Which insulin is the longest-acting among those listed?

• A. Ultralente
• B. Lispro
• C. Regular insulin
• D. NPH insulin

Answer: (A)

Understanding duration of action is what this question is asking. Among these insulins, the rapid-acting one (Lispro) starts quickly and lasts only a few hours, making it suitable for mealtime control but not for long basal coverage. Regular insulin is short-acting and lasts a bit longer than Lispro, roughly five to seven hours. NPH is intermediate-acting, with a noticeable peak and a total duration in the roughly 14–24 hour range. Ultralente is designed as a long-acting preparation; its zinc-insulin suspension slows absorption from the subcutaneous tissue, providing a prolonged, steady effect that can extend across the day and beyond. Because of this prolonged duration, Ultralente has the longest-acting profile among the options.