Insulin information

Definition
Insulin is a hormone produced by the pancreas to regulate levels of blood glucose (a blood sugar that supplies the body with energy). As a prescription medication, insulin is taken by people who have diabetes, a condition in which glucose cannot work properly because of a lack of insulin or a problem with insulin metabolism.

How it works
Insulin reduces blood sugar by helping the body store carbohydrates as glycogen in the liver and muscle tissue. Then, the glycogen is converted to glucose and released to the body on demand. Insulin also stops the breakdown of protein.
Insulin works like a key to open the cells in your body to accept glucose from the bloodstream. This provides you with energy. If your pancreas has stopped producing insulin or is not making enough insulin, you must begin insulin injections.

Insulin can be short-acting, intermediate-acting or long-acting. Common terms used to describe insulin include onset, peak and duration. Onset is the time it takes for insulin to reach the bloodstream. Peak is the period of time the insulin is working hardest to lower your blood sugar. Duration is the length of time the insulin will be working in your bloodstream.

Common types of insulin Type Onset Peak Duration
Rapid-acting Lispro (Humalog), Aspart (NovoLog) 5 to 15 minutes 45 to 90 minutes 3 to 4 hours
Fast-acting (Regular) 30 minutes 2 to 5 hours 5 to 8 hours
Intermediate-acting (NPH or Lente) 1 to 3 hours 6 to 12 hours 16 to 24 hours
Long-acting Ultralente 4 to 6 hours 8 to 20 hours 24 to 28 hours
Long-acting Glargine (Lantus) 1 hour peakless 24 hours



Premixed insulins, with intermediate-acting insulin mixed with either fast- or rapid-acting insulin in one bottle, are also available. This is helpful for people who have poor eyesight or dexterity, which makes drawing out of two bottles more difficult. Some mixes are available in a prefilled insulin pen, making it even easier and more accurate to administer the insulin. Each component has variable peaks and durations.

Sources of insulin
Through genetic engineering, bacteria or yeast cells can be altered to produce human insulin, which is used almost exclusively in the United States. The onset, peak and duration times can be manipulated by adding zinc, acetate buffers and protamine (a simple protein) in different ways.
Rapid-acting insulins are synthetic insulin analogs that have a faster onset and shorter duration than regular human insulin. They are taken along with a longer-acting insulin to mimic the normal rapid secretion of insulin that occurs after eating in someone who does not have diabetes.

A new insulin called glargine (Lantus) is a true basal insulin that lasts 24 hours and has no peak. When glargine is used along with three injections of rapid-acting insulin at meals, the normal human pattern of insulin secretion is mimicked.


When it is used
To keep blood sugar levels as close to normal as possible, some people who have diabetes need daily injections of insulin. Insulin schedules and dosages are based on your unique needs. You'll work closely with your doctor to determine the insulin regimen that's right for you.

Methods of administration
Insulin can be given in a variety of ways.
You can use a syringe to give yourself a traditional shot of insulin.

With an insulin pump, insulin is delivered through a narrow tube connected to a needle, which is placed underneath the skin on your abdomen. The pump weighs 4 to 6 ounces, is about the size of a beeper, and can be attached to a belt or placed in your pocket. Refillable cartridges contain enough insulin for about two days. The pump can provide a continuous flow of insulin or several units at once, either before meals or when your blood sugar level is too high.

An insulin pen is a device resembling an ink pen. It contains a cartridge filled with 100 to 200 units of insulin. The device features a thin replaceable needle at the end of the pen, as well as a dial that allows you to inject the desired amount of insulin just under the skin when you push a special plunger.

An insulin jet injector also resembles an ink pen. This device sprays a fine mist of insulin through the skin with the help of a high air pressure mechanism. Cost is often a drawback to jet injectors.

Insulin patches, implantable insulin pumps, inhaled insulin, oral insulin and other insulin analogues may soon be available as other options.

Patient education
For insulin to work properly, it must be balanced with the amount, type and frequency of foods you eat, along with your activity level. Keep the following suggestions in mind:
Wash your hands with soap and water before preparing the medication. Insulins that separate, such as NPH, need to be rolled between your hands -- do not shake them. Also, verify that the medication is the correct form of insulin and has not expired. Any change in the insulin bottle (such as clumping, frosting on the glass or a layer in the bottom of the vial) may be a sign of decreased potency. If you opt for an insulin pump, follow the manufacturer's instructions.

Insulin should be taken at the same time each day (unless you're following a glargine/Humalog schedule). Follow your doctor's instructions for proper timing around meals. Your doctor will help you determine the appropriate frequency and dosage, depending on the results of blood glucose monitoring. Continue taking insulin even when you're sick, though your doctor may adjust the dosage. Do not stop taking insulin without your doctor's close supervision. Dosages may also need to be adjusted if you change your diet or activity level. Of course, discuss any changes with your doctor.

Rotate the injection sites on a regular basis. When running, swimming, or doing aerobics or any other exercise involving your arms or legs, inject the insulin into your abdominal area. Because of the increased blood flow, the body typically absorbs insulin faster from an extremity after vigorous exercise.

