Prescription Abbreviations: What Do They Mean?

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on Nov 28, 2023.

What are Pharmacy Abbreviations? | Safety | Common Errors | Preventing Errors | Table of Common Prescription Abbreviations

You may wonder what medical abbreviations like "1 tab po bid" mean on your prescription. Healthcare professionals often use abbreviations derived from latin for writing prescriptions or other health notes in medical records.

The prescription abbreviation "1 tab po bid" is interpreted like this:

• the abbreviation "tab" means tablet and comes from the latin tabella
• "po" means by mouth and comes from per os
• "bid" means twice a day, and derives from bis in die.

When written out in plain language, these abbreviations mean "Take one tablet by mouth twice a day."

Luckily you don’t have to worry about interpreting these prescription directions yourself. It’s the pharmacist’s job to put the correct directions on your prescription label. But unclear or poorly written prescription abbreviations is one of the most common and preventable causes of medication errors.

• To address these issues, healthcare agencies such as the Food and Drug Administration (FDA) and the Institute for Safe Medication Practices (ISMP) have made it a priority to communicate information about confusing abbreviations and medical shorthands.
• Health care facilities, practitioners and medical record systems have standards to help prevent these common and potentially dangerous medical errors.

Are medical abbreviations safe to use?

Historically, poor penmanship and lack of standardization was the root cause of many written paper prescription errors. Today, most prescriptions are submitted via electronic prescribing (e-prescribing), electronic medical records (EMRs), and computerized physician order entry (CPOE), which has helped to lower the rates of these medical errors.

Even with advances in technology, errors or misunderstanding in electronic prescriptions can occur. Computer-generated abbreviations, prescription symbols, and dose designations can still be confusing and lead to mistakes in drug dosing or timing. In addition, when these abbreviations are unclear, extra time must be spent by pharmacists or other healthcare providers trying to clarify their meanings, which can delay medical treatments.

If you receive a prescription label with unclear and confusing directions, always call your doctor or pharmacist right away to double check the information. 

Common Abbreviation errors

1. Drug names

Drug names may be frequently abbreviated in medicine. For example, cancer treatment protocols or combination HIV regimens may be written with shortened drug name abbreviations. Examples of possible errors include:

• Acetaminophen (Tylenol), a common over-the-counter pain medicine, is often shortened to "APAP" by healthcare providers, although ISMP states it should be spelled out instead, as not everyone recognizes this abbreviation.
• As reported by the FDA, a prescription with the abbreviation “MTX” has been interpreted as both methotrexate (used for rheumatoid arthritis) or mitoxantrone (a cancer drug). “ATX” can be misunderstood to be the shorthand for zidovudine (AZT, an HIV drug) or azathioprine (an immunosuppressant drug).
• "IU", which is intended to mean international units can be misinterpreted to mean IV (intravenous) or the number 10.
• These types of errors may lead to significant patient harm.

2. Confusing numbers

Numbers can lead to confusion and drug dosing errors, too.

• As an example, a prescription for “furosemide 40 mg Q.D.” (40 mg daily) was misinterpreted as “QID” (40 mg four times a day), leading to a serious medical error.
• Another example has to do with drug dosage units: doses in micrograms should always have the unit spelled out, because the abbreviation “µg” (micrograms) can easily be misread as “mg” (milligrams), creating a 1000-fold overdose.

3. Trailing zeros on medication orders

Numbers can also be misinterpreted with regards to decimal points. As noted in the Joint Commission's Do Not Use List, a trailing zero (for example, "5.0" mg, where the zero follows a decimal point) can be misinterpreted as “50” mg leading to a 10-fold overdose. Instead the prescriber should write “5 mg” with no trailing zero or decimal point after the number. Also, the lack of a leading zero, (for example, .9 mg) can be misread as “9” mg; instead the prescriber should use “0.9 mg” to clarify the strength.

The Joint Commission notes an exception to the Trailing Zero warning. They state that a “trailing zero may be used only when required to demonstrate the level of precision of the value being reported, such as for laboratory results, imaging studies that report the size of lesions, or catheter/tube sizes. It may not be used in medication orders or other medication-related documentation."

4. Modified-release dose forms

Common abbreviations are often used for modified-release types of technology for prescription drugs, although no true standard exists for this terminology.

