Error-Prone Dose Designations


The dose designations found in this table have been reported to the Institute for Safe Medication Practices (ISMP) through the ISMP National Medication Errors Reporting Program (ISMP MERP) as being frequently misinterpreted and involved in harmful medication errors. They should never be used when communicating medical information. 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.

Dose Designations
and Other Information
Misinterpretation Correction
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 (eg, V) 5 Mistaken as the designated letter (eg, the letter V) or the wrong numeral (eg, 10 instead of 5) Use only Arabic numerals (eg, 1, 2, 3) to express doses
Trailing zero after decimal point* (eg, 1.0mg) 1mg Mistaken as 10mg if the decimal point is not seen Do not use trailing zeros for doses expressed in whole numbers
Lack of leading zero before decimal point* (eg, .5mg) 0.5mg Mistaken as 5mg if the decimal point is not seen Use zero before a decimal point when the dose is less than a whole unit
Ratio expression of a strength of a single-entity injectable drug product (eg, 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 (eg, EPINEPHrine 1 mg per 10 mL)
Exception: combination local anesthetics (eg, lidocaine 1% and EPINEPHrine 1:100,000)
Drug name and dose run together (especially problematic for drug names that end in “I” such as Inderal40 mg; TEGretol300mg) Inderal 40mg Mistaken as Inderal 140mg Place adequate space between the drug name, dose, and unit of measure
TEGretol 300mg Mistaken as TEGretol 1300mg
Numerical dose and unit of measure run together
(eg, 10mg, 10Units)
10 mg
10 Units
The “m” or “U” has been mistaken as one or two zeros when flush against the dose, risking a 10- to 100-fold overdose Place adequate space between the dose and unit of measure
Large doses without properly placed commas
(eg, 100000 units; 1000000 units)
100,000 units
1,000,000 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

*These abbreviations are included on The Joint Commission’s “minimum list” of dangerous abbreviations, acronyms, and symbols that must be included on an organization’s “Do Not Use” list, effective January 1, 2004. Visit for more information about this Joint Commission requirement.


Source: Institute for Safe Medication Practices. List of Error-Prone Abbreviations. 2021.

Available at: Accessed November 12, 2021.

(Rev. 11/2021)