12h (most commonly 9-9 or 8-8 hrs aligned with nursing shifts); TID = q8h (6-2-10 typical med pass timing, NOT 9-12-3 which would not be q8h exactly); QID = q6h (6-12-6-12). Avoid "every 8 hours around the clock" confusion — when written as q8h, doses should be given at 6, 14, 22. When written as TID with explicit "with meals," doses are breakfast-lunch-dinner. Limit on "TID/QID prescriptions": adherence drops significantly with >BID dosing — only use QID when pharmacokinetics truly require it (e.g., beta-lactams for severe infections, doxycycline for some indications, certain ophthalmic drops). Off-label use: TID ophthalmic drops create adherence problems in real-world settings. ISMP and Joint Commission strongly recommend against using these Latin abbreviations in medication orders ("do not use" list) and recommend plain language. Existing chart convention still uses them heavily.