 Types of insulin differ with respect to their source, how fast they begin to act, and how long their effect persists. Today most people use synthetic brands of insulin, such as Humulin and Novolin, which are identical to natural human insulin. Older insulin brands such as Iletin are extracted from the pancreases of cattle or pigs and differ slightly from human insulin, making them more likely than synthetic types to cause side effects such as skin rash and fat deposits under the skin. With respect to speed of onset and duration of effect, there are prompt, short, intermediate, and long-acting insulins. Lispro (brand name Humalog) is a prompt-acting insulin. It starts to lower blood sugar in about 15 minutes, reaches its peak sugar-lowering effect after 60 to 90 minutes, and stops affecting blood sugar four to five hours after you inject it. You should inject Lispro just before a meal. Regular insulin such as >Humulin R and >Novolin R is defined as short acting. It begins lowering blood sugar from 30 to 60 minutes after you inject it. The peak effect from an injection occurs after two to three hours and the effect lasts for a total of five to seven hours. Lente (>Humulin L, >Novolin L) and NPH (>Humulin N, >Novolin N) are intermediate-acting insulins. They start to work within two to four hours after injection, achieve their peak of activity after four to 12 hours, and last for a total of 14 to 20 hours. Ultralente (>Humulin U) is a long-acting insulin that kicks in approximately six to 10 hours after you inject it. Its peak effect in lowering blood sugar doesn't occur until 14 to 24 hours following injection and it continues acting for a total of 20 to 36 hours. Insulin glargine (>Lantus) is a new form of long-acting insulin. It starts to work within one to two hours and continues acting for about 24 hours. Lantus is different from other forms of insulin in that is does not have a peak effect. Instead, it lowers blood sugar a relatively constant amount during the 24-hour period it is in the body. Many people use more than one type of insulin to control their blood sugar. You shouldn't mix certain types of insulin together in the same syringe, so make sure to check with your doctor or pharmacist first. Some people use premixed combinations of regular and NPH. Examples include >Humulin 70/30, >Novolin 70/30, and >Humulin 50/50. 70/30 insulin is 70 percent NPH and 30 percent regular insulin. 50/50 insulin contains 50 percent NPH and 50 percent regular insulin. These insulins provide the same activity as if you injected NPH and regular insulin separately. But they can be easier to use, since you don't have to measure two separate doses. Sources:
American Diabetes Association Complete Guide to Diabetes. American Diabetes Association, 1997.
Applied Therapeutics: The Clinical Use of Drugs. Applied Therapeutics, 1995.
Drug Facts and Comparisons. Facts and Comparisons, 2001.
Lantus Product Information, Aventis Pharmaceuticals, 2000.
This answer prepared 6/4/01.
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