Tips to avoid insulin pen mix-ups.


A pharmacist recently heard from two people who mixed up their insulin pens and gave themselves the wrong insulin. First, a 67-year-old man with type 2 diabetes had been taking the long-acting insulin, Tresiba (insulin degludec), 70 units once daily. Because his blood sugar remained high, the man’s doctor also prescribed a rapid-acting insulin, Humalog (insulin lispro) to take with the first bite of dinner. Both of these insulins came in pens. One day, he accidentally took 70 units of the rapid-acting Humalog (which is a very large dose of rapid-acting insulin) instead of the long-acting Tresiba. He immediately realized the mistake and called the Poison Control Help line (1-800-222-1222). He had to check his blood sugar every 15 minutes for several hours and eat and drink sugary foods and beverages during this time to keep his blood sugar from dropping too low (hypoglycemia).

In another case, a 49-year-old man with diabetes was supposed to take rapid-acting insulin, Humalog, 30 units 3 times a day with meals, and long-acting insulin, Tresiba, 60 units once daily. He inadvertently took Tresiba 30 units with his morning meal instead of Humalog. His blood sugar rose way above normal (300 mg/dL), and the man realized he had taken the wrong insulin. His high blood sugar level (hyperglycemia) eventually came down to within normal limits and he had no other problems.

Mix-ups between these two pens are often caused by their similar appearance. Even though Humalog and Tresiba insulin pens are made by different manufacturers, they both are similarly shaped, blue pens, although they have different label colors. Mix-ups can happen more easily when a person has impaired vision.

Here’s what you can do: To avoid this type of mistake, ask your pharmacist to include a special sticker on the pen with the name of the insulin and the dose. Since insulin does not need to be kept in the refrigerator after opening, the pens can be stored in the specific physical locations where they will be administered. For example, keep Tresiba in the bedroom since it is taken once a day in the morning, and keep Humalog in the kitchen or dining room since it is taken with meals. Make sure all medicines are stored up and away and out of sight and reach of children. Also consider using adhesive tape, a rubber band, or a hair tie wound around one of the pens to differentiate the insulin types.

Created on February 1, 2021

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