Prescription Abbreviations and What They Mean

Quick answer

Prescription abbreviations are short codes on a prescription that say how often, when and how to take a medicine. BID means twice a day, TID means three times a day and QID means four times a day. PO means by mouth, and PRN means only when needed. Most come from Latin. They sit in the sig, the line that tells the pharmacy what to write on your label.

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Medical Abbreviations - Essential Clinical Shorthand

The medical abbreviations you actually see on charts, orders, and prescriptions, expanded in plain English. Covers prescription frequency and routes, chart and history shorthand, vital signs, labs and imaging, departments, and provider titles.

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How often to take it: BID, TID, QID and q6h

These codes count the doses in a day or the hours between doses. The q means every and the h means hour, so q6h means every 6 hours.

Medical Abbreviations	Pronunciation	Meaning
BID	B-I-D	Twice a day
TID	T-I-D	Three times a day
QID	Q-I-D	Four times a day
BD	B-D	Twice a day (same as BID)
TDS	T-D-S	Three times a day (same as TID)
q4h	Q-4-H	Every 4 hours
q6h	Q-6-H	Every 6 hours
q8h	Q-8-H	Every 8 hours
q12h	Q-12-H	Every 12 hours
qAM	Q-A-M	Every morning
qPM	Q-P-M	Every afternoon or evening
PRN	P-R-N	As needed
ATC	A-T-C	Around the clock
STAT	stat	Right away

When to take it: AC, PC and HS

These codes tie a dose to meals or sleep. For example, 1 tab PO TID AC reads as 1 tablet by mouth three times a day before meals.

Medical Abbreviations	Pronunciation	Meaning
AC	A-C	Before meals
PC	P-C	After meals
HS	H-S	At bedtime; can also mean half strength
noct	nokt	At night
cf	C-F	With food

How to take it: PO, SL, IM and more

The route says how the medicine gets into your body. Eye and ear codes also sit here.

Medical Abbreviations	Pronunciation	Meaning
PO	P-O	By mouth
SL	S-L	Under the tongue
PR	P-R	In the rectum
IM	I-M	Into a muscle (a shot)
IV	I-V	Into a vein
SubQ	sub-Q	Under the skin (a shot)
top	top	On the skin
gtt	G-T-T	Drops
OD, OS, OU	O-D, O-S, O-U	Right eye, left eye, both eyes
AD, AS, AU	A-D, A-S, A-U	Right ear, left ear, both ears; can be misread as eye codes

How much and what form: tab, cap, mL

These codes name the form of the medicine and the unit for each amount.

Medical Abbreviations	Pronunciation	Meaning
tab	tab	Tablet
cap	cap	Capsule
mL	M-L	Milliliter
mg	M-G	Milligram
mcg	M-C-G	Microgram, one thousandth of a milligram
tsp	T-S-P	Teaspoon
tbsp	T-B-S-P	Tablespoon
susp	susp	Suspension, a liquid you shake
supp	supp	Suppository

Other codes on a prescription: Rx, Sig, DAW

These codes sit around the directions. They tell the pharmacy what to give you and whether to repeat it.

Medical Abbreviations	Pronunciation	Meaning
Rx	R-X	Prescription
Sig	sig	The directions to write on the label
disp	disp	Dispense, or how much to give
DAW	D-A-W	Dispense as written
non rep	non rep	Do not repeat (no refills)
ud	U-D	As directed
ad lib	ad lib	Freely, as much as you like
NTE	N-T-E	Not to exceed

Codes that are easy to misread

The Institute for Safe Medication Practices (ISMP) keeps a list of abbreviations that people have misread in harmful mix-ups. It says they should never be used. You may still see them on older notes.

Medical Abbreviations	Pronunciation	Meaning
QD	Q-D	Every day; can be misread as QID
QOD	Q-O-D	Every other day; can be misread as QD or QID
U	U	Units; can be misread as 0 or 4
IU	I-U	International units; can be misread as IV or 10
SC	S-C	Under the skin; can be misread as SL
TIW	T-I-W	Three times a week; can be misread as three times a day
OD	O-D	Right eye; also used for once daily
μg	micro-G	Microgram; can be misread as mg, giving a dose 1,000 times higher
5.0 mg	five point zero	Trailing zero; can be misread as 50 mg
.5 mg	point five	No leading zero; can be misread as 5 mg

Frequently asked questions

What does BID mean in medical abbreviations?

BID means twice a day. It comes from the Latin bis in die. On a prescription, 1 tab PO BID reads as 1 tablet by mouth twice a day.

What are sig codes?

The sig is the part of a prescription that gives the directions. The word tells the pharmacy what to write on the label. Sig codes are the short forms in it, like PO, BID and PRN.

What is the difference between BID and q12h?

BID means two doses in a day. q12h means one dose every 12 hours. Both add up to two doses a day, but q12h also sets the gap between them. Ask your pharmacist if you are not sure which times to use.

Why should QD not be written?

QD means every day, but it can be misread as QID, four times a day. That is why ISMP puts it on its list of error-prone abbreviations. Writing the word daily avoids the mix-up.

Are prescription abbreviations the same as medical abbreviations?

Prescription abbreviations are one part of medical abbreviations. Charts also use short forms for tests, history and vital signs, like CBC, Hx and BP. Our full list of medical abbreviations covers those.

What should I do if I can't read my prescription?

Ask your pharmacist or the person who wrote it. This page explains what the codes mean. It is not medical advice, and it does not replace the directions on your label.

Where do these meanings come from?

We checked each one against two lists: the MedlinePlus list of common abbreviations and a prescription list from the State of Minnesota. The misread codes come from the ISMP list and an FDA page on drug errors.