Medical>Abbreviation Medical

* a.c. = before meals (from "ante cibum," before meals)

* ad lib: use as much as one desires (from "ad libitum")

* b.i.d. = twice a day

* caps = capsules

* da or daw = dispense as written

* g (or gm or GM) = gram

* gtt. = drops (from "guttae," drops)

* h. = hour

* mg = milligram

* ml = milliliter

* p.c. = after meals (from "post cibum," after meals)

* p.o. = by mouth, orally (from "per os," by mouth)

* p.r.n. = when necessary (from "pro re nata," for an occasion that has arisen, as circumstances require, as needed)

* q.d. = once a day (from "quaque die," once a day)

* q.i.d. = four times a day (from "quater in die," 4 times a day)

* q._h.: If a medicine is to be taken every so-many hours (from "quaque," every and the "h" indicating the number of hours)

* q.h. = every hour

* q.2h. = every 2 hours

* q.3h. = every 3 hours

* q.4h. = every 4 hours

* t.i.d. = three times a day (from "ter in die," 3 times a day)

* ut dict. = as directed (from "ut dictum," as directed)

The word "prescription" also comes from the Latin "praescriptus" and is made up of "prae," before + "scribere," to write, so that prescription meant "to write before." This reflected the historic fact that a prescription had traditionally to be written before a drug could be prepared and then administered to a patient.