P
After
a.c.
Before meals
p.c.
After meals
A.m
Before noon
P.M.
Afternoon
h
Hourly
q.h
Every hour
h.s.
Bed time
q.d
Everyday
q.o.d
Every other day
b.i.d
Twice a day
t.i.d
Three times a day
a
Before
p.r.n
As needed
q.2h.
Every two hours
q.3h
Every three hours
q4h
Every 4 hours
q.4h prn
Every four hours as needed
N.p.o
Nothing by mouth
OD
Right eye
OS
Left eye
OU
Both eyes
p.o.
By mouth
Gtt
Drops