Abbreviation Intended meaning Common Error
U Units Mistaken as a zero or a four (4) resulting in
overdose. Also mistaken for "cc"
(cubic centimeters) when poorly written.
µg Micrograms Mistaken for "mg" (milligrams) resulting in
Q.D. Latin abbreviation for The period after the "Q" has sometimes been
every day mistaken for an " I, " and the drug
has been given "QID" (four times daily) rather
Q.O.D. Latin abbreviation for Misinterpreted as "QD" (daily) or "QID" (four
every other day times daily). If the "O" is
poorly written, it looks like a period or "I."
SC or SQ Subcutaneous Mistaken as "SL" (sublingual) when poorly
T I W Three times a week Misinterpreted as "three times a day" or
"twice a week."
D/C Discharge; also discontinue Patient's medications have been prematurely
discontinued when D/C, (intended to mean
"discharge") was misinterpreted
as "discontinue," because it was followed
by a list of drugs.
HS Half strength Misinterpreted as the Latin abbreviation "HS"
(hour of sleep).
cc Cubic centimeters Mistaken as "U" (units) when poorly written.
AU, AS, AD Latin abbreviation for both ears; Misinterpreted as the Latin abbreviation "OU"
left ear; right ear (both eyes); "OS" (left eye); "OD" (right eye)
IU International Unit Mistaken as IV (intravenous) or 10(ten)
MS, MSO4, Confused for one another Can mean morphine sulfate or magnesium
See the full Council Recommendation, Recommendations to Enhance Accuracy of Prescription Writing.