Time Based Prescription Abbreviations

AbbreviationMeaning / Intended MeaningNotes About Confusion
acbefore meals
achsbefore meals and at bedtime
ad libfreely; as much as desired
alt. h.every other hour
am, A.M.in the morning; before noon
apbefore dinner
ATCaround the clock
bid, BIDtwice a day
BTbedtimeIn U.S., 'hs' or 'HS' is more commonly used for bedtime
h, or hr.hour
hs or HSat bedtime, hours of sleepDo not misinterpret as 'half-strength'
manein the morning
n or noct.in the night
noct. maneq.night and morning
o.d.once per dayPreferred in the UK; Can also mean "overdose" or "right eye"; better to spell out
p.r.n., prnas needed
pcafter meals
q12hevery 12 hours
qd, q1ddaily
q2hevery 2 hours
q3hevery 3 hours
q4hevery 4 hours
q6hevery 6 hours
q6PM, etcevery evening at 6 PM
q8hevery 8 hours
qamevery morning
qd, QDevery dayMistaken as q.i.d; Instead write "daily" or "every day" per Joint Commission's "Do Not Use" List of Abbreviations
qhevery hour
qhseach night at bedtimeCan be confused with "qh" meaning every hour; better to spell out
qidfour times a day
qnNightly or at bedtimeNot commonly used in U.S.; 'hs' more common for bedtime
qod, QOD, q.o.devery other dayCan be mistaken as qd (daily) or qid (four times daily); Instead spell out "every other day" per Joint Commission's "Do Not Use" List of Abbreviations
TID, t.i.d.three times a day
tid acthree times a day before meals
TIN, t.i.n.three times a night
TIW, tiw3 times a weekSpell out; can be confused with TID (three times a day)

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