Lispro is a rapid-acting insulin used to help control blood sugar levels in people with diabetes. It works quickly after injection, usually within 15 minutes, and its effects can last for about 2 to 4 hours. This makes it particularly useful for managing blood sugar spikes that occur after meals. Lispro is often taken just before or after eating to mimic the natural insulin response of the body. It is available in various forms, including vials and pre-filled pens, and is typically prescribed alongside a comprehensive diabetes management plan that may include diet and exercise.