All patients with Type 1 diabetes must use insulin. Because the insulin dose is determined by blood glucose levels, you and your patient must monitor those levels with particular care.People with Type 2 diabetes produce some insulin, but generally not enough to lower their blood glucose levels. If other treatments can’t control their blood glucose levels, they may also require insulin. Some patients with Type 2 diabetes may require insulin only temporarily during times of stress.

All insulins are administered subcutaneously. Regular insulin may be administered I.V. Because of its protein nature, insulin must be administered by injection. Given orally, it would be digested and destroyed in the GI tract.

Insulin restores the cells’ ability to use glucose as a source of energy, but researchers don’t know exactly how. Insulin is involved in cell membrane transport, so it increases cell growth and the metabolism of carbohydrates, proteins, and fats.

Insulin maintains blood glucose levels through several mechanisms. In the liver, insulin decreases the breakdown of glycogen, prevents the formation of new sources of glucose from amino acids, and prevents the formation of ketone bodies. At the same time, insulin increases the synthesis and storage of glycogen and fatty acids and decreases the breakdown of fat in adipose tissue. Insulin also enhances the use of amino acids and decreases the breakdown of protein in muscle tissue.

Types of Insulin

Insulin is classified as rapid-acting, intermediate­acting, or long-acting, depending on its onset, peak, and duration of activity .

Most rapid-acting insulins begin working in 30 minutes and reach their peak in 2 to 5 hours. Their duration of action is 6 to 8 hours. One form of rapid-acting insulin, lispro, begins working in 5 to 15 minutes and reaches its peak in 30 to 90 minutes. Its duration of action is 2 to 4 hours. Rapid-acting insulins compensate for the meals eaten after injection. For some patients, using lispro before a meal improves postprandial glycemic control and reduces the risk of hypoglycemia because of its short duration of action. Other rapid-acting insulins include regular and Semilente insulin.

Intermediate-acting insulin starts working in 1 to 3 hours and reaches its peak in 4 to 15 hours. Its duration of action is 18 to 24 hours. It may be given in split doses, before meals, but the patient must eat at the time of peak action to prevent hypoglycemia. Intermediate-acting insulins include neutral protamine Hagedorn (NPH) and Lente insulins. NPH insulin contains protamine sulfate, a protein derived from fish that can cause an allergic reaction. Lente insulin is a good choice for people sensitive to protamine.

Long-acting insulin starts to work in 4 to 6 hours and reaches its peak in 8 to 20 hours. Its duration of action is 24 to 28 hours. Ultralente, the only long-acting insulin, gives patients a consistent insulin effect.

Some patients need a mixture of insulins. One that’s rapid-acting, such as regular insulin, for a fast onset and one that’s intermediate-acting, such as NPH, for a longer duration of action. These insulin mixtures are available in premixed bottles. For example, NPH and regular insulin are available in 70/30 and 50/50 mixtures. The premixed bottles are especially useful for elderly patients or patients with vision loss.

Sources of Insulin

Extracts of beef and pork pancreas were once the only sources of insulin. Beef insulin is no longer used, except in some beef and pork mixtures, and pork insulin is rarely used. Today, human insulin, which is derived from recombinant deoxyribonucleic acid technology, and the human analog lispro are the two forms most commonly used. Insulin from all sources appears to be equally effective at controlling blood glucose levels. However, human insulin causes less lipoatrophy, less antibody production, and fewer allergic reactions. And it’s absorbed faster than pork insulins.

Changing between pork and human sources of insulin can disrupt blood glucose levels and require dosage adjustments. People who need insulin only temporarily-a patient with Type 2 diabetes undergoing surgery, for example-should use human insulin.

Indications and Contraindications

Insulin is essential for everyone with Type 1 diabetes. Type 2 patients may need it if diet, exercise, weight control, and oral antidiabetic drugs haven’t been effective. They may also need it during periods of stress involving fever, severe trauma, infection, major surgery, DKA, and HHNK syndrome. Insulin therapy is recommended for women with gestational diabetes if diet alone doesn’t control blood glucose levels.

Adverse Effects and Interactions

Hypoglycemia is the most common adverse effect of insulin therapy. Other adverse effects include lipodystrophy, insulin resistance, and, in rare cases,insulin allergy.

The two types of lipodystrophy are lipoatrophy and lipohypertrophy. Lipoatrophy, which is caused by animal insulins, results from the breakdown of adipose tissue at the injection site or in areas away from the injection site and causes a loss of fatty tissue. Dimpling may result from an injection with an impure insulin preparation or may be an immune response. Treatment includes injecting human insulin or steroids around the area of breakdown.

Lipohypertrophy occurs after repeated injections into the same site. The skin in the hypertrophied area eventually loses sensation. Because the hypertrophied area is an accumulation of fatty tissue, tell your patient not to use it for additional injections because the insulin will be absorbed erratically.

Insulin resistance results from the formation of antibodies that bind to insulin, making it inactive. Patients with cirrhosis of the liver or a disease of the endocrine glands may also develop insulin resistance. The patient becomes unresponsive to usual doses and may need as much as several hundred units of insulin a day. Changing from animal to human insulin or purified pork insulin may correct the problem. Or a corticosteroid may treat it. For obese patients who have nonimmunologic insulin resistance, the treatment is weight loss.

