Error-Prone Symbols

Error-Prone Symbols


The symbols found in this table have been reported to
the Institute for Safe Medical Practices (ISMP) through the ISMP
Medication Error Reporting Program as being frequently misinterpreted and
involved in harmful medication errors. These symbols 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.

Symbol Intended 
Misinterpretation Correction
ʒ Dram Mistaken as “3” Use the metric system
Minim Mistaken as “mL” Use the metric system
x1 Administer once Administer for 1 day Use explicit words (eg, “for 1 dose”)
> and < More than and less than Mistaken as opposite of intended; incorrect symbol used mistakenly; “<” mistaken as “4” when handwritten (eg, “<10” mistaken as “40”) Use “more than” or “less than”
↑ and ↓ Increase and decrease Mistaken as opposite of intended; incorrect symbol used mistakenly; ↑ 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 (eg, “25 units/10units” mistaken as “25 units and 110 units”) Use “per” rather than a slash mark to separate doses
@ At Mistaken as “2” Use “at”
& And Mistaken as “2” Use “and”
+ Plus or and Mistaken as “4” Use “plus”, “and”, or “in addition to”
° Hour Mistaken as a zero (eg, q2° seen as q 20) Use “hr”, “h”, or “hour”
Φ or ∅ Zero, null sign Mistaken as numerals 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; if referring to pounds, use “lb”

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

Available at: error-prone-abbreviations-list. Accessed August 24, 2022.

(Rev. 9/2022)