adv
sid
ehs-eye-dee
adv
1
In prescriptions, an abbreviation meaning "once a day" (from Latin semel in die), used for how often a medicine should be taken.
"The label read "500mg sid" meaning one dose every day."
"The vet prescribed the tablets sid for two weeks."
How to Use Sid
Learner’s notesIn plain EnglishA medical shorthand on prescriptions meaning the medicine is taken once every day.
Common mistake
Don't confuse with "bid" (twice a day) or "tid" (three times a day) — similar-looking prescription abbreviations with different meanings.
When to use it
Used almost exclusively in clinical or veterinary prescription notes, not everyday speech.
Easily confused with
bid →
tid
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The label read "500mg _____" meaning one dose every day.