Which syringe would you select to administer Humulin R U-500 65 units?

Syringe 1: This U-100 insulin syringe with a 30-unit capacity is inappropriate for this task because the required dose of 65 units exceeds its maximum capacity. This syringe is calibrated for U-100 insulin, and using it for U-500 insulin would lead to a potentially fatal overdose. Syringe 2: This is a U-100 insulin syringe with a 50-unit capacity. Its capacity is insufficient for the 65-unit dose. Critically, using a U-100 syringe for U-500 insulin would result in a significant medication error and a massive overdose. Syringe 3: This is a U-100 insulin syringe with a 100-unit capacity. Although the 65-unit dose fits within its capacity, the unit markings are based on U-100 concentration, so drawing to the 65-unit line would actually administer 65 U-100 units, which is a severe overdose of U-500 insulin. Syringe 4: This is a small-volume syringe calibrated in milliliters, not U-100 units. The proper dose of 65 units of U-500 insulin is calculated as 65 units / 500 units per mL = 0.13 mL. This syringe can accurately and safely measure this specific volume, making it the appropriate choice to prevent a dosing error.