Insulin Regular, Injectable Solution

Prescription insulin regular (human) comes as an injectable solution, a powder for inhalation, and an intravenous injection.

Prescription insulin regular (human) injectable solution is only available as the brand-name drug Humulin R. It’s not available in a generic form. Insulin regular (human) injectable solution is also available as an over-the-counter (OTC) drug called Novolin R.

Insulin regular (human) injectable solution is short-acting and may be taken in combination with intermediate- or long-acting insulins. You inject the solution subcutaneously (under your skin).

If you have type 2 diabetes, insulin regular (human) may also be used with other classes of oral diabetes medications to help control your blood sugar.

Why it’s used

Insulin regular (human) is used along with a healthy diet and exercise to control high blood sugar in people with type 1 or type 2 diabetes.

How it works

Insulin regular (human) belongs to a class of drugs called insulins. A class of drugs refers to medications that work similarly. They have a similar chemical structure and are often used to treat similar conditions.

Insulin is a hormone that your body makes to help move sugar (glucose) from your body’s bloodstream into your cells. Your cells use the sugar as fuel for your body. If you have type 1 diabetes, your pancreas doesn’t make insulin. If you have type 2 diabetes, your body doesn’t make enough insulin, or it can’t properly use the insulin that it makes. Without enough insulin, the sugar will stay in your bloodstream, causing high blood sugar levels (hyperglycemia).

Insulin regular (human) is a short-acting, man-made insulin that’s similar to the insulin made by your pancreas. It copies your body’s insulin in response to food. This extra insulin helps to control your blood sugar and prevent complications of diabetes.

INJECTING INSULIN REGULAR (HUMAN)Your healthcare provider will show you how to give yourself the subcutaneous injection. You can also follow this guide for self-injection.

Insulin regular (human) can cause mild or serious side effects. The following list contains some of the key side effects that may occur while taking insulin regular (human). This list does not include all possible side effects.

For more information on the possible side effects of insulin regular (human), or tips on how to deal with a troubling side effect, talk with your doctor or pharmacist.

More common side effects

The more common side effects that occur with insulin regular (human) include:

• Swelling of your arms and legs
• Weight gain
• Low blood sugar (hypoglycemia). This needs to be treated. (See “Treating low blood sugar” below.) Symptoms can include:
  • sweