Pharmacy Abbreviations & Sig Codes: 159 Meanings

Updated July 11, 2026

Sig codes are the shorthand prescribers use to communicate directions, and translating them accurately is a core pharmacy technician task the PTCE tests directly. This reference lists 159 abbreviations across 5 categories, including the ISMP error-prone abbreviations you should never use on a label. When you are ready, test yourself with our free abbreviations quiz.

Reading a sig: worked example

1 tab PO BID translates as: one tablet (tab), by mouth (PO), twice a day (BID). Build the habit of translating the whole sig into plain English before you calculate anything.

Pharmacy sig codes quick reference: dosing frequencies (QD, BID, TID, QID), routes (PO, SL, IM, IV, SubQ), timing (AC, PC, HS), dosage forms, and the error-prone abbreviations to avoid (U, IU, QD, trailing zeros). — Pharmacy sig codes quick reference. Free to save or share, from ptcbquizprep.com.

Time & Frequency

Abbr.	Meaning / safety note
ad lib	freely, as much or as often as the patient wantsFrom Latin ad libitum; used when the order sets no fixed limit.
ATC	around the clockDoses are given at set intervals through the full 24 hours, day and night.
bid	twice a dayFrom bis in die; the two doses are usually spaced about 12 hours apart.
tid	three times a dayFrom ter in die; commonly spaced roughly every 8 hours during waking hours.
qid	four times a dayFrom quater in die; do not confuse with qd (daily) or qod (every other day).
q	everyPlaced before a number and time unit, as in q8h meaning every 8 hours.
qh	every hourFrom quaque hora; a number can be added, so q1h means every 1 hour.
q1h	every 1 hourThe number can be swapped, so q3h means every 3 hours.
q2h	every 2 hours
q4h	every 4 hours
q6h	every 6 hours
q8h	every 8 hours
q12h	every 12 hours
ac	before mealsFrom ante cibum; the dose is taken shortly before eating.
pc	after mealsFrom post cibum; often used to lessen stomach upset by dosing after food.
hs	at bedtimeFrom hora somni; ISMP advises writing 'bedtime' because hs is also read as half-strength.
qhs	every night at bedtimeError-prone; can be misread as qhr (every hour), so spell out 'nightly'.
prn	as neededFrom pro re nata; a good order also states the reason and a minimum interval, as in prn pain q6h.
stat	immediately, right nowFrom statim; signals a single urgent dose to be given without delay.
qam	every morningAlso written qAM; means one dose each morning.
qpm	every eveningAlso written qPM; means one dose each evening.
ud	as directedFrom ut dictum; ISMP flags it because it can be misread as 'unit dose', so spell out 'as directed'.
noct	at nightFrom nocte.
am	morning, before noonFrom ante meridiem.
pm	afternoon or eveningFrom post meridiem.
tiw	three times a weekError-prone; easily confused with three times a day, so write '3 times weekly'.
qwk	once a week
sos	one dose if neededFrom si opus sit; a single dose given only if the situation requires it.
alt h	every other hourFrom alternis horis.
tds	three times a dayFrom ter die sumendum; a UK-style order equal to tid.
qds	four times a dayFrom quater die sumendus; a UK-style order equal to qid.
x	for (a stated duration)As in 'x 10 d' meaning for 10 days; avoid the run-together form x3d, which reads as 3 doses.

