Dosage errors common with Humulin R U-500 insulin

The Institute for Safe Medication Practices (ISMP) continues to receive reports of dose measurement confusion with Humulin R U-500 concentrated insulin injection, according to a recent safety alert from the agency.

For example, in one case, a physician prescribed U-500 for a patient and provided instruction to the patient and his wife on how to calculate and measure the correct dose using a U-100 insulin syringe. “However, the staff at the community pharmacy provided training to the patient on how to measure his dose using a tuberculin syringe, introducing the possibility of 5-fold dosing errors,” ISMP wrote in its June, 2013 ISMP Medication Safety Alert! Community/ Ambulatory Care Edition.

“It is critical that prescribers, pharmacists, and ultimately, the patients are all on the same page when it comes to how U-500 insulin is to be prescribed and measured. Otherwise, patient harm can occur,” the ISMP alert warned.

If U-100 insulin syringes are used, it is “extremely important” to explain the amount of Humulin R U-500 insulin to be administered in both the actual dose and with specification of unit markings on the U-100 syringe, according to ISMP. If tuberculin syringes are used, since their markings are in volume (mL), the actual amount of Humulin R U-500 should be explained in both actual dose and with specifications of “volume (mL) markings” on the tuberculin syringe.

“It is also important to patients to notify other healthcare professionals of the type of syringe they are using to measure their insulin, especially when treated in an emergency department or admitted to a hospital,” ISMP wrote.