Short answer: Regular insulin has a half-life of about 1.5 hours (Humulin R, under the skin). Levels peak about 2 hours (Humulin R); 1.5 to 2.5 hours (Novolin R) after a dose. People vary, so treat these as estimates.
Regular insulin is lab-made human insulin with nothing added to change its timing: a short-acting insulin injected about 30 minutes before meals. It is sold as Humulin R and Novolin R (both 100 units/mL), and as Humulin R U-500, a five-times-stronger form for people who need more than 200 units a day.
Also known as: Humulin R, Novolin R, Humulin R U-500, insulin human regular.
Humulin R U-100 (100 units/mL) comes in 10 mL and 3 mL vials. Novolin R is U-100 in a 10 mL vial and a 3 mL FlexPen. Humulin R U-500 (500 units/mL) comes in a 3 mL KwikPen holding 1,500 units, which dials in 5-unit steps up to 300 units and shows actual units; the label says it is never drawn from the pen into a syringe.
The labels approve regular human insulin to improve blood sugar control in adults and children with diabetes; Humulin R U-500 is only for people who need more than 200 units of insulin a day. Label timing: injected under the skin about 30 minutes before meals, usually with an intermediate- or long-acting insulin; U-500 is usually injected two or three times a day. The dose is set for each person, with no fixed starting dose. U-100 can be given into a vein only under medical supervision, with checks of blood sugar and potassium. The Novolin R label says it is not recommended in insulin pumps, and U-500 is not used in a pump or a vein. The labels give no missed-dose rule.
No regular insulin label has a boxed warning. Low blood sugar is the most common side effect of every insulin, and severe lows can cause seizures or death. The labels also warn: never share a pen, cartridge or syringe, even with a new needle; changes in insulin type, maker, strength or injection site are made under medical supervision with more glucose checks; insulin mix-ups have happened, so the label is checked before each injection; insulin can lower potassium; and heart failure can worsen when insulin is used with a thiazolidinedione such as pioglitazone. The Humulin R U-500 label adds that severe lows may develop as late as 18 to 24 hours after an injection. The U-100 labels give no trial percentages; they list injection site reactions, rare severe allergy, low potassium, skin pits or thickening, swelling and weight gain. See side effects of Humulin R, Novolin R and Humulin R U-500; dosing schedules for Humulin R, Novolin R and Humulin R U-500; storage for Humulin R, Novolin R and Humulin R U-500; and Novolin R vs Humulin R, Humulin R vs Humalog and Novolin R vs NovoLog. Glossary: regular insulin and concentrated insulin.
The Humulin R label says that with doses of 0.05 to 0.4 units/kg under the skin, the effect begins about 30 minutes after a dose (range 10 to 75 minutes), is strongest at about 3 hours and ends after about 8 hours (range 3 to 14). The median apparent half-life was about 1.5 hours (range 40 minutes to 7 hours), and in type 1 diabetes levels peaked at about 2 hours. In obese people given 50 or 100 units, the effect lasted about 18 hours. The Novolin R label says the effect begins about 30 minutes after a dose, is strongest at 1.5 to 3.5 hours and ends at about 8 hours, with peak levels at 1.5 to 2.5 hours.
Numbers shown are taken from the source above. Half-life varies from person to person.
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