What is regular insulin for diabetes?

Regular insulin starts working a half hour after you take a shot. It works hardest from 2 to 3 hours after your shot and stays in your blood from 3 to 6 hours.
Gary Scheiner
Endocrinology Diabetes & Metabolism

Regular or "R" insulin is an older form of mealtime insulin. It does not work as quickly as the rapid-acting insulin analogs (lispro, aspart, glulisine) that are commonly used today. Hence, blood sugar levels tend to spike quite high and then drop quickly a few hours later. 

Of note, certain brands of Regular insulin (Humulin R, Novolin R) are structurally identical to human insulin and are less likely to cause allergic responses at the injection site compared to rapid-acting insulin analogs. Regular insulin is sometimes also used by those with impaired digestion (gastroparesis) to provide a better match of the insulin's peak to food's digestion.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.