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Deciphering Your Prescription

Understanding the Latin Terms Your Doctor Uses When Writing A Prescription

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Updated December 15, 2003

from Mary J. Shomon

Do you ever wonder what the nearly illegible "b.i.d." and "p.o.," "p.r.n." and the other mysterious abbreviations on your prescription actually mean?

They are mainly abbreviations for Latin terms that are still used when writing prescriptions. Here they all are, deciphered for you!

AbbreviationLatin TranslationWhat It Means
a.c. ante cibum before meals
b.i.d. bis in die twice a day
b.i.n. bis in noctus twice a night
c cum with
cap capsula capsule
d dies day
daw dispense as written (no substituting generic or brand name drugs)
gtt gutta drop
h.s. hora somni bedtime
I.M. into the muscle
I.V. into the vein
mg milligram
ml milliliter
noxt at night
O.D. oculo dextro right eye
O.S. oculo sinistro left eye
O.U. oculo utro in each eye
p.c. post cibum after meals
p.o. per os by mouth
p.r.n. pro re nata as needed
pil pilula pill
qh quaque hora every hour
q 3 h quaque 3 hora every 3 hours
qAM every morning
qd quaque die daily
q.i.d. quater in die four times a day
q.o.d every other day
s sine without
s.l. under the tongue
tab tabella tablet
t.i.d. ter in die three times a day
tsp teaspoon
tbsp tablespoon
ut dict as directed by doctor
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