• Many drugs exist in special formulation as tablets or capsules -- for example as ER, XR, and SR -- to slow absorption or alter where the dissolution and absorption occurs in the gastrointestinal tract.
• Timed-release technology allows drugs to be dissolved over time, allows more steady blood concentrations of drugs, and can lower the number of times a drug must be taken per day compared to immediate-release (IR) formulations.
• Enteric-coated formulations, such as enteric-coated aspirin, help to protect the stomach by allowing the active ingredient to bypass dissolution in the stomach and instead dissolve in the intestinal tract.

How to prevent medication errors

Healthcare providers can:

• Completely write out (or select electronically) the prescription, including the drug name and dosage regimen. The full dosage regimen includes the dose, frequency, duration, and route of administration of the drug to be administered.
• When writing out a dose, DO NOT use a trailing zero and DO use a leading zero.
• For veterinarians, when calling in or writing out a human drug prescription for an animal, verbally state or write out the entire prescription because some pharmacists may be unfamiliar with veterinary abbreviations.
• Use a computerized prescription system and electronic delivery of prescriptions to help lower the risk of confusion due to poor handwriting.
• Medical facilities should regularly educate and update healthcare providers and other employees on proper use of abbreviations.
• Report adverse events that stem from medication errors or abbreviations errors to the FDA; these events can be used to further inform and expand recommendations for safety.

In general, to avoid errors in the administration of medications and infusions, spell out the word instead of using an abbreviation. For example, use “international unit” instead of I.U.; “every day” instead of q.d.; “every other day” instead of q.o.d.; and “unit” instead of U.

Practitioners, including physicians, nurses, pharmacists, physician assistants and nurse practitioners, should be very familiar with the abbreviations used in medical practice and in prescription writing. All drug names, dosage units, and directions for use should be written clearly to avoid misinterpretation.

Pharmacists should be included in teams that develop or evaluate EMRs and e-prescribing tools. According to the Joint Commission, health care organizations can develop their own internal standards for medical abbreviations, use a published reference source with consistent terms, and should ensure that multiple abbreviations for the same word are avoided. Internal enforcement, regular review and consistency are always the key.

Joint Commission provides a list of mandatory "Do Not Use" abbreviations that must be applied to all orders, preprinted forms, and medication-related documentation (see notes in table below). Medication-related documentation can be either handwritten or electronic. Organizations are required by Joint Commission to follow this list of prohibited abbreviations, acronyms, symbols, and dose designations. However, the Joint Commission does not publish a list of approved abbreviations.  

What can you do as a patient?

• Ask your doctor how you are supposed to take your medication before you leave the office, and write it down for future reference. 
• Consider taking a trusted family member or friend to your medical appointments to help you to record important instructions.
• Read the supplied plain language patient drug information that accompanies your prescription. If you do not have it, ask your doctor or pharmacist for a copy. Your healthcare professional can answer any questions about this information.
• If you receive a prescription with unusual, unexpected or confusing directions, be sure to double check with your doctor and pharmacist.
• FDA encourages all healthcare providers, patients and consumers to report medication errors to the FDA Medwatch Program. This program alerts the FDA to potential problems and allows them to take action to minimize further errors. Timely prevention of medical errors can save a patient’s life.

Table of Common Medical / Prescription Abbreviations

Note: This is not a complete or endorsed list of medical or prescription abbreviations or error-prone abbreviations. The Joint Commission does not publish a list of approved abbreviations. Always speak with your healthcare provider for any questions related to medical abbreviations or terms. Items below marked with ** are found on the Joint Commission's "Do Not Use" List of Abbreviations.

