Home Diabetes Glossary lispro insulin lispro insulin Wednesday,January 4, 2023 ByDiabetesCare.net by DiabetesCare.net | Jan 4, 2023 | 0 comments (LYZ-proh): a rapid-acting insulin. On average, lispro (Humalog) insulin starts to lower blood glucose within 5 minutes after injection. It has its strongest effect 30 minutes to 1 hour after injection but keeps working for 3 hours after injection. Submit a Comment Cancel replyYou must be logged in to post a comment.