What type of insulin acts the quickest in lowering blood sugar levels?

Rapid-acting insulin is designed to act quickly, typically beginning to lower blood sugar levels within about 15 minutes after injection. This type of insulin closely mimics the body's natural insulin response to meals, making it particularly effective for controlling postprandial (after meal) blood glucose spikes.

It is often used by individuals with diabetes to manage their blood sugar levels in relation to carbohydrate intake, providing flexibility to inject it right before or even after a meal. The speed at which rapid-acting insulin works helps prevent hyperglycemia that can occur after eating.

In contrast, long-acting insulin has a slower onset and maintains a baseline level of insulin in the bloodstream over an extended period, making it useful for consistent blood sugar control but not for immediate effects. Intermediate-acting insulin has a longer onset time compared to rapid-acting insulin but is shorter than long-acting, while pre-mixed insulin combines different types for a more comprehensive approach but does not act as quickly as rapid-acting insulin on its own.