P.o.

Abbreviation meaning by mouth, orally (from the Latin 'per os', by mouth). One of a number of hallowed abbreviations of Latin terms that have traditionally been used in prescriptions.

Some others: > >a.c. = before meals (from 'ante cibum', before meals) >b.i.d. = twice a day (from 'bis in die', twice a day) >gtt. = drops (from 'guttae', drops) >p.c. = after meals (from 'post cibum', after meals) >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)