The ISMP List of Error-Prone Abbreviations, Symbols, and Dose Designations contains abbreviations, symbols, and dose designations which have been reported through the ISMP National Medication Errors Reporting Program (ISMP MERP) and have been misinterpreted and involved in harmful or potentially harmful medication errors. These abbreviations, symbols, and dose designations should NEVER be used when communicating medical information verbally, electronically, and/or in handwritten applications. This includes internal communications; verbal, handwritten, or electronic prescriptions; handwritten and computer-generated medication labels; drug storage bin labels; medication administration records; and screens associated with pharmacy and prescriber computer order entry systems, automated dispensing cabinets, smart infusion pumps, and other medication-related technologies.
In the Table, error-prone abbreviations, symbols, and dose designations that are included on The Joint Commission’s “Do Not Use” list (Information Management standard IM.02.02.01) are identified with a double asterisk (**) and must be included on an organization’s “Do Not Use” list. Error-prone abbreviations, symbols, and dose designations that are relevant mostly in handwritten communications of medication information are highlighted with a dagger (†).
How to cite: Institute for Safe Medication Practices (ISMP). ISMP List of Error-Prone Abbreviations, Symbols, and Dose Designations. ISMP; 2021.
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Error-Prone Abbreviations, Symbols, and Dose Designations |
Intended Meaning |
Misinterpretation |
Best Practice |
---|---|---|---|
Abbreviations for Doses/Measurement Units |
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cc |
Cubic centimeters |
Mistaken as u (units) |
Use mL |
IU** |
International unit(s) |
Mistaken as IV (intravenous) or the number 10 |
Use unit(s) |
l ml |
Liter Milliliter |
Lowercase letter l mistaken as the number 1 |
Use L (UPPERCASE) for liter Use mL (lowercase m, UPPERCASE L) for milliliter |
MM or M M or K |
Million Thousand |
Mistaken as thousand Mistaken as million M has been used to abbreviate both million and thousand (M is the Roman numeral for thousand) |
Use million Use thousand |
Ng or ng |
Nanogram |
Mistaken as mg Mistaken as nasogastric |
Use nanogram or nanog |
U or u** |
Unit(s) |
Mistaken as zero or the number 4, causing a 10-fold overdose or greater (e.g., 4U seen as 40 or 4u seen as 44) Mistaken as cc, leading to administering volume instead of units (e.g., 4u seen as 4cc) |
Use unit(s) |
µg |
Microgram |
Mistaken as mg |
Use mcg |
Abbreviations for Route of Administration |
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AD, AS, AU |
Right ear, left ear, each ear |
Mistaken as OD, OS, OU (right eye, left eye, each eye) |
Use right ear, left ear, or each ear |
IN |
Intranasal |
Mistaken as IM or IV |
Use NAS (all UPPERCASE letters) or intranasal |
IT |
Intrathecal |
Mistaken as intratracheal, intratumor, intratympanic, or inhalation therapy |
Use intrathecal |
OD, OS, OU |
Right eye, left eye, each eye |
Mistaken as AD, AS, AU (right ear, left ear, each ear) |
Use right eye, left eye, or each eye |
Per os |
By mouth, orally |
The os was mistaken as left eye (OS, oculus sinister) |
Use PO, by mouth, or orally |
SC, SQ, sq, or sub q |
Subcutaneous(ly) |
SC and sc mistaken as SL or sl (sublingual) SQ mistaken as “5 every” |
Use SUBQ (all UPPERCASE letters, without spaces or periods between letters) or subcutaneous(ly) |
Abbreviations for Frequency/Instructions for Use |
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HS hs |
Half-strength At bedtime, hours of sleep |
Mistaken as bedtime Mistaken as half-strength |
Use half-strength Use HS (all UPPERCASE letters) for bedtime |
o.d. or OD |
Once daily |
Mistaken as right eye (OD, oculus dexter), leading to oral liquid medications administered in the eye |
Use daily |
Q.D., QD, q.d., or qd** |
Every day |
Mistaken as q.i.d., especially if the period after the q or the tail of a handwritten q is misunderstood as the letter i |
Use daily |
Qhs |
Nightly at bedtime |
Mistaken as qhr (every hour) |
Use nightly or HS for bedtime |
Qn |
Nightly or at bedtime |
Mistaken as qh (every hour) |
Use nightly or HS for bedtime |
Q.O.D., QOD, q.o.d., or qod** |
