PTCB Sig Codes: 113-Entry Study List + 30 Practice Questions

Here are 113 study entries covering sig codes and related prescription abbreviations for PTCE preparation, grouped by what they do, with risky forms flagged. PTCB's exam outline names sig codes (with b.i.d., t.i.d., and Roman numerals as examples) but doesn't publish an official master list, so 113 is this page's study scope, not a PTCB-required count. Every meaning is tied to a named source.

Flags: Read = included here for recognition and not specifically flagged in the cited safety source for this form. ⚠ Read, don't write = the row contains an error-prone or ambiguous form that should be written more clearly; read the note for the preferred wording. ⛔ Do Not Use = ISMP marks the form as also appearing on The Joint Commission's Do Not Use list. Numbers in the Source column match the source list at the bottom.

By Castleport Test Prep Editorial Team · Last verified September 24, 2026

The sig code list

Frequency and timing

31 entries

Frequency and timing
Code	Meaning	Latin root	Flag	Note	Source
bid, b.i.d., BID	twice a day	bis in die	Read	Named in PTCB's outline (4.1).	1, 6, 7
tid, t.i.d., TID	three times a day	ter in die	Read	Named in PTCB's outline (4.1).	1, 6, 7
qid, q.i.d., QID	four times a day	quater in die	Read		6, 7
prn, p.r.n., PRN	as needed	pro re nata	Read	Usually followed by the reason: prn pain.	6, 7
ac, a.c.	before meals	ante cibum	Read		6, 7
pc, p.c.	after meals	post cibum	Read		6, 7
ac & hs, achs	before meals and at bedtime	ante cibum et hora somni	⚠ Read, don't write	Recognize the meaning, but ISMP now says not to use HS for bedtime; write the directions in words. With 3 meals, this means 4 doses a day.	3, 6
q	every; per	quaque	Read	Builds intervals: q4h, q12h.	7
qd, q.d., QD	every day (daily)	quaque die	⛔ Do Not Use	Misread as qid. Write "daily."	2, 6, 7
qod, q.o.d., QOD	every other day	quaque altera die	⛔ Do Not Use	Misread as qd or qid. Write "every other day."	2, 6
qh	every hour	quaque hora	Read		6
q4h, q6h, q8h, q12h	every 4, 6, 8, or 12 hours		Read	A gap between doses, not a count of doses.	6, 7
q4-6h	every 4 to 6 hours		Read	Ranges follow the same pattern.	7
qam, q.a.m.	every morning		Read		6, 7
qpm, q.p.m.	every evening		Read		7
hs, h.s., HS	at bedtime	hora somni	⚠ Read, don't write	ISMP's 2024 update says not to use HS for bedtime; use QHS or qhs. Lowercase hs can also be read as half-strength.	3, 6, 8
qhs, QHS	every night at bedtime	quaque hora somni	Read	ISMP's preferred bedtime form. The risky version is mixed-case "Qhs," which gets read as every hour.	2, 3, 7
qn	nightly	quaque nocte	⚠ Read, don't write	Misread as qh (every hour). Use QHS or qhs.	2, 8
stat	immediately	statim	Read		6, 7
ATC	around the clock		Read		7
tiw	three times a week		⚠ Read, don't write	Misread as three times a day. Write "3 times weekly."	2, 5
biw	twice a week		⚠ Read, don't write	Misread as twice a day. Write "2 times weekly."	2
q.w., QWK	every week		Read		7, 8
ud, u.d., ut dict	as directed	ut dictum	⚠ Read, don't write	Misread as "unit dose." Write "as directed."	2, 7
TAD	take as directed		Read		7
c̄	with	cum	Read	Written with a bar over the c.	6, 7
s̄	without	sine	Read	Written with a bar over the s.	6, 7
w/f	with food; with meals		Read		7
w/o	without		Read		7
x	times; for (x7d = for 7 days)		Read	ISMP flags "x1": it can mean one dose or for 1 day.	2, 8
max, NTE	maximum; not to exceed		Read	As in "max 3 doses" or "NTE 8 tabs/day."	7, 8

Route and site

21 entries

Memory hook: O = oculus = eye. A = auris = ear. D = dexter (right), S = sinister (left), U = uterque (each).

