Insulin errors--abbreviations will
get U in trouble
From the Aug. 13,1997 Issue
PROBLEM: The cause of many insulin errors is the use
of abbreviations in written orders. The abbreviation "U" for
"units" has often been misread as a zero, resulting in serious,
tenfold overdoses. Recently, we heard about three new cases
that illustrate other problems when abbreviations are used
in insulin orders.
In one case, a home health nurse administered 41 units of
regular insulin to a patient after reading a written order
for "Regular insulin 4 IU" in a chart at the patient's house.
Fortunately, the patient was not harmed. A student nurse,
aware that the correct order was for 4 units because she had
checked the master chart at the home health care office, questioned
the amount after the dose had already been given.
Another case involved a nurse who read an order for "Insulin
SC NPH 15U AM + 6 units PM" as insulin SC NPH 15 units in
the morning and 46 units in the evening. When she called the
physician to question the high evening dose, the physician,
without thinking, said that that was correct. After the dose
was given, the patient became hypoglycemic but recovered with
Finally, a pharmacist received an order for Humulin®
U (insulin zinc suspension extended, Ultralente). The pharmacist,
who was accustomed to seeing orders for Humulin N (isophane
insulin suspension, NPH), processed the order as Humulin N.
However, he realized the error before the medication was dispensed.
SAFE PRACTICE RECOMMENDATION:In the first situation,
if "units" had been written rather than the abbreviation "IU"
("international units"), the proper dose probably would have
been given. In the second case, the plus sign is sometimes
seen as a "4" (figure 1), which is why it should not be used.
Also, the two insulin orders should have been written as separate
orders on separate lines, rather than continuing the order
together on the second line. Finally, Ultralente is not a
commonly used insulin, so the tendency to see the more familiar
"N" in the handwriting is understandable (figure 2). Because
it is less common, it is important that the full name, Ultralente,
be written out. Unfortunately, Lilly's labeling of insulin
vials invites this shortcut (figure 3) by promoting use of
the "U" or "N." To reduce the potential for errors, it is
best to refer to these insulins as isophane insulin, Ultralente
Before medications like insulin are given, an independent
double-check should be performed by another practitioner.
In the first case, the student nurse could have provided that
double-check. In a home health setting, the patient or a family
member can serve as the double-checker when no one else is
available. It also bears mentioning again that abbreviations
should not be accepted in orders written for insulin-there
is simply no room for interpretation. Finally, prescribers
must recognize the need for good communication skills. If
a pharmacist or nurse mentions that they think something is
wrong, the prescriber must listen carefully to what they are
saying. Since errors in dosing can cause significant patient
harm, insulin ordering and administration must be handled
in a consistent way, with extraordinary care. (D,P,N,Q)