Insulin lispro (Humalog) — rapid-acting insulin analog

Mechanism and characteristics

Lispro’s molecular change involves swapping two amino acids near the end of the insulin B-chain; this alteration reduces self-association into hexamers, so the insulin is absorbed more rapidly after subcutaneous injection. Clinically, that translates into a faster onset and a shorter duration of activity compared with regular insulin. It is available in prefilled pens and vials and may be used in continuous subcutaneous insulin infusion (insulin pump) systems.

Uses and administration

Patients typically inject lispro shortly before eating, though timing can be individualized by clinicians. Dosage is adjusted based on carbohydrate intake, current blood glucose, and insulin sensitivity. Health professionals may combine lispro with longer-acting basal insulin to provide both mealtime and background glucose control. For basic information about diabetes and insulin, see diabetes resources and insulin therapy overview. For information on LADA, see LADA resources.

Side effects and precautions

Like other insulins, the most common adverse effect is hypoglycemia if dose, meal intake, or activity are not balanced. Other possible effects include injection-site reactions, weight gain, and rarely allergic responses or lipodystrophy with repeated injections. Doses must be individualized; clinicians advise caution during illness, pregnancy, or changes in routine. Storage and handling directions should be followed to preserve potency.

History and comparisons

Lispro was one of the first rapid-acting analogs to become widely available and was approved for clinical use in the mid-1990s. It is part of a class that also includes insulin aspart and insulin glulisine; these analogs share the goal of improving postprandial glucose control compared with regular human insulin. Choosing among analogs depends on individual response, device compatibility, cost, and clinician judgment.