Making sure that you correctly calculate a dose doesn’t matter much if the medication itself is incorrect or the dosing instructions are unclear. Some abbreviations in prescriptions are unacceptable because they cause ambiguity and confusion (the enemies of patient safety and quality healthcare!). For this reason, you don’t want to see these abbreviations on any medical orders you work with.

Abbreviation Mistaken Meanings Better Choice
DC or D/C Does it mean “discontinue” or “discharge”? Write discontinue or discharge.
HS Does it mean “half-strength” or “at bedtime”? Write at bedtime or a designated time.
Also write out the specific dosing strength and/or quantity
QD Does it mean “every day” or “right eye”? QD looks like OD, which means “right eye.” (OS means “left eye.”) Write every day.
QOD Does it mean “every other day” or “daily”? Write every other day or daily, according to patient’s needs.
MSO4 Does it mean “magnesium sulfate” or “morphine sulfate”? Write magnesium sulfate or morphine sulfate.
U or IU Does it mean “unit” or “zero”? Could it be mistaken for “0” or “10”? Write units.
IV Does it mean “intravenous,” “international units,” or “4”? IV is an acceptable abbreviation for “intravenous,” but the doc could write international units or intravenous to be clearer.
Or “4”
SQ or SC Does it mean “subcutaneous” or could it be mistaken for “5Q” (“5 every”)? Write Subq, subcut, subcutaneous, or 5 every.
TIW Does it mean “twice a week” or “three times a week” (the real meaning)? Write twice a week or three times a week.
cc Does it mean “cubic centimeter” or “milliliter”? Could it be mistaken for “00”? Write milliliter or mL.
Ug or g Does it mean “microgram” or “Ugh”? Could it be mistaken for mg? Write microgram or mcg.
OD Does it mean “once daily” or “right eye”? Write once daily or right eye.

Source: The National Coordinating Council for Medication Error Reporting and Prevention (NCC MERP).