Insulin is a hormone that works by lowering levels of glucose (sugar) in the blood. Concentrated (U-500) insulin is a long-acting insulin that starts to work several hours after injection and keeps working evenly for 24 hours. U-500 insulin is five times more concentrated than regular U-100 insulin.

U-500 insulin is used to improve blood sugar control in adults and children with diabetes mellitus who have significant daily insulin needs (more than 200 units per day).

U-500 insulin may also be used for purposes not listed in this medication guide.

Never share an injection pen, cartridge, or syringe with another person, even if the needle has been changed.

U-500 insulin is concentrated and contains 500 units of insulin in each milliliter (mL). This is five times more concentrated than regular U-100 insulin, which contains 100 units per mL. Measure each dose of U-500 insulin carefully. Using too much insulin can lead to insulin shock or death. Follow all directions on your prescription label. Do not use this medicine in larger or smaller amounts or for longer than recommended.

Insulin is injected under the skin. A healthcare provider can teach you how to properly use the medication by yourself.

U-500 insulin must not be given with an insulin pump, or mixed with other insulins. Do not inject U-500 insulin into a vein or a muscle.

Read and carefully follow any Instructions for Use provided with your medicine. Ask your doctor or pharmacist if you don't understand all instructions.

Prepare an injection only when you are ready to give it. Do not use if the medicine looks cloudy, has changed colors, or has particles in it. Call your pharmacist for new medicine.

Your healthcare provider will show you where on your body to inject U-500 insulin. Use a different place each time you give an injection. Do not inject into the same place two times in a row.

Do not inject this medicine into skin that is damaged, tender, bruised, pitted, thickened, scaly, or has a scar or hard lump.

After using U-500 insulin, you should eat a meal within 30 minutes.

If you use an injection pen, use only the injection pen that comes with U-500 insulin. Attach a new needle before each use. Do not transfer the insulin from the pen into a syringe. The injection pen has a dial on it that allows you to set your correct doses of U-500 insulin.

If you use U-500 insulin from a vial (bottle), use only a U-500 insulin syringe to inject the medicine. Do not use any other type of syringe.

Do not convert your dose when using a U-500 injection pen or U-500 insulin syringe.

Never share an injection pen, cartridge, or syringe with another person, even if the needle has been changed. Sharing these devices can allow infections or disease to pass from one person to another.

Use a needle and syringe only once and then place them in a puncture-proof "sharps" container. Follow state or local laws about how to dispose of this container. Keep it out of the reach of children and pets.

You may have low blood sugar (hypoglycemia) and feel very hungry, dizzy, irritable, confused, anxious, or shaky. To quickly treat hypoglycemia, eat or drink a fast-acting source of sugar (fruit juice, hard candy, crackers, raisins, or non-diet soda).

Your doctor may prescribe a glucagon injection kit in case you have severe hypoglycemia. Be sure your family or close friends know how to give you this injection in an emergency.

Also watch for signs of high blood sugar (hyperglycemia) such as increased thirst or urination.

Blood sugar levels can be affected by stress, illness, surgery, exercise, alcohol use, or skipping meals. Ask your doctor before changing your dose or medication schedule.

U-500 insulin is only part of a complete treatment program that may also include diet, exercise, weight control, blood sugar testing, and special medical care. Follow your doctor's instructions very closely.

Keep this medicine in its original container protected from heat and light. Do not draw insulin from a vial into a syringe until you are ready to give an injection. Do not freeze insulin or store it near the cooling element in a refrigerator. Throw away any insulin that has been frozen.

Storing unopened (not in use) U-500 insulin:

• Refrigerate and use until expiration date; or

• Store at room temperature and use within 28 days.

Storing opened (in use) U-500 insulin:

• Store the vial in a refrigerator or at room temperature and use within 40 days. Do not shake the vial.

• Store the injection pen at room temperature (do not refrigerate) and use within 28 days. Do not store the injection pen with a needle attached.

In case of emergency, wear or carry medical identification to let others know you have diabetes.

You should not use Humulin R (Concentrated) if you are allergic to insulin, or if you are having an episode of hypoglycemia (low blood sugar).

Tell your doctor if you have ever had:

• liver or kidney disease; or

• low levels of potassium in your blood (hypokalemia).

Tell your doctor if you also take pioglitazone or rosiglitazone (sometimes contained in combinations with glimepiride or metformin). Taking certain oral diabetes medicines while you are using insulin may increase your risk of serious heart problems.

Tell your doctor if you are pregnant or breastfeeding.

Follow your doctor's instructions about using insulin if you are pregnant or you become pregnant. Controlling diabetes is very important during pregnancy, and having high blood sugar may cause complications in both the mother and the baby.

Follow your doctor's directions if you miss a dose. To prevent missed doses, keep insulin on hand at all times. Get your prescription refilled before you run out of medicine completely.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. Insulin overdose can cause life-threatening hypoglycemia. Symptoms include drowsiness, confusion, blurred vision, numbness or tingling in your mouth, trouble speaking, muscle weakness, clumsy or jerky movements, seizure (convulsions), or loss of consciousness.

Avoid medication errors by always checking the medicine label before injecting your insulin.

Avoid drinking alcohol. It can cause low blood sugar and may interfere with your diabetes treatment.

Get emergency medical help if you have signs of insulin allergy: redness or swelling where an injection was given, itchy skin rash over the entire body, trouble breathing, fast heartbeats, feeling like you might pass out, or swelling in your tongue or throat.

Humulin R (Concentrated) may cause serious side effects. Call your doctor at once if you have:

• fluid retention--weight gain, swelling in your hands or feet, feeling short of breath; or

• low potassium--leg cramps, constipation, irregular heartbeats, fluttering in your chest, increased thirst or urination, numbness or tingling, muscle weakness or limp feeling.

Common side effects of Humulin R (Concentrated) may include:

• low blood sugar;

• itching, mild skin rash; or

• thickening or hollowing of the skin where you injected the medicine.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Many other medicines can affect your blood sugar, and some medicines can increase or decrease the effects of insulin. Some drugs can also cause you to have fewer symptoms of hypoglycemia, making it harder to tell when your blood sugar is low. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using. This includes prescription and over-the-counter medicines, vitamins, and herbal products.