A patient with an insulin allergy may develop redness, swelling, aching, and pruritus at the injection site 4 to 8 hours after the injection. Or she may develop systemic allergic reactions.

Insulin products derived from animal sources cause allergies in some patients. The physician will probably substitute human insulin.

Some people are allergic to the insulin preparations or to the preservatives in the solution. Other people may be hypersensitive to the skin­cleansing agent used before injectionShould . Some patients are allergic to the latex in the stopper of the vial or in the plunger of the syringe. If any allergic reactions occur, your patient should contact her physician immediately.

Systemic allergic reactions to insulin are uncommon, especially with purified insulin preparations. If an anaphylactic reaction occurs, however, it may be life threatening. The signs and symptoms include rash, shortness of breath, tachycar­dia, hypotension, diaphoresis, angioedema, and anaphylaxis. Patients with severe systemic reactions should have a skin test before they begin using a new insulin preparation.

Several drugs can increase or decrease the action of insulin . No foods interact with insulin. However, to achieve optimal glycemic control, patients should follow their prescribed meal plan in conjunction with their insulin prescription.

Administration

The dosage and number of daily insulin injections depend on each patient’s circumstances. Many patients are on an insulin regimen that requires different kinds or mixes of insulin. The physician considers the time of insulin administration, diet, and exercise when determining dosages. After initial insulin dosages have been determined, monitor the effects of the insulin.

Your patient will inject insulin subcutaneously with a short (1/2 inch), small-bore (27, 28, or 29 gauge) needle .

The rate of absorption of insulins other than lispro varies with the injection site. Insulin is absorbed from the abdomen faster than from any other site. The upper arm provides the next most rapid absorption, followed by the thigh and but­tock. Instruct your patient not to administer insulin within a 2-inch radius of the umbilicus to prevent injection into a blood vessel. Because the rate of absorption of insulin changes with the injection site, patients should rotate injection sites within one area, such as the abdomen, before moving to another, such as the upper arm.

Body temperature also affects absorption. Increased blood flow from sitting in a sauna, having a fever, or exercising a muscle causes insulin to be absorbed more quickly than usual.

Storage: Tell your patient that she can keep unopened bottles of insulin in the refrigerator for up to 3 months. She shouldn’t freeze the insulin because freezing can cause clumping. A bottle in current use can be stored at room temperature, out of direct sunlight and extreme heat, for up to 1 month. Prefilled syringes may be stored in the refrigerator vertically (needle up) for 1 to 2 weeks. Instruct her to check the expiration date on the insulin bottle periodically and to discard the insulin when it expires.

Injection: When teaching your patient how to inject insulin, first instruct her to roll the bottle of insulin suspension gently between her hands so that the contents don’t form bubbles or foam. If a bottle of insulin contains granules or clumps after mixing, instruct her to discard the bottle. Because regular insulin is clear, the bottle doesn’t have to be rolled before use. Instruct your patient to discard the bottle of regular insulin if it’s discolored or cloudy or contains granular material.

Next, instruct your patient to stretch the skin at the injection site and insert the needle at a 90­degree angle .

Several new alternatives to syringes simplify insulin injection. Spring-operated insulin pens,which metal container with a are preloaded with bottles of insulin, are convenient and accurate. The cartridges, which don’t have to be refrigerated, supply enough insulin for 3 to 5 days. Using the pen, however, requires skill and dexterity. Patients with impaired vision can buy devices that facilitate drawing up and administering insulin with a syringe, including syringe magnifiers, needle guides, bottle stabilizers, and nonvisual insulin measurement systems.

Disposal: Advise your patient to dispose of needles and lancets in a hard plastic container, such as an empty detergent bottle, or a tightly secured lid. If the patient uses coffee cans to dispose of needles, caution her to reinforce the plastic lid with several layers of duct tape. Some drugstores sell commercial containers like the ones used in hospitals.

Tell your patient to put needle containers in the regular trashnever with recyclables. If she lives in an area with a depot system for dropping off used syringes, encourage her to do that.

Insulin Pumps: Instead of using subcutaneous injections, some patients can use insulin-pump therapy, a method of insulin administration that more closely mimics the normal function of the pancreas. To be a candidate for the insulin pump, a patient must have Type 1 diabetes, be able to monitor her own blood glucose levels, and be able to operate the pump. Patients using pump therapy also must be highly motivated; they’ll have to monitor their blood glucose levels at least four times a day and keep careful records to help evaluate their therapy.

The battery-powered pump contains a syringe and a computer chip that stores information for insulin administration. To administer insulin, the patient attaches an infusion set with a small catheter to the pump. She then inserts the catheter into her abdomen, arm, or thigh. She can wear the pump 24 hours a day but should change the injection site every 72 hours. She should also change the site when it becomes inflamed or painful, or whenever the system leaks or becomes clogged.

Using the pump provides several benefits. Because blood glucose levels can be more tightly controlled, glycosylated hemoglobin levels and the number of hyperglycemic episodes can be reduced. The pump may also help lower the number of congenital birth defects in children who are born to mothers with diabetes. Insulin-pump therapy also may help delay the progression of microvascular and macrovascular complications and neuropathy.