Every other day |
Mistaken as qd (daily) or qid (four times daily), especially if the “o” is poorly written |
Use every other day |
q1d |
Daily |
Mistaken as qid (four times daily) |
Use daily |
q6PM, etc. |
Every evening at 6 PM |
Mistaken as every 6 hours |
Use daily at 6 PM or 6 PM daily |
SSRI SSI |
Sliding scale regular insulin
|
Mistaken as selective-serotonin reuptake inhibitor Mistaken as Strong Solution of Iodine (Lugol’s) |
Use sliding scale (insulin) |
TIW or tiw BIW or biw |
3 times a week 2 times a week |
Mistaken as 3 times a day or twice in a week Mistaken as 2 times a day |
Use 3 times weekly
|
UD |
As directed (ut dictum) |
Mistaken as unit dose (e.g., an order for “dilTIAZem infusion UD” was mistakenly administered as a unit [bolus] dose) |
Use as directed |
Miscellaneous Abbreviations Associated with Medication Use |
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BBA BGB |
Baby boy A (twin)
|
B in BBA mistaken as twin B rather than gender (boy) B at end of BGB mistaken as gender (boy) not twin B |
When assigning identifiers to newborns, use the mother’s last name, the baby’s gender (boy or girl), and a distinguishing identifier for all multiples (e.g., Smith girl A, Smith girl B) |
D/C |
Discharge or discontinue |
Premature discontinuation of medications when D/C (intended to mean discharge) on a medication list was misinterpreted as discontinued |
Use discharge and discontinue or stop |
IJ |
Injection |
Mistaken as IV or intrajugular |
Use injection |
OJ |
Orange juice |
Mistaken as OD or OS (right or left eye); drugs meant to be diluted in orange juice may be given in the eye |
Use orange juice |
Period following abbreviations (e.g., mg., mL.)† |
mg or mL |
Unnecessary period mistaken as the number 1, especially if written poorly |
Use mg, mL, etc., without a terminal period |
Drug Name Abbreviations |
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To prevent confusion, avoid abbreviating drug names entirely. Exceptions may be made for multi-ingredient drug formulations, including vitamins, when there are electronic drug name field space constraints; however, drug name abbreviations should NEVER be used for any medications on the ISMP List of High-Alert Medications (in Acute Care Settings, Community/Ambulatory Settings, and Long-Term Care Settings). Examples of drug name abbreviations involved in serious medication errors include: |
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Antiretroviral medications (e.g., DOR, TAF, TDF) |
DOR: doravirine TAF: tenofovir alafenamide TDF: tenofovir disoproxil fumarate |
DOR: Dovato (dolutegravir and lamiVUDine) TAF: tenofovir disoproxil fumarate TDF: tenofovir alafenamide |
Use complete drug names |
APAP |
acetaminophen |
Not recognized as acetaminophen |
Use complete drug name |
ARA A |
vidarabine |
Mistaken as cytarabine (“ARA C”) |
Use complete drug name |
AT II and AT III |
AT II: angiotensin II AT III: antithrombin III (Thrombate III) |
AT II (angiotensin II) mistaken as AT III (antithrombin III) AT III (antithrombin III) mistaken as AT II (angiotensin II) |
Use complete drug names |
AZT |
zidovudine (Retrovir) |
Mistaken as azithromycin, azaTHIOprine, or aztreonam |
Use complete drug name |
CPZ |
Compazine (prochlorperazine) |
Mistaken as chlorproMAZINE |
Use complete drug name |
DTO |
diluted tincture of opium or deodorized tincture of opium (Paregoric) |
Mistaken as tincture of opium |
Use complete drug name |
HCT |
hydrocortisone |
Mistaken as hydroCHLOROthiazide |
Use complete drug name |
HCTZ |
hydroCHLOROthiazide |
Mistaken as hydrocortisone (e.g., seen as HCT250 mg) |
Use complete drug name |
MgSO4** |
magnesium sulfate |
Mistaken as morphine sulfate |
Use complete drug name |
MS, MSO4** |
morphine sulfate |
Mistaken as magnesium sulfate |
Use complete drug name |
MTX |
methotrexate |
Mistaken as mitoXANTRONE |
Use complete drug name |
Na at the beginning of a drug name |
Sodium bicarbonate |
Mistaken as no bicarbonate |
Use complete drug name |
NoAC |
novel/new oral anticoagulant |
Mistaken as no anticoagulant |
Use complete drug name |
OXY |
oxytocin |
Mistaken as oxyCODONE, OxyCONTIN |
Use complete drug name |
PCA |
procainamide |
Mistaken as patient-controlled analgesia |
Use complete drug name |
PIT |
Pitocin (oxytocin) |
