Which of the following is a rapid-acting insulin?

Lispro is classified as a rapid-acting insulin because it is engineered to have a quick onset of action, typically beginning to work within 15 minutes after injection, peaking in about 1-2 hours, and having a duration of action of around 3-5 hours. This rapid response makes it particularly beneficial for controlling blood glucose levels during mealtime, allowing for more flexibility and precise management of postprandial hyperglycemia.

In contrast, glargine and detemir are both long-acting insulins, designed for a gradual and extended release to maintain baseline insulin levels throughout the day. NPH insulin is an intermediate-acting formulation that has a more prolonged onset and peak when compared to rapid-acting insulins. Therefore, among the given choices, lispro is the only option that fits the category of rapid-acting insulin.