Insulin is a hormone that treats diabetes by controlling the amount of sugar (glucose) in the blood. When it is made in the laboratory, it is either derived from pigs or is genetically engineered to be identical to human insulin.

People who need insulin therapy include:

• Type 1 diabetics - insulin in the only medication that can be used to control the increases that occur in Type 1 diabetics,

• Type 2 diabetics - Insulin MAY be used alone on in combination with other medication. Often, Type 2 diabetes can be managed with only oral medications,

• Women with gestational diabetes - oral diabetes medications are not normally used in pregnant women.

Types of Insulin

There are a number of types of insulin that are used to treat diabetes. They are classified by how quickly they start to work and how long their effects last. The types of insulin include:

• Short-Acting insulin works much faster than intermediate- or long-acting insulin so it is used around mealtime. Short-acting insulin should be taken about 30-45 minutes before eating; it peaks at about two to three hours and can work for up to six hours.

• Intermediate-Acting insulin is mixed with a substance that makes the body absorb the insulin more slowly. It takes longer to work and stays in your body for a longer time. NPH is a type of intermediate-acting insulin that usually begins to work within two to four hours after injected. It peaks within four to ten hours after injection and keeps working for 10-16 hours.

• Long-Acting insulin starts to work in six to ten hours and can stay in the body for 20 or more hours. It is usually taken in the morning or before bed.

• According to the American Diabetes Association, short-acting inhaled insulin may be a good alternative to help control blood glucose levels for Type 1 diabetics who cannot or will not administer multiple daily insulin injections. Several products have been created in laboratories and have shown success at controlling blood glucose levels, but only one has been approved for use, and that one is only approved for adults. In clinical trials, the approved inhaled insulin, Exubera, managed blood glucose levels as well as injected fast-acting insulin. However, inhaled insulin has limitations. You need to inhale a lot of insulin to get the amount your body needs since only a small percentage of the inhaled insulin actually reaches the bloodstream and lowers blood glucose. There is also the question about the safety of delivering insulin to the lungs.

Your doctor will prescribe the insulin that is best suited to control your diabetes.

Other Medications

The medication Symlin is sometime used in addition to insulin therapy in people who cannot achieve adequate control of their blood sugars on insulin therapy alone. Symlin can be used for adults with either Type 1 or Type 2 diabetes. Byetta, a drug used for Type 2 diabetics, is the first in a new class of drugs called incretin mimetics; it is not a substitute for insulin. Your physician may recommend Byetta if you have not been able to control your blood sugar with oral medicines such as metformin or a sulfonylurea. It is normally administered as an injection twice a day, before breakfast and dinner, and may be given alone, or with metformin or a sulfonylurea.

Administering Insulin

Insulin is injected using a needle and syringe, cartridge, prefilled pen systems or by insulin pump. The place on the body where you inject your insulin affects the timing of its benefit to you. The abdomen has the fastest and most consistent rate of absorption, followed by the arms, thighs and buttocks. Rotation within the selected site of insulin injection is important to prevent the breakdown and scarring of fatty tissue under the skin, a condition known as lipoatrophy. By rotating within the site selected rather than among multiple sites on the body, the absorption of insulin remains relatively constant.

You should always follow your health care provider's guidelines on when to take your insulin. The time span between your insulin injection and meals will vary depending on the type of insulin you are using. For example, if you use Humalog, a rapid-acting insulin, you should generally take it 10 minutes before eating a meal or take it with your meal.

Insulin Dosage

Injectable insulin for treating diabetes is packaged in vials. The drug is available in a concentration of 100 or 500 units per milliliter (ml or cc), sometimes called U-100 or U- 500. A vial of insulin usually has 10 milliliters of the drug; so each vial contains 1,000 or 5,000 units of insulin per bottle. Most of the insulin used is U-100 concentration. An occasional patient requiring very high doses of insulin is prescribed U-500 insulin.

Your dose is calculated based on your weight and sensitivity to insulin. It can vary from 0.6u to1.2 mcg/kg.

Insulin is usually administered so that two-thirds of the total daily dose is given in the morning with one-third administered in the evening.

Side Effects of Insulin

The major side effects that can occur when taking insulin for diabetes are:

• Low blood sugar- hypoglycemia,

• Hypertrophy or enlargement of the area of the body that has received too many insulin injections,

• Injection-site rash,

• Side effects unique to inhaled insulin include cough, shortness of breath, sore throat and/or dry mouth.

Storing Insulin

You should always keep at least two bottles of your insulin on hand. The bottle that you are using may be stored at room temperature for no longer than 30 days. Store it where it will not get too hot or too cold and keep it out of direct sunlight.

Your extra bottles of insulin should be stored in the refrigerator. The night before you are ready to use your new bottle, take it out of the refrigerator and allow it to warm to room temperature. Administering cold insulin may result in more painful injections.

You should always check your insulin bottle before you use it. Rapid-acting insulin, short-acting insulin and two of the long-acting insulins, Lantus and Levemir should be clear. Other forms of insulin should have a cloudy appearance but be free of clumps.

If you are carrying your insulin with you, be careful not to shake it since this can create air bubbles that affect the amount of insulin you withdraw for an injection.

Your Insulin Prescription

When you pick up your insulin at the pharmacy, you must always check the label to make sure that it is the type prescribed by your doctor, since using the wrong type can affect your blood sugar control. You should also check the expiration date on the insulin box to insure that you will have enough time to use the entire bottle. Insulin generally loses its potency about a month after opening. To find out how long the medicine will last, divide the number of units in the bottle by the number of units you take each day. Oral Medications for Diabetes are also available, though their effectiveness and application are limited.