Mistaken as Pitressin, a discontinued brand of vasopressin still referred to as PIT |
Use complete drug name |
PNV |
prenatal vitamins |
Mistaken as penicillin VK |
Use complete drug name |
PTU |
propylthiouracil |
Mistaken as Purinethol (mercaptopurine) |
Use complete drug name |
T3 |
Tylenol with codeine No. 3 |
Mistaken as liothyronine, which is sometimes referred to as T3 |
Use complete drug name |
TAC or tac |
triamcinolone or tacrolimus |
Mistaken as tetracaine, Adrenalin, and cocaine; or as Taxotere, Adriamycin, and cyclophosphamide |
Use complete drug names Avoid drug regimen or protocol acronyms that may have a dual meaning or may be confused with other common acronyms, even if defined in an order set |
TNK |
TNKase |
Mistaken as TPA |
Use complete drug name |
TPA or tPA |
tissue plasminogen activator, Activase (alteplase) |
Mistaken as TNK (TNKase, tenecteplase), TXA (tranexamic acid), or less often as another tissue plasminogen activator, Retavase (retaplase) |
Use complete drug name |
TXA |
tranexamic acid |
Mistaken as TPA (tissue plasminogen activator) |
Use complete drug name |
ZnSO4 |
zinc sulfate |
Mistaken as morphine sulfate |
Use complete drug name |
Stemmed/Coined Drug Names |
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Nitro drip |
nitroglycerin infusion |
Mistaken as nitroprusside infusion |
Use complete drug name |
IV vanc |
Intravenous vancomycin |
Mistaken as Invanz |
Use complete drug name |
Levo |
levofloxacin |
Mistaken as Levophed (norepinephrine) |
Use complete drug name |
Neo |
Neo-Synephrine, a well known but discontinued brand of phenylephrine |
Mistaken as neostigmine |
Use complete drug name |
Coined names for compounded products (e.g., magic mouthwash, banana bag, GI cocktail, half and half, pink lady) |
Specific ingredients compounded together |
Mistaken ingredients |
Use complete drug/product names for all ingredients Coined names for compounded products should only be used if the contents are standardized and readily available for reference to prescribers, pharmacists, and nurses |
Number embedded in drug name (not part of the official name) (e.g., 5-fluorouracil, 6-mercaptopurine) |
fluorouracil mercaptopurine |
Embedded number mistaken as the dose or number of tablets/capsules to be administered |
Use complete drug names, without an embedded number if the number is not part of the official drug name |
Dose Designations and Other Information |
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1/2 tablet |
Half tablet |
1 or 2 tablets |
Use text (half tablet) or reduced font-size fractions (½ tablet) |
Doses expressed as Roman numerals (e.g., V) |
5 |
Mistaken as the designated letter (e.g., the letter V) or the wrong numeral (e.g., 10 instead of 5) |
Use only Arabic numerals (e.g., 1, 2, 3) to express doses |
Lack of a leading zero before a decimal point (e.g., .5 mg)** |
0.5 mg |
Mistaken as 5 mg if the decimal point is not seen |
Use a leading zero before a decimal point when the dose is less than one measurement unit |
Trailing zero after a decimal point (e.g., 1.0 mg)** |
1 mg |
Mistaken as 10 mg if the decimal point is not seen |
Do not use trailing zeros for doses expressed in whole numbers |
Ratio expression of a strength of a single-entity injectable drug product (e.g., EPINEPHrine 1:1,000; 1:10,000; 1:100,000) |
1:1,000: contains 1 mg/mL 1:10,000: contains 0.1 mg/mL 1:100,000: contains 0.01 mg/mL |
Mistaken as the wrong strength |
Express the strength in terms of quantity per total volume (e.g., EPINEPHrine 1 mg per 10 mL) Exception: combination local anesthetics (e.g., lidocaine 1% and EPINEPHrine 1:100,000) |
Drug name and dose run together (problematic for drug names that end in the letter l [e.g., propranolol20 mg; TEGretol300 mg]) |
propranolol 20 mg
|
Mistaken as propranolol 120 mg Mistaken as TEGretol 1300 mg |
Place adequate space between the drug name, dose, and unit of measure |
Numerical dose and unit of measure run together (e.g., 10mg, 10Units) |
10 mg 10 mL |
The m in mg, or U in Units, has been mistaken as one or two zeros when flush against the dose (e.g., 10mg, 10Units), risking a 10- to 100-fold overdose |
Place adequate space between the dose and unit of measure |
Large doses without properly placed commas (e.g., 100000 units; 1000000 units) |
100,000 units
|
