Error-Prone Dose Designations

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, telephone/verbal prescriptions, computer-generated labels, labels for drug storage bins, medication administration records, as well as pharmacy and prescriber computer order entry screens.

Dose Designations
and Other Information
Misinterpretation Correction
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
“Naked” 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
Abbreviations such as mg. or mL. with a period following the abbreviation mg
The period is unnecessary and could be mistaken as the number 1 if written poorly Use mg, mL, etc. without a terminal period
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, 100mL)
10 mg
100 mL
The “m” is sometimes mistaken as a zero or two zeros, 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. Error-Prone Abbreviations, Symbols, and Dose Designations. 2015.

Available at:

(Rev. 5/2018)