Types of Short Acting Insulins

Insulin is a hormone that helps cells remove glucose from the blood to use as energy. Diabetes occurs when there is little or no insulin in the blood or the body's cells don't react properly to the insulin that is present. Patients with Type 1 diabetes and some patients with Type 2 diabetes have to use an external source of insulin, given by injection. There are several types of insulin, which are classified according to the speed in which the insulin begins working: rapid-acting, short-acting, intermediate, long-acting and mixed. Rapid- or short-acting insulin begins working very quickly after injection.

Rapid-Acting Insulin

• Clear-colored, rapid-acting insulin starts working within 15 to 20 minutes of injection into the body. This type of insulin is most effective at removing glucose from the blood about one hour after injection; rapid-acting insulin has no effect on glucose levels about four to five hours after injection. Since this type of insulin works so quickly, you must eat immediately after injection. Some examples are lispro, insulin aspart and insulin glulisine.

Short-Acting Insulin

• Short-acting insulins should be taken at mealtime. After injection, this clear-colored insulin starts working between 30 to 60 minutes. Its peak effectiveness is two to three hours after injection; it continues to work for up to six hours. Take short-acting insulin about 15 to 30 minutes before eating. Examples of short-acting insulin are "regular" insulin and Velosulin (human insulin).

Mixed Insulin

• This cloudy-looking insulin is a combination of either a rapid-acting insulin or a short-acting insulin and an intermediate acting insulin in a predetermined proportion. This allows you to inject two types of insulin at once. Onset occurs 10 to 30 minutes after injection, depending on the type of rapid- or short-acting insulin used in the combination. Peak effectiveness varies from 30 minutes to 12 hours, depending on the intermediate insulin included. Examples include Humulin 70/30, Novolin 70/30 and Novolog 70/30.

When to Use Short-Acting Insulins

• Your physician will help you select which type of insulin would work best. The type of food you eat and how much alcohol you consume are both factors in the decision. Before choosing a short-acting insulin, you need to decide if you're willing to give yourself multiple injections or check blood glucose levels. If not, other types of insulin may be a better option.

Side Effects

• Insulin can cause a dangerously low blood-glucose level called hypoglycemia if it is used without eating at the appropriate time. Severe hypoglycemia can happen within 15 minutes with some rapid-acting insulins. Insulin use can cause weight gain and a loss of fatty tissue wherever the insulin is injected in the body. Allergic reactions are rare.