Updated July 25, 2006

Understanding Insulin

by Laura Hieronymus, M.S.Ed., A.P.R.N., B.C.-A.D.M., C.D.E., and Patti Geil, M.S., R.D., C.D.E.

Premixed insulins. Premixed insulin preparations contain intermediate-acting insulin that is mixed with either rapid- or short-acting insulin in varying percentages. The advantage to using a premixed preparation is that you don’t have to mix the insulins yourself when drawing up an injection or take two injections rather than one.

All of the insulin analogs require a prescription from a physician for purchase. Human insulin does not require a prescription for purchase in some states; however, a prescription is usually necessary for insurance coverage. Use of insulin therapy should always follow a physician’s recommendation and prescription.

Challenges of insulin therapy
Insulin may be a lifesaver for people with Type 1 diabetes and may offer the best chance of achieving optimal blood glucose control for many with Type 2, but it can be a challenge to use. The body’s need for insulin is based on many things—including body weight, stage of growth, food intake, physical activity, use of certain drugs, and physical or mental stress—all of which can change from day to day.

When there is too much insulin in the bloodstream relative to the body’s needs, hypoglycemia, or low blood glucose, results. Hypoglycemia can occur as the result of skipping or delaying a meal, taking more insulin than is necessary to control blood glucose levels, engaging in unusual or more frequent physical activity than normal, and consuming alcohol. People who use insulin should be aware of the signs and symptoms of hypoglycemia, as well as how to treat it. (See “Treating Hypoglycemia.”)

Many people gain weight when they start insulin therapy, usually because their bodies are now absorbing glucose that was previously exiting the body in the urine. For people who had lost a lot of weight because of their diabetes, the weight gain may be welcome, but for many, it is not. To slow any weight gain and maintain a healthy weight, it’s necessary to consume only as many calories as your body needs, given your level of physical activity. A registered dietitian can help you determine what and how much to eat to maintain a healthy weight and optimal blood glucose control. It’s also worth noting that weight loss (through burning more calories than are consumed) can lower insulin needs, while weight gain can increase it.

It’s possible to have an allergic reaction to insulin. Symptoms of a local reaction at the injection site include slight swelling, itching, and redness. Local reactions can occur as the result of preservatives used in the insulin (not the insulin itself), the material used in the needle, products used to cleanse your skin prior to injection, or using an injection technique that injures the skin. Determining the cause is important. Let your diabetes care team know if any of these symptoms occur. Symptoms of a more serious, systemic allergic reaction include shortness of breath or wheezing, fast heart rate, clamminess, and a rash that occurs all over your body. If any of these occur, notify your physician immediately.

Skin changes due to repeated insulin injections, such as slight pitting or areas of thickened skin, are rare but possible. If you notice that your skin is changing in the area you inject insulin, consult your diabetes care team. A change in injection technique or needle size may solve this problem.

When insulin doses are inadequate relative to the body’s needs, high blood glucose results. Common causes of high blood glucose include not taking enough insulin for the amount of food eaten and physical stress such as an illness or infection. Very high blood glucose can lead to serious consequences such as diabetic ketoacidosis or hyperosmolar hyperglycemic state, both of which usually require hospitalization. Chronically elevated blood glucose, even when it doesn’t cause an acute crisis, can damage the blood vessels and nerves in the body over time. Your diabetes care team can help you learn to keep your blood glucose in target range and develop a plan for responding to high blood glucose if it occurs.

Also in this article:
Treating Hypoglycemia

Patti Geil and Laura Hieronymus are certified diabetes educators and diabetes health consultants in Lexington, Kentucky. They are part of the education team at an American Diabetes Association–recognized education service at Drs. Borders & Associates, PSC. The authors would like to acknowledge the expertise and contribution of their colleague, Stacy Griffin, Pharm.D., R.Ph.

More articles on Insulin

Statements and opinions expressed on this Web site are those of the authors and not necessarily those of the publishers or advertisers. The information provided on this Web site should not be construed as medical instruction. Consult appropriate health-care professionals before taking action based on this information.