Journal of the Endocrine Society
Background: Humulin R U-500 is a concentrated human insulin indicated to improve glycemic control in adults and children with diabetes mellitus requiring more than 200 units of insulin per day. R U-500 insulin is five times more concentrated than U-100 insulin.
Clinical Case: A 42-Year-old woman with medical history of depression, hidradenitis, morbid obesity, hypertension, hyperlipidemia, chronic headache, and type 2 diabetes mellitus was on R U-500 insulin, Jardiance, and Victoza. Patient presented with low blood glucose levels. Patient reported that her home insulin regimen is 20 units of R U-500 insulin with meals. Her home glucose diary showed blood glucose levels as low as 30-50 mg/dL. Recent hemoglobin A1c was 6.5%. Of note, the patient was unaware of hypoglycemic symptoms. Upon taking detailed history, and discussing insulin injection technique, it was apparent that the patient was administering insulin correctly. Upon further inquiry, the patient reported not being aware of the specialized R U-500 syringe. Patient expressed unfamiliarity after being shown images of the correct R U-500 syringe. It became apparent that the patient was using a U-100 insulin syringe to draw from R U-500 insulin vial which means she was receiving an incorrect dosage. Filling the U-100 syringe to the 20-unit mark with R U-500 insulin will deliver 100 units of R U-500 insulin which puts the patient at risk of severe hypoglycemia. During hospital stay, U-500 R insulin, Victoza, and Jardiance were stopped, the patient was started on basal and bolus insulin regimen, and blood glucose levels were monitored with meals and at bedtime. Blood glucose levels improved to 140-180 mg/dL. Upon hospital discharge, the patient was encouraged to switch to R U-500 KwikPen as this will be more accurate and safe.
Conclusion: The U.S. Food and Drug Administration approved a dedicated syringe for the administration of Humulin R U-500 insulin, which is now the only device approved for use with U-500 insulin vial. Do not switch between types of syringes because it may increase the risk of dosing errors.
Rizwan T, Alchalabi M, Arora G, Qureshi UN, Qureshi F. Risk Of Life Threatening Hypoglycemia When Using U-100 Insulin Syringes To Administer R U-500 Insulin. Journal of the Endocrine Society. 2023; 7(Supplement 1). doi: 10.1210/jendso/bvad114.1031.