Route and site
Code	Meaning	Latin root	Flag	Note	Source
po, p.o., PO	by mouth	per os	Read	PO is fine. ISMP flags the spelled-out "per os," because os can be read as left eye.	2, 6, 7
SL	under the tongue (sublingual)	sub lingua	Read		6, 7
bucc	inside the cheek (buccal)	bucca	Read		7
pr, PR	rectally	per rectum	Read		6, 7
pv, PV	vaginally	per vaginam	Read		6, 7
top	topically (on the skin)		Read		6, 7
inh	by inhalation		Read		7
neb	by nebulizer		Read		6, 7
IM	into a muscle (intramuscular)		Read		6, 7
IV	into a vein (intravenous)		Read	Same letters as the Roman numeral iv (4). If context doesn't settle it, ask.	6, 7
SUBQ, subcut (also SC, SQ, sub q)	under the skin (subcutaneous)		⚠ Read, don't write	The warning applies to SC, SQ, and sub q. ISMP prefers SUBQ or the full word subcutaneous.	2, 7
ID	into the skin (intradermal)		Read		7
IN (also NAS)	intranasal		⚠ Read, don't write	IN gets read as IM or IV, and ISMP's 2024 update also retired NAS. Write "intranasal."	2, 3, 6
OD	right eye	oculus dexter	⚠ Read, don't write	Confused with AD (right ear). "o.d." meaning once daily is a separate ISMP warning.	2, 7
OS	left eye	oculus sinister	⚠ Read, don't write	Confused with AS (left ear).	2, 7
OU	each eye	oculus uterque	⚠ Read, don't write	Confused with AU (each ear).	2, 7
AD	right ear	auris dextra	⚠ Read, don't write	Confused with OD (right eye).	2, 7
AS	left ear	auris sinistra	⚠ Read, don't write	Confused with OS (left eye).	2, 7
AU	each ear	auris utraque	⚠ Read, don't write	Confused with OU (each eye).	2, 7
NPO	nothing by mouth	nil per os	Read		6, 8
AAA	apply to affected area		Read	Not the same as aa ("of each").	7

Dosage forms

21 entries

Dosage forms
Code	Meaning	Latin root	Flag	Note	Source
tab	tablet	tabella	Read		6, 7
cap	capsule	capsula	Read		6, 7
ODT	orally disintegrating tablet		Read		7
supp	suppository	suppositorium	Read		6, 7
susp	suspension		Read		6, 7
sol	solution	solutio	Read		6, 7
syr	syrup	syrupus	Read		6, 7
elix	elixir		Read		6
ung, oint	ointment	unguentum	Read		6, 7
cr, crm	cream		Read	"cr" can be confused with CR (controlled release).	6
lot	lotion	lotio	Read		6, 7
troch	lozenge	trochiscus	Read		6, 7
gtt, gtts	drop, drops	gutta	Read	Doesn't say eye or ear. The site code does.	6, 7
inj (also IJ)	injection	injectio	⚠ Read, don't write	The safety warning applies to IJ, which can be confused with IV or intrajugular. Write "injection" rather than IJ.	2, 6, 7
MDI	metered-dose inhaler		Read		8
amp	ampule	ampulla	Read		7, 8
EC	enteric-coated		Read		6, 7
ER, XR, XL	extended-release		Read		6, 7
DR	delayed-release		Read		6, 7
SR	sustained-release		Read		6
IR	immediate-release		Read		6, 7

Amounts, units, and numerals

21 entries

Amounts, units, and numerals
Code	Meaning	Latin root	Flag	Note	Source
mL	milliliter		Read	Capital L. ISMP warns that a lowercase l can look like the number 1.	2, 6
L	liter		Read	Capital L for the same reason.	2, 7
mg	milligram		Read		6, 7
mcg	microgram		Read	ISMP says write mcg, never µg. Still check it against mg: a 1,000-fold difference.	2, 5, 6
g	gram		Read		6, 7
kg	kilogram		Read		6, 7
gr	grain	granum	⚠ Read, don't write	Old apothecary unit, mistaken for gram. Use metric.	2, 6
tsp	teaspoon (5 mL)		⚠ Read, don't write	Know the conversion. ISMP says labels should use mL.	2, 6
tbsp, Tbsp	tablespoon (15 mL)		⚠ Read, don't write	Teaspoon and tablespoon get swapped. Use mL.	2, 6
oz	fluid ounce (29.57 mL, often rounded to 30 mL)		⚠ Read, don't write	Use metric.	2, 6
lb	pound	libra	Read	ISMP says don't use # for pounds.	2, 7
cc	cubic centimeter (1 cc = 1 mL)		⚠ Read, don't write	Misread as u (units). Write mL.	2, 6
U, u	unit		⛔ Do Not Use	Read as 0 or 4 (4U seen as 40) or as cc. Write "units."	2, 5, 6
IU	international unit		⛔ Do Not Use	Read as IV or the number 10. Write "units."	2, 5, 6
mEq	milliequivalent		Read		8
qs	a sufficient quantity	quantum sufficiat	Read		6, 7
qs ad	add enough to reach the stated total		Read		8
aa	of each	ana	Read	"aa 30 g" means 30 g of each ingredient.	7
i, ii, iii	one, two, three		Read	PTCB's outline names Roman numerals (4.1). ISMP says doses should be written in Arabic numerals.	1, 2, 8
iv, v, x	four, five, ten		Read	Standard Roman numeral values. See the numeral table below the list.	1, 7
ss	one-half	semis	⚠ Read, don't write	Can be misread as 55. ISMP says write "half tablet," not a fraction or decimal.	2, 3, 8