Route & Dosage Form

Abbr.	Meaning / safety note
PO	by mouth, orallyFrom per os; PO or 'by mouth' is preferred because the 'os' alone can be misread as 'left eye'.
SL	under the tongue (sublingual)The tablet dissolves under the tongue and is absorbed there rather than swallowed.
buccal	between the cheek and gumSometimes shortened to BUC; the dose dissolves against the inside of the cheek.
PR	rectally, by rectumUsed for suppositories, enemas, and rectal solutions.
PV	vaginallyFrom per vagina; also written 'vag'. Used for vaginal tablets, creams, and rings.
IM	into a muscle (intramuscular)
IV	into a vein (intravenous)
IVP	intravenous pushThe dose is injected into the vein over a short, controlled time.
IVPB	intravenous piggybackA small IV bag infused through a port on an existing IV line.
subcut	under the skin (subcutaneous)ISMP prefers 'subcut'; the older forms SQ and SC are error-prone and discouraged.
ID	into the skin (intradermal)A shallow injection; can be misread as IV or IM, so 'intradermal' is safer.
IN	into the nose (intranasal)IN can be misread as IM or IV, so write 'intranasal' or NAS.
top	applied to the skin surface (topical)
TD	through the skin over time (transdermal)Describes patches that release drug slowly, as with a transdermal patch.
INH	inhaled, breathed into the lungsRefers to the inhaled route; do not confuse with isoniazid, a drug also abbreviated INH.
neb	given by nebulizerLiquid medicine is turned into a fine mist and breathed in.
AD	right earFrom auris dextra; ISMP flags ear codes because AD, AS, and AU are confused with the eye codes OD, OS, and OU.
AS	left earFrom auris sinistra; spelling out 'left ear' avoids ear and eye mix-ups.
AU	each ear, both earsFrom auris utraque.
OD	right eyeFrom oculus dexter; OD is also misread as 'once daily', so many prescribers spell out 'right eye'.
OS	left eyeFrom oculus sinister.
OU	each eye, both eyesFrom oculus uterque.
NG	through a nasogastric tubeA tube passed from the nose to the stomach used to give medicine or feeding.
tab	tablet
cap	capsule
susp	suspensionA liquid holding solid particles that settle, so it must be shaken before each dose.
sol	solutionAlso written soln; a clear liquid with the drug fully dissolved.
elix	elixirA sweet, flavored liquid that usually contains some alcohol.
syr	syrupA thick, sugary liquid base for oral medicines.
supp	suppositoryA solid dose that melts after insertion into the rectum, vagina, or urethra.
ung	ointmentFrom unguentum; a greasy, oil-based semisolid.
cr	creamAlso written crm; a water-based semisolid that rubs in more easily than an ointment.
lot	lotionA thin, pourable liquid for spreading over the skin.
gtt	drop (gtts means drops)From gutta; used for eye, ear, and nose liquids.
troche	lozenge (troche)A solid piece that dissolves slowly in the mouth.
EC	enteric-coatedA coating that lets the tablet pass the stomach and dissolve in the intestine; do not crush.
DR	delayed-releaseReleases the drug later than a plain form, often past the stomach.
ER	extended-releaseReleases the drug slowly over time; usually do not crush or chew.
XR	extended-releaseSame idea as ER; appears in brand names to signal slow release.
XL	extended-releaseAnother slow-release label; do not crush.
SR	sustained-releaseReleases the drug gradually to keep blood levels steadier.
CR	controlled-releaseDesigned to release the drug at a set, steady rate.
IR	immediate-releaseReleases the full dose right away, unlike ER, SR, or CR forms.
inj	injection
MDI	metered-dose inhalerA pressurized inhaler that delivers one measured puff per actuation.
pulv	powderFrom pulvis; a dry form that may be mixed or reconstituted before use.