Common Abbreviation	Meaning or Intended Meaning	Best practice / Notes on any confusion
1/2 tablet	one-half tablet	Spell out half tablet or use reduced font-size fractions (½ tablet)
5-ASA	5-aminosalicylic acid	Better to spell out full drug name 5-aminosalicylic acid; may be misinterpreted as 5 aspirin tablets.
ā	before
ac	before meals
achs	before meals and at bedtime
AD	right ear	Spell out right ear; may be mistaken for OD (right eye)
AS	left ear	Spell out left ear; may be mistaken for OS (left eye)
AU	each ear	Spell out each ear; may be mistaken for OD (each eye)
A.M.	morning
APAP	acetaminophen	Spell out acetaminophen; not everyone familiar with abbreviation.
ASA	aspirin	Better to spell out full drug name aspirin.
AZT	zidovudine	Better to spell out full drug name zidovudine; can be mistaken as azithromycin, azathioprine, or aztreonam.
bid	twice a day
BMI	body mass index
BP	blood pressure
BSA	body surface area
c̅	with
C&S	culture and sensitivity
CaCO3	calcium carbonate
CAD	coronary artery disease
cap	capsule	Spell out capsule; may be confused with cancer of the prostate (CAP).
CBC	complete blood count
cc	cubic centimeter	Use mL; can be mistaken as "u" (units).
C&S	culture and sensitivity
cm	centimeters
CNS	central nervous system
CPZ	Compazine (generic: prochlorperazine)	Better to spell drug name Compazine out; can be misinterpreted as chlorpromazine.
CR	controlled release
cr, crm	cream
CV	cardiovascular
CXR	chest xray
D/C, dc, or disc	discontinue or discharge	Multiple meanings; spell out discontinue or discharge.
DAW	dispense as written
disp	dispense
DM	diabetes mellitus
DO	Doctor of Osteopathy
DOB	date of birth
DR	delayed release
DVT	deep vein thrombosis
EC	enteric coated
EENT	eye, ear, nose, throat
elix	elixir
ER	emergency room or extended release	Best to spell out intended meaning
F	fahrenheit
FBS	fasting blood sugar
FDA	Food and Drug Administration
Fe	iron
G, g, gm	gram	Use g as preferred symbol
gr.	grain	Can be mistaken as gram; use metric system.
garg	gargle
GERD	gastroesophageal reflux disease
GI	gastrointestinal
GU	genitourinary
gtt, gtts	drop, drops	Use drop or drops; Can be confused with GTT for glucose tolerance test.
h, hr	hour
h/o	history of
H2O	water
HCP	health care professional
HCT	hydrocortisone	Spell out hydrocortisone; can be mistaken as hydrochlorothiazide.
HCTZ	hydrochlorothiazide	Spell out hydrochlorothiazide; can be mistaken as hydrocortisone.
HDL	high density lipoprotein
HS	half-strength	Spell out half strength; HS may be mistaken as bedtime.
hs	bedtime	Use upper case HS for bedtime; hs may be mistaken for half-strength.
HTN	hypertension
hx	history
IBW	ideal body weight
IM	intramuscular
IN	intranasal	Spell out intranasal or use NAS (all uppercase letters); can be confused with IV or IM.
IJ	injection	Spell out injection; can be confused with intrajugular or IV.
IR	immediate-release
IU**	international unit	Mistaken as IV (intravenous) or "ten"; instead spell out "units" per Joint Commission's "Do Not Use" List of Abbreviations.
IUD	intrauterine device
IV	intravenous
IVP	intravenous push
K	potassium
KOH	potassium hydroxide
L	liter	Use upper case L
LA	long-acting
lab	laboratory
Lack of leading zero (.X mg)**	0.X mg	Decimal point is missed; Write 0.X mg; per Joint Commission's "Do Not Use" List of Abbreviations.
lb	pound
LDL	low density lipoprotein
LFT	liver function tests
liq	liquid
lot	lotion
LPN	licensed practical nurse
mcg, µg	microgram	Can be misinterpreted to mean mg or milligram, better to spell out microgram.
MD	medical doctor, muscular dystrophy
MDI	metered dose inhaler
Mg	magnesium
mg	milligram
MgSO4**	magnesium sulfate	Spell out magnesium sulfate per Joint Commission's "Do Not Use" List of Abbreviations. Can be confused with MSO4 (morphine sulfate).
mL	milliliter	Use mL; use lower case m and upper case L for milliliter.
mm	millimeter
MS, MSO4**	morphine sulfate	Spell out morphine sulfate per Joint Commission's "Do Not Use" List of Abbreviations. Can be confused with magnesium sulfate (MgSO4). MS can also stand for multiple sclerosis.