When mixing short-acting with a longer-acting insulin, always draw up the clear (short-acting) insulin first (except glargine, which cannot be mixed with any other insulin).

Follow the manufacturer's storage instructions. Generally, insulin can be kept at room temperature for one month. Throw away the bottle after one month. If it takes longer than one month to use the entire bottle, you may store it in the refrigerator until the expiration date printed on the label.

Insulin cannot be exposed to extreme temperatures. It breaks down and does not work properly if it gets too hot or cold. Don't store insulin in the freezer, don't leave it sitting on the counter in the sun, and don't store it in your vehicle's glove compartment.

Because injection needles have a silicone coating, do not wipe them with alcohol -- alcohol can remove the coating, which can make injections painful.

To avoid injury, handle syringes and needles carefully. The disposable variety are designed for single use and should be discarded in a puncture-proof container. Check with your local health department for more information on disposal regulations in your area.

Make sure anyone giving insulin or providing care to a child who has diabetes understands proper technique and timing, as well as the symptoms of a diabetic emergency. Children are especially sensitive to the effects of insulin before puberty, making hypoglycemia common. After puberty, the amount of insulin needed may decrease.

Insulin and travel
When you travel, pack enough insulin and related supplies to last throughout your trip. Try to avoid major changes in your eating habits, and carry snacks with you at all times. Store your insulin in an insulated container if it may be exposed to temperature extremes, such as in the luggage compartment of an airplane. Or, better yet, carry it with you on the plane. The security X-ray machines will not affect insulin or glucose meters.
The Transportation Security Administration, established to enforce airport security measures, offers the following recommendations for passengers who have diabetes:

Notify the security screener you have diabetes and are carrying your supplies.

Bring a professionally printed pharmaceutical label identifying your insulin. This type of label is usually found on the insulin box.

You can carry as many syringes as you want, but you must have the insulin with you to get the syringes through security.

Lancets, blood glucose meters and test strips can be carried through security. Lancets must be carried with a glucose meter containing the manufacturer's name embossed on the meter.

If you're wearing an insulin pump, request the screeners visually inspect the pump rather than removing it from your body.

Drug interactions
In addition to cigarettes and alcohol, certain drugs may alter blood glucose levels or interact with insulin, including:
beta blockers
corticosteroids
pentamidine
oral contraceptives
MAO inhibitors
diltiazem
clofibrate
guanethidine
phenylbutazone
thiazide diuretics
thyroid hormones
salicylates
tetracycline
sulfinpyrazone
marijuana
Discuss the use of over-the-counter medications for appetite control, asthma, or cold, cough, allergy or sinus symptoms with your doctor.


Adverse reactions
If you develop hypoglycemia, eat something high in carbohydrate sugar, such as fruit juice, honey, nondiet soda, crackers or a sandwich. Avoid chocolate -- its fat content slows the sugar from entering your bloodstream. Then, to prevent further hypoglycemia, eat a snack high in protein. Keep glucagon (a medication that increases blood glucose) readily available. It must be given by injection. In case you're unable to give yourself glucagon, make sure a family member or friend understands how to use it, and always check the expiration date.
Other adverse reactions may include:

rebound hyperglycemia (high blood sugar following hypoglycemia due to the release of hormones)
allergic reactions ranging from a rash to potentially life-threatening anaphylaxis
irritation at the injection site, such as discomfort, redness, swelling, warmth or lumps
injury to fat tissue at the injection site
Notify your doctor if you have persistent problems at an injection site. Seek immediate medical attention if you faint or develop hives, a rash or intense itching soon after a dose of insulin.


Considerations
If you have diabetes, carry a medical ID card or wear an ID bracelet. If you're resistant to insulin (due to an insulin allergy, for example) make sure you seek additional medical evaluation.

Pregnancy-specific information
During pregnancy, carefully controlling your blood glucose level increases your odds of delivering a healthy baby. If this cannot be done appropriately through diet alone, your doctor will prescribe insulin. It may be easier to maintain your blood glucose levels through multiple insulin injections or a pump that continuously delivers small doses of insulin. (Oral hypoglycemic medications are not safe during pregnancy.)
If your blood glucose level is optimally controlled over a period of five to six weeks, your glycosylated hemoglobin (Hb A1c) levels will be normal. This blood test is an indicator of your average blood glucose level. It should be normal during pregnancy to avoid complications, fetal anomalies or miscarriage. The goal is a result less than 7 percent, with 4 to 6 percent considered optimal. Your doctor will discuss a change in your treatment plan if the result is higher than 8 percent. If your glycosylated hemoglobin is greater than 10, labor may be induced early to prevent post-term delivery and a larger infant, as well as minimize complications such as hydramnios (excessive amniotic fluid, the fluid that surrounds and protects the fetus in the womb, which leads to a stretched-out uterus and the potential for the fetus to be in an abnormal position).


Senior-specific information
After age 60, recurrent episodes of hypoglycemia are associated with confusion and abnormal behavior. As you age, it's especially important to maintain optimal control of your blood sugar levels. If you have vision problems or other difficulties, ask your doctor about special medical equipment (such as prisms and magnifiers) to help you read the numbers on the syringe. Voice glucose monitors are also available.