100000 has been mistaken as 10,000 or 1,000,000 1000000 has been mistaken as 100,000 |
Use commas for dosing units at or above 1,000 or use words such as 100 thousand or 1 million to improve readability Note: Use commas to separate digits only in the US; commas are used in place of decimal points in some other countries |
Symbols |
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ʓ or ♏︎† |
Dram
|
Symbol for dram mistaken as the number 3 Symbol for minim mistaken as mL |
Use the metric system |
x1 |
Administer once |
Administer for 1 day |
Use explicit words (e.g., for 1 dose) |
> and < |
More than and less than |
Mistaken as opposite of intended Mistakenly have used the incorrect symbol < mistaken as the number 4 when handwritten (e.g., <10 misread as 40) |
Use more than or less than |
↑ and ↓† |
Increase and decrease |
Mistaken as opposite of intended Mistakenly have used the incorrect symbol ↑ mistaken as the letter T, leading to misinterpretation as the start of a drug name, or mistaken as the numbers 4 or 7 |
Use increase and decrease |
/ (slash mark)† |
Separates two doses or indicates per |
Mistaken as the number 1 (e.g., 25 units/10 units misread as 25 units and 110 units) |
Use per rather than a slash mark to separate doses |
@† |
At |
Mistaken as the number 2 |
Use at |
&† |
And |
Mistaken as the number 2 |
Use and |
+† |
Plus or and |
Mistaken as the number 4 |
Use plus, and, or in addition to |
° |
Hour |
Mistaken as a zero (e.g., q2° seen as q20) |
Use hr, h, or hour |
Ф or ᴓ† |
Zero, null sign |
Mistaken as the numbers 4, 6, 8, and 9 |
Use 0 or zero, or describe intent using whole words |
# |
Pound(s) |
Mistaken as a number sign |
Use the metric system (kg or g) rather than pounds Use lb if referring to pounds |
Apothecary or Household Abbreviations |
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Explicit apothecary or household measurements may ONLY be safely used to express the directions for mixing dry ingredients to prepare topical products (e.g., dissolve 2 capfuls of granules per gallon of warm water to prepare a magnesium sulfate soaking aid). Otherwise, metric system measurements should be used. |
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gr |
Grain(s) |
Mistaken as gram |
Use the metric system (e.g., mcg, g) |
dr |
Dram(s) |
Mistaken as doctor |
Use the metric system (e.g., mL) |
min |
Minim(s) |
Mistaken as minutes |
Use the metric system (e.g., mL) |
oz |
Ounce(s) |
Mistaken as zero or 02 |
Use the metric system (e.g., mL) |
tsp |
Teaspoon(s) |
Mistaken as tablespoon(s) |
Use the metric system (e.g., mL) |
tbsp or Tbsp |
Tablespoon(s) |
Mistaken as teaspoon(s) |
Use the metric system (e.g., mL) |
Common Abbreviations with Contradictory |
Contradictory Meanings |
Correction |
|
For additional information and tables from Neil Davis (MedAbbrev.com) containing additional examples of abbreviations with contradictory or ambiguous meanings, please click here. |
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B |
Breast, brain, or bladder |
Use breast, brain, or bladder |
|
C |
Cerebral, coronary, or carotid |
Use cerebral, coronary, or carotid |
|
D or d |
Day or dose |
Use day or dose |
|
H |
Hand or hip |
Use hand or hip |
|
I |
Impaired or improvement |
Use impaired or improvement |
|
L |
Liver or lung |
Use liver or lung |
|
N |
No or normal |
Use no or normal |
|
P |
Pancreas, prostate, preeclampsia, or psychosis |
Use pancreas, prostate, preeclampsia, or psychosis |
|
S |
Special or standard |
Use special or standard |
|
SS or ss |
Single strength, sliding scale (insulin), signs and symptoms, or ½ (apothecary) SS has also been mistaken as the number 55 |
Use single strength, sliding scale, signs and symptoms, or one-half or ½ |
** On The Joint Commission’s “Do Not Use” list
† Relevant mostly in handwritten medication information
While the abbreviations, symbols, and dose designations in the Table should NEVER be used, not allowing the use of ANY abbreviations is exceedingly unlikely. Therefore, the person who uses an organization-approved abbreviation must take responsibility for making sure that it is properly interpreted. If an uncommon or ambiguous abbreviation is used, and it should be defined by the writer or sender. Where uncertainty exists, clarification with the person who used the abbreviation is required.