N&V	nausea and vomiting
Na	sodium
NAS	intranasal	Use NAS (all upper case letters) or spell out intranasal.
NDC	National Drug Code
NGT	nasogastric tube
NH3	ammonia
NKA	No known allergies
NKDA	No known drug allergies
NPO	Nothing by mouth	Spell out nothing by mouth - preferred by American Medical Association (AMA).
NS	normal saline
NSAID	nonsteroidal anti-inflammatory drug
OC	oral contraceptive
OD	right eye	Spell out right eye; may be confused for overdose or once daily
OJ	orange juice
OM	otitis media
OS	left eye	Spell out left eye; may be mistaken for AS (right ear)
OTC	over-the-counter
OU	both eyes
oz	ounce
p (with line on top)	after
prn	as needed
PA	physician assistant
pc	after meals
PCA	patient-controlled analgesia
PE	pulmonary embolism or physical exam
per neb	by nebulizer
per os	by mouth	May be preferred to spell out by mouth or orally; can be mistaken as os (left eye) per FDA
PFT	pulmonary function tests
PharmD	Doctor of Pharmacy
PM	evening
PMH	past medical history
PO, p.o.	by mouth or orally	May be preferred to spell out by mouth or orally
PR	per rectum
PRN	as needed
PT	prothrombin time
PV	per vagina
q	every
qs	as much as needed; a sufficient quantity
q12h	every 12 hours
qd	every day
q6h	every 6 hours
q8h	every 8 hours
qam	every morning
qd, QD**	every day	Mistaken as q.i.d; Instead write daily per Joint Commission's "Do Not Use" List of Abbreviations.
qh	every hour
qhs	each night at bedtime	Can be confused with qh (every hour); better to spell out each night at bedtime.
qid, QID	four times a day
qod, q.o.d, QOD, Q.O.D**	every other day	Can be mistaken as qd (daily) or qid (four times daily); Period after the Q mistaken for "I" and the "O" mistaken for "I". Instead spell out "every other day" per Joint Commission's "Do Not Use" List of Abbreviations.
RA	rheumatoid arthritis
RN	registered nurse
RPh	Pharmacist
Rx	prescription
s (with line over s)	without
SA	sustained action
SL, s.l.	sublingual (under the tongue)
SNRI	serotonin norepinephrine reuptake inhibitor
sol	solution, in solution
SQ, SC, sub q	subcutaneous	Use caution as SC can be mistaken for SL (sublingual) per FDA.
SR	sustained release
SSI	sliding scale insulin	Write out sliding scale insulin
SSRI	selective serotonin reuptake inhibitor	Spell out to avoid confusion
stat	immediately
supp	suppository
susp.	suspension
syr.	syrup
T	temperature
tab	tablet
tbsp	tablespoon
TID, t.i.d.	three times a day
tid ac	three times a day before meals
tinct., tr	tincture
top	topical
TR	timed-release
Trailing zero (X.0 mg)**	X mg	Decimal point may be missed; Write X mg; per Joint Commission's "Do Not Use" List of Abbreviations. See exception to Trailing Zero above.
TSH	thyroid stimulating hormone
troche	lozenge
tsp	teaspoon
Tx	treatment
U or u**	unit	Mistaken as the number "0" (zero), the number "4" (four), or "cc". Prescriber should instead spell out "unit" per Joint Commission's "Do Not Use" List of Abbreviations
UA	urinalysis
ud, ut dict, UD	as directed
ung	ointment
UTI	urinary tract infection
vol	volume
WBC	white blood cell
WNL	within normal limits
XL, XR, XT	extended-release
yo	years old
yr	year
Zn	zinc
μg, mcg	microgram	spell out microgram

See also

• Are expired drugs still safe to take?
• Common Drug Side Effects
• Does grapefruit juice interact with my medications?
• Generic Drug FAQs
• How do I remember to take my medications?
• How do I stop my medication safely?
• How to Safely Dispose of Your Old Medications
• Imprint Code FAQs - For Oral Medications
• Injection Types and Sites
• Medical Conversions - How many mL in a teaspoon?
• Pill splitting - Is it safe?
• Top 5 Ways to Avoid Drug Errors
• Top 9 Ways to Prevent a Deadly Drug Interaction
• What are pharmaceutical salt names?
• What are the risks vs. benefits of medications?
• What is the half-life of a drug?
• What is the placebo effect?

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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