Measurement & Quantity

Abbr.	Meaning / safety note
mg	milligramOne thousandth of a gram; the most common strength unit on labels.
mcg	microgramOne thousandth of a milligram; use 'mcg', never the symbol that reads as mg.
g	gramSometimes written 'gm', but plain 'g' is the preferred abbreviation.
kg	kilogramEqual to 1,000 grams; used for weight-based dosing calculations.
mL	milliliterOne thousandth of a liter; about 5 mL equals one teaspoonful.
L	liter
cc	cubic centimeterEqual to 1 mL, but ISMP flags 'cc' because it is misread as 'u' (units); use mL.
gr	grainAn old apothecary unit of about 65 mg; easily confused with 'g' for gram, so use metric units.
tsp	teaspoonfulAbout 5 mL; patients should measure with a dosing syringe or cup, not a kitchen spoon.
tbsp	tablespoonfulAbout 15 mL, equal to three teaspoonfuls.
oz	ounceA fluid ounce is about 30 mL.
lb	poundAbout 0.45 kg; weight is often converted to kilograms for dosing.
mEq	milliequivalentA unit of chemical activity used for electrolytes such as potassium.
mmol	millimoleA unit of amount used for some electrolytes and laboratory values.
IU	international unitA standardized activity unit for vitamins and biologics; write it out because IU is error-prone.
qs	a sufficient quantityFrom quantum satis; add enough of an ingredient to reach the target amount.
qs ad	add enough to make up toAdd the base until the total volume or weight stated in the order is reached.
aa	of eachFrom ana; use the same amount of each listed ingredient.
BSA	body surface areaCalculated from height and weight; used to dose many chemotherapy drugs.
dil	diluteAn instruction to thin a preparation with a stated liquid.
#	number, or dispense this manyThe # sign before a number shows the quantity to dispense, as in #30.
dr	dramAn old apothecary unit of about 5 mL; its symbol is misread as the number 3, so use metric units.
ss	one-half (apothecary)Error-prone; can be mistaken for '55', so write 'one-half' or use the fraction.

Common Drug & Term Abbreviations

Abbr.	Meaning / safety note
APAP	acetaminophenFrom N-acetyl-para-aminophenol; ISMP recommends spelling out 'acetaminophen' since APAP is not widely recognized.
ASA	aspirin (acetylsalicylic acid)
HCTZ	hydrochlorothiazideA thiazide water pill; can be confused with hydrocortisone (HCT), so the full name is safer.
KCl	potassium chlorideA potassium supplement; written as a salt to keep the meaning clear.
NTG	nitroglycerinUsed for chest pain; spelling out the full name avoids mix-ups with other drips.
MOM	milk of magnesiaA magnesium-based antacid and laxative.
NS	normal saline (0.9% sodium chloride)
D5W	dextrose 5% in waterA common IV sugar solution.
LR	lactated Ringer'sAn IV fluid that supplies several electrolytes.
TPN	total parenteral nutritionComplete IV nutrition given when the gut cannot be used.
NSAID	nonsteroidal anti-inflammatory drugIncludes ibuprofen and naproxen.
SSRI	selective serotonin reuptake inhibitorA class of antidepressants such as sertraline and fluoxetine.
SNRI	serotonin and norepinephrine reuptake inhibitorAntidepressants such as duloxetine and venlafaxine.
PPI	proton pump inhibitorLowers stomach acid; examples include omeprazole and pantoprazole.
ACEI	angiotensin-converting enzyme inhibitorBlood pressure drugs whose generic names end in -pril.
ARB	angiotensin receptor blockerBlood pressure drugs whose generic names end in -sartan.
CCB	calcium channel blockerBlood pressure and heart-rate drugs such as amlodipine and diltiazem.
BB	beta blockerHeart and blood pressure drugs whose generic names end in -olol.
ABX	antibiotics
HRT	hormone replacement therapy
Rx	prescription, or 'take'From the Latin recipe, meaning 'take'; marks a medication order.
OTC	over the counterMedicines that can be bought without a prescription.
DAW	dispense as writtenTells the pharmacy to supply the exact product ordered and not substitute a generic.
NDC	National Drug CodeA unique number identifying a drug's maker, product, and package size.
Sig	directions for the patientFrom signa; the part of the order that becomes the printed label instructions.
disp	dispenseShows how much of the drug to give the patient.
dtd	give this many dosesFrom dentur tales doses; tells the pharmacist the number of doses to prepare.
NR	no refillsAlso written non rep, from non repetatur.
NKDA	no known drug allergiesAlso seen as NKA, meaning no known allergies of any kind.
MAR	medication administration recordThe chart that documents each dose given to a patient.
DEA	Drug Enforcement AdministrationIssues the DEA number a prescriber needs to order controlled substances.
AWP	average wholesale priceA benchmark list price used in drug pricing and reimbursement.
c	withFrom cum; traditionally written as a lowercase c with a line above it.
s	withoutFrom sine; traditionally written as a lowercase s with a line above it.
BS	blood sugar (blood glucose)Also written BG; a reading used to adjust diabetes medicines.

