Rx Update: August 2002

It's Official: Don't Use "U" for "Units"

Mary Ross, R.Ph., M.B.A., Barbara Mutnick, R.Ph., M.H.P., Joan Murhammer, R.Ph.
Peer Review Status: Internally Reviewed

One of the major causes of medication errors is the ongoing use of potentially dangerous abbreviations and dose designations. While many drug name and medical abbreviations have been associated with medication errors, the designation "U" for unit/units has been especially problematic. This was noted by the Joint Commission on the Accreditation of Healthcare Organizations (JCAHO) in its September, 2001, Sentinel Event ALERT entitled, "Medication Errors Related to Potentially Dangerous Abbreviations.1 In this document the JCAHO points out that when "U" is poorly handwritten, it can often look like a zero (0), potentially leading to ten-fold overdoses or greater. There have been numerous case reports from around the U.S. where the root cause of sentinel events related to insulin dosage has been the interpretation of a "U" as a zero (e.g., "6 U" mistakenly interpreted as 60 units). See examples of potentially misread orders below.

Several other national safety organizations, including the Institute for Safe Medication Practices (ISMP) and the National Coordinating Council for Medication Error Reporting and Prevention (NCCMERP), have also recommended that "U" not be designated as an approved medical abbreviation for unit/units.2, 3 These organizations point out that besides the confusion with zero, other error reports have described situations in which "U" has been misinterpreted as "4" or "cc."

Because of the safety concerns outlined above, the Pharmacy and Therapeutics Subcommittee and the Health Information Management Subcommittee have approved the deletion of the abbreviation "U" for unit/units from the UIHC's list of Approved Medical Abbreviations. Prescribers and other clinicians should spell out the complete word unit (or units) when ordering medication or other treatments designated in this manner. Prescribers will be notified to clarify orders using the "U" designation.

handwriting examples
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  1. "Medication Errors Related to Potentially Dangerous Abbreviations," JCAHO Sentinel Event Alert, Issue 23, September 2001, at www.jcaho.org .
  2. ISMP Medication Safety Alert!, May 2, 2001, www.ismp.org.
  3. "Recommendations to Correct Error-Prone Aspects of Prescription Writing," NCCMERP Council Recommendation, adopted Sept. 4, 1996, at www.nccmerp.org (under Council Recommendations).

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