Overview of Abbreviations on Prescriptions

Interpreting Your Confusing Medication Prescriptions

When your doctor hands you a prescription for a medication, you may think some of it is written in another language—maybe because of its bad handwriting and/or perplexing abbreviations and symbols.

Doctor writing perscription
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Common Medical Prescription Abbreviations 

Many abbreviations on a prescription pertain to how often a person should take a medication, like before a meal, or the route of administration, like inhaled versus by mouth. Some examples include:

  • a.c. or ac ( before meals)
  • b.i.d. or bid (twice daily)
  • t.i.d. or tid (three times daily)
  • h.s. or hs (at bedtime)
  • p.c. or pc (after meals)
  • s.o.s. or sos (if necessary)
  • p.r.n. or prn (as needed)
  • "inh" for inhaled (like an asthma rescue inhaler)
  • "po" for by mouth
  • "SC" or "SQ" for subcutaneous (like an insulin injection)

The problem with medical abbreviations is that they can be misread or misunderstood by pharmacists, leading to a medication error, and this can be harmful to a patient.

Let's face it, bad handwriting is common, and a slip of the finger on an electronic prescription is also not far-fetched.

Banned Medical Abbreviations by JCAHO

 To prevent these medical errors, the Joint Commission on Accreditation of Health Organizations (JCAHO) created a "Do Not Use" list of abbreviations in 2003.

According to JCAHO, for the following abbreviations, doctors must write the full word and not the abbreviation on any order or medication-related document that is handwritten (including computer forms where there is free text) or pre-printed forms.

  • "U" or "u" for "Unit"
  • "IU" for "International Unit"
  • "q.d." or "qd" or "Q.D." or "QD" for daily 
  • "qod" or "q.o.d." or "QOD" or "Q.O.D." for every other day 
  • "MS", "MSO4", or "MgSO4" -- must write out either "morphine sulfate" or "magnesium sulfate"
  • No trailing zeros (e.g. doctors must write out 5mg and not 5.0 mg)
  • Lack of leading zeros (e.g. doctors must write 0.5mg instead of .5mg)

More Examples of Error-Prone Medical Abbreviations and Symbols

In 2005, the Institute of Medical Practices, or ISMP, also created a list of medical abbreviations that can cause errors. This list is much larger that the JCAHO list. A few examples include:

  • "cc" be written as "mL" or "milliliters," as "cc" can be mistaken for "U" for units
  • micrograms should be written as "micrograms" or "mcg" and not "μg"
  • avoiding the symbol "@," as this can be confused for a "2." 
  • avoiding "SC" or "SQ," as "SC" can be mistaken for "SL" (sublingual) and "SQ" as " 5 every"—instead, doctors should write out "subcut" or "subcutaneous"

Bottom Line

In good practice, your doctor should write out medical instructions fully on a prescription, including the medication name, frequency of intake, and route of administration—like Ciprofloxacin 250mg by mouth once daily. This ensures clear communication to the pharmacist and/or nurse and optimizes safety for you as a patient. Of course, if you suspect an error on your prescription please notify your doctor and pharmacist right away—even with the new abbreviation guidelines, errors do occur. Trust your gut and your keen eye.


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Additional Reading
  • Glassman P. Making Health Care Safer II: An Updated Critical Analysis of the Evidence for Patient Safety Practices. Chapter 5. The Joint Commission's “Do Not Use” List: Brief Review (NEW). Rockville: Evidence Reports/Technology Assessments, No. 211, 2013. 
  • Kuhn, I.F. Abbreviations and acronyms in healthcare: when shorter isn't sweeter. Pediatric Nursing. 2007 Sep-Oct;33(5):392-8.