Error-Prone: Do Not Use

Abbr.	Meaning / safety note
U or u	intended to mean 'unit'On the Joint Commission Do Not Use list; a U is misread as 0, 4, or cc, causing large overdoses. Always write 'unit'.
IU	intended to mean 'international unit'On the Do Not Use list; misread as IV or the number 10. Write 'international unit'.
QD or q.d.	intended to mean 'every day'On the Do Not Use list; the period or tail of the q looks like an i, so it reads as qid. Write 'daily'.
QOD or q.o.d.	intended to mean 'every other day'On the Do Not Use list; misread as qd or qid. Write 'every other day'.
MS	intended to mean morphine sulfateOn the Do Not Use list; confused with magnesium sulfate. Write the full drug name.
MSO4	intended to mean morphine sulfateOn the Do Not Use list; misread as magnesium sulfate. Write 'morphine sulfate'.
MgSO4	intended to mean magnesium sulfateOn the Do Not Use list; misread as morphine sulfate. Write 'magnesium sulfate'.
Trailing zero (1.0 mg)	a whole-number dose written with a needless decimal and zeroOn the Do Not Use list; if the decimal is missed, 1.0 mg reads as 10 mg. Write '1 mg'.
Naked decimal (.5 mg)	a dose below one written without a leading zeroOn the Do Not Use list; .5 mg can be read as 5 mg. Always write '0.5 mg' with a leading zero.
cc	intended to mean cubic centimeter (milliliter)A poorly written cc looks like 'u' (units); use 'mL' instead.
µg	intended to mean microgramThe micro symbol is misread as 'm', causing a 1,000-fold error; use 'mcg'.
SC or SQ	intended to mean subcutaneousSC is misread as SL (sublingual) and SQ as '5 every'; use 'subcut'.
HS	intended to mean half-strengthConfused with hs meaning bedtime; spell out 'half-strength'.
TIW	intended to mean three times a weekMisread as three times a day or twice a week; write '3 times weekly'.
D/C	intended to mean discharge or discontinueThe two meanings are opposite; spell out 'discharge' or 'discontinue'.
@	intended to mean 'at'Misread as the number 2; write the word 'at'.
> and <	intended to mean greater than and less thanThe symbols are easily flipped or misread; write 'greater than' and 'less than'.
IJ	intended to mean injectionMisread as IV or intrajugular; write 'injection'.
o.d. or OD	intended to mean once dailyAlso means right eye, so oral doses have been placed in the eye; write 'daily'.
per os	intended to mean by mouthThe 'os' is misread as 'left eye'; use 'PO' or 'by mouth'.
x3d	intended to mean for three daysThe run-together form is misread as '3 doses'; write 'for 3 days'.
ss	intended to mean one-half or sliding scaleMisread as the number 55; write 'one-half' or spell out 'sliding scale'.
AD, AS, AU	intended to mean right ear, left ear, each earThe ear codes are confused with the eye codes OD, OS, and OU; spell out the ear.

Why error-prone abbreviations matter

The Institute for Safe Medication Practices (ISMP) and the Joint Commission flag certain abbreviations as dangerous because they cause real medication errors: "U" misread as a zero, "QD" misread as "QID", and trailing zeros misread as ten-fold overdoses. The PTCE tests both what these mean and why they should be written out instead. Those items are marked in the tables above.

Keep studying

Once the codes are second nature, put them to work in a timed setting with the pharmacy abbreviations quiz or the full 90-question PTCE exam. For the bigger picture, follow our 2026 PTCB study guide and memorize the top 200 drugs list.

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