Insulin helps maintain blood sugar levels in people who have type I diabetes, and in many people with type II diabetes, as well, according to the Mayo Clinic. There are many different types of insulin to meet the particular needs of people with diabetes.
Rapid-acting Insulin
This type of insulin is absorbed quickly---it starts working in approximately 15 minutes---but it lasts only 2 to 5 hours (see Reference 1). Novolog and Humalog are two types of this kind of insulin, according to the National Diabetes Information Clearinghouse (see Reference 2).
Short-acting Insulin
Short-acting insulin starts working within 30 to 60 minutes, but the effects do not last as long as other forms of insulin; this type only lasts for approximately 3 to 8 hours (see Reference 1). Two types of short-acting insulin are Humulin R and Novolin R (see Reference 2).
Intermediate-acting Insulin
This type of insulin takes 1 to 4 hours to start working, and lasts 12 to 18 hours, according to the Mayo Clinic. Examples of intermediate acting insulin include Humulin N and Novlolin N (see Reference 1).
Long-acting Insulin
This type of insulin takes anywhere from 1 to 10 hours to start working, but it delivers a steady stream of insulin for up to 24 hours (see Reference 1). Levemir and Lantus are two kinds of long-acting insulin (see Reference 2).
Considerations
In addition to the types of insulin mentioned, your doctor might prescribe various kinds of insulin to use throughout the day, or pre-mixed insulin varieties, according to the Mayo Clinic (see Reference 1).