Prescription and dispensing

15 entries

Prescription and dispensing
Code	Meaning	Latin root	Flag	Note	Source
Rx	prescription; "take"	recipe	Read		6, 7
Sig	write/label the directions	signa	Read	The Sig is the directions-for-use part of a prescription; this page also includes related prescription and dispensing abbreviations.	7, 8
disp	dispense		Read		7
DAW	dispense as written (no substitution)		Read		6, 7
non rep.	do not repeat (no refills)	non repetatur	Read		8
m	mix	misce	Read	M can also stand for mitte (send). Read the context.	8
f, ft	make; let it be made	fiat	Read		7, 8
m ft	mix and make (m ft ung = mix and make an ointment)	misce, fiat	Read	Not "mix and shake."	8
dil	dilute		Read		7
div	divide		Read		7
ad lib	freely; as much as desired	ad libitum	Read		7
NKA, NKDA	no known allergies; no known drug allergies		Read		6
D/C	discontinue, or discharge		⚠ Read, don't write	Two meanings. Write the word you mean.	2, 7
N&V	nausea and vomiting		Read		6
SOB	shortness of breath		Read		7

Drug-name abbreviations to recognize

4 entries

Drug-name abbreviations to recognize
Code	Meaning	Flag	Note	Source
APAP	acetaminophen	⚠ Read, don't write	Not everyone recognizes it. Spell it out.	2, 6, 7
HCTZ	hydrochlorothiazide	⚠ Read, don't write	Mistaken for hydrocortisone, and HCT (meant as hydrocortisone) is mistaken for HCTZ.	2
MS, MSO4	morphine sulfate	⛔ Do Not Use	Confused with magnesium sulfate.	2, 6
MgSO4	magnesium sulfate	⛔ Do Not Use	Confused with morphine sulfate.	2, 6

Periods and capitals vary from prescriber to prescriber: b.i.d., bid, and BID mean the same thing. The one case-sensitive trap on this list is bedtime, covered in the Frequency and timing notes.

Quiz yourself: cover the Meaning column, say each meaning out loud, then check. Next round, cover the Code column and work backward.

How to read any sig in five moves

Read it left to right and pull out five pieces:

How much: the number and the unit or dosage form (ii tabs, 5 mL, i gtt).
Where: the route or site (po, SL, OU, AU).
How often: the frequency or interval, exactly as written (bid, q6h).
Anything extra: meals, bedtime, the prn reason, a duration, a max.
Say it back in plain English. If a piece is missing, conflicts with the product, or could mean two things, stop and ask the pharmacist. Don't guess.

That order is a study habit, not a rule prescribers follow. The directions below are made-up study examples, not real prescriptions or treatment advice.

Example 1. ii tabs po q6h prn pain x5d

How to read any sig in five moves
Piece	Code	Meaning
How much	ii tabs	2 tablets
Where	po	by mouth
How often	q6h	every 6 hours
Extra	prn pain	as needed for pain
Extra	x5d	for 5 days

Plain English: Take 2 tablets by mouth every 6 hours as needed for pain for 5 days.

Example 2. 1 tab PO BID pc for 14 days

Plain English: Take 1 tablet by mouth twice a day after meals for 14 days. Quantity: 1 tablet × 2 a day × 14 days = 28 tablets.

Example 3. Disp 84 tablets, 2 tabs PO BID

Plain English: Take 2 tablets by mouth twice a day. Daily use: 2 × 2 = 4 tablets. Days' supply: 84 ÷ 4 = 21 days, assuming every dose is taken as written.

BID isn't the same instruction as q12h

bid counts doses per day. q12h sets a 12-hour gap between doses. The same goes for tid versus q8h and qid versus q6h. When you translate, keep what the prescriber wrote. Don't swap one for the other, and don't add clock times that aren't in the sig.

Roman numerals on prescriptions

PTCB names Roman numerals in the same knowledge area as sig codes (PTCE Content Outline, 4.1). On prescriptions you'll usually see them in lowercase: i, ii, iii.

Roman numerals on prescriptions
Numeral	I	II	III	IV	V	VI	VII	VIII	IX	X
Value	1	2	3	4	5	6	7	8	9	10

A smaller numeral after a larger one adds: VI = 5 + 1 = 6.
A smaller numeral before a larger one subtracts: IV = 5 − 1 = 4, and IX = 10 − 1 = 9.
ss means one-half (semis), so "ii ss" would be two and a half.
Lowercase iv (4) uses the same letters as IV (intravenous). Context usually settles it. When it doesn't, ask.

You need to read Roman numerals, but ISMP recommends writing doses only in Arabic numerals (1, 2, 3) because Roman numerals get misread (ISMP list, p. 6).

Practice: 30 sig code questions

These are original practice questions written by Castleport, not official or recalled PTCB questions. Your result is feedback on these 30 items. It isn't a PTCE score or a prediction of passing. Each answer and explanation sits right under its question.