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Insulin (Regular, Rapid-acting, or Semilente)

Brand Names: Humulin BR, Humulin R, Novolin R, Novolin R Pen-Fill Cartridges, Regular Iletin I (beef and pork), Regular Iletin II (purified beef), Regular Iletin II (purified pork), Semilente Iletin I (beef and pork), Semilente Insulin (beef), Velosulin Human, Velosulin (purified pork)
Drug Class: Antidiabetic agent
Available in: Injection
Available OTC? Yes
As Generic? No

Side Effects

Serious: Symptoms of hypoglycemia can be caused by the release of adrenaline or by an inadequate supply of glucose to the brain. With severe hypoglycemia, lack of sufficient glucose to the brain may cause slurred speech, impaired concentration, confusion, seizures, coma, irreversible brain damage, and death. Mild hypoglycemia may cause restless sleep, nightmares, or a cold sweat that awakens patients at night.

Common: Symptoms resulting from release of adrenaline are common manifestations of mild to moderate hypoglycemia. They include cold sweats, anxiety, shakiness, hunger, rapid heartbeat, headache, and nervousness. Weight gain is common when taking insulin.

Less Common: Allergic reactions, lipoatrophy (depressions in the skin due to loss of fat tissue), and lipohypertrophy (excessive accumulation of fat tissue).

Principal Uses

For long-term treatment of diabetes mellitus. All patients with type 1 diabetes require lifelong insulin treatment. Patients with type 2 diabetes may require insulin if they are unable to control their blood glucose (sugar) levels with diet and oral medications.

How the Drug Works

Insulin, a hormone secreted by the beta cells of the pancreas, plays an essential role in controlling the metabolism and storage of carbohydrates, fat, and protein. Insulin is secreted in response to a rise in blood sugar (glucose). Insulin lowers blood glucose by increasing its uptake by body cells, especially muscle, and by reducing the release of glucose from the liver between meals.


It may be taken 1 to 4 times daily, before meals and possibly at bedtime. Doses and frequency are determined by your doctor. Regular (or rapid-acting or semilente) insulin should be administered 30 to 45 minutes before a meal. It can be mixed in the same syringe with intermediate-acting insulins. Draw up the regular insulin first.

Onset of Effect

Within 45 minutes; peak effect occurs within 2 to 4 hours.

Duration of Action

From 4 to 6 hours.

Dietary Advice

All patients with diabetes should follow the general dietary recommendations of the American Diabetes Association. Though intake of simple sugars is not forbidden, consuming a large amount of sugary foods at one time may trigger a rapid rise in blood glucose that can increase urination and thirst. In addition, patients who take insulin must remain consistent from day to day in the timing and caloric content of their meals. Depending on the timing, dose, and types of insulin prescribed, snacks may be recommended in the late afternoon, before bedtime, or prior to unusual physical activity. Diabetic patients must always have available juice, food, or tablets that can raise blood glucose levels rapidly to counter an episode of hypoglycemia.


Refrigerate insulin but do not allow it to freeze. Insulin does not have to be kept refrigerated when you are traveling for short periods, but exposure to high temperatures must be avoided.

If You Miss a Dose

Timing of insulin doses is extremely important. The best approach is to measure blood glucose and add a dose of regular insulin if glucose levels are too high. Otherwise, wait for the next scheduled dose.

Stopping the Drug

Do not stop taking insulin injections unless ordered by your doctor. Patients with diabetes are often given general instructions for modifying their insulin doses based on home blood glucose measurements.

Prolonged Use

After many years with diabetes, some patients become insensitive to the symptoms of hypoglycemia and are at risk for serious brain complications of prolonged, unrecognized hypoglycemia.


Over 60: No special warnings. Some older people may, however, have vision problems that may make it difficult to draw up the correct dose of insulin.

Driving and Hazardous Work: Patients taking insulin must be very careful to avoid hypoglycemia when driving or engaging in hazardous work.

Alcohol: Moderate alcohol intake, especially when taken with large meals, does not adversely affect control of diabetes or alter the dose of insulin. However, large amounts of alcohol increase the risk of hypoglycemia.

Pregnancy: Strict metabolic control, using insulin injections in most women, must be maintained during pregnancy to reduce the risk of birth defects, fetal complications, or death at the time of delivery. In women who had diabetes before the onset of pregnancy, the dose of insulin is often smaller during the first third (trimester) of pregnancy and then higher during the final two trimesters. When women first develop diabetes during pregnancy (gestational diabetes), insulin requirements drop rapidly after delivery and most do not need to continue with insulin treatment.

Breast Feeding: Insulin requirements tend to be lower during breast feeding. Home glucose monitoring is important to avoid hypoglycemia. Insulin is not present in breast milk.

Infants and Children: Treatment with insulin in young patients is the same as that in older people with diabetes.

Special Concerns: Inadequate amounts of insulin in type 1 diabetes may lead to the serious complication of diabetic ketoacidosis, characterized by loss of appetite, excessive thirst and urination, nausea, vomiting, deep breathing, fruity breath odor, drowsiness, confusion, and loss of consciousness.


Symptoms: Insulin overdose results in hypoglycemia (see Side Effects for symptoms).

What to Do: For mild to moderate hypoglycemia, ingest drinks or food containing sugar. For more severe hypoglycemia, administer injections of glucagon or call emergency medical services (EMS) immediately.

Drug Interactions

A large number of drugs can promote either elevated blood glucose levels or hypoglycemia. Be sure that your doctor knows about all of the medications you take and is informed before you start taking any new drugs, either by prescription or over the counter. Corticosteroids in particular are likely to raise blood glucose levels and insulin requirements. Beta-blockers (commonly prescribed for hypertension) may cause either high blood glucose levels or hypoglycemia; in addition, because these medications may dampen the symptoms of hypoglycemia that are caused by adrenaline release, mild degrees of hypoglycemia may progress unnoticed to more serious hypoglycemia affecting the brain.

Food Interactions

Insulin requirements are increased when larger amounts of calories are ingested, especially simple sugars and carbohydrates.

Disease Interactions

Insulin requirements are increased by infections, psychological stress, or an uncontrolled overactive thyroid, and often at the time of surgery. Requirements may diminish with kidney disease or an underactive adrenal or pituitary gland.


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