If you're waiting for a patient's insulin pen to arrive from the pharmacy, don't be tempted to "borrow" an insulin pen from another patient. Putting on a new disposable needle and giving an injection to your patient with another patient's insulin pen could be unsafe. Biologic contamination of insulin can occur even when you don't aspirate before giving an insulin injection.
Although cases of cross-contamination haven't been reported, several studies have pointed out the risks of pen sharing among patients. Hemoglobin was found in 6 out of 146 cartridges in one study, and noninert materials such as epithelial cells were found in 58% of cartridges in another study. The studies' authors state that air bubbles can enter the insulin cartridge after injection unless the needle is removed, suggesting that biologic materials could also enter the cartridge if the needle isn't removed.
Insulin pen manufacturers instruct users not to share pens and to remove the needle immediately after injection so air doesn't enter the cartridge. Ongoing education-for patients and health care providers-is key to using insulin pens successfully and safely.