Also called short-acting insulin, regular human insulin, insulin R, human insulin injection · Reviewed
Definition:Regular insulin is short-acting human insulin, the R in Humulin R and Novolin R. NIDDK lists its onset at about 30 minutes, its peak at 2 to 3 hours and its duration at 3 to 6 hours. It is slower to start and lasts longer than rapid-acting insulin.
What the labels say
Humulin R U-100 is injected under the skin approximately 30 minutes before meals and is generally used with an intermediate or long-acting insulin.
It may be mixed in a syringe only with Humulin N, drawing Humulin R in first and injecting right away.
It can be given into a vein, but only under medical supervision with close checks of blood sugar and potassium. Given that way, the label says its effect begins at about 10 to 15 minutes and ends at a median of about 4 hours.
An opened or unopened vial can be kept at room temperature for 31 days in total.
Humulin R U-500 is the same insulin at five times the strength, for people who need more than 200 units a day; see concentrated insulin.
Side effects on the label
Low blood sugar is the most common reaction. The labels also list injection site reactions, skin pits or thickening, weight gain, swelling and low potassium. Neither Humulin R nor Novolin R has a boxed warning.
Why it matters for your log
Regular insulin and rapid-acting insulin are both used at meals, but with different timing. Logging the product name with each dose keeps the two apart if a prescription changes from one to the other.
General education drawn from labels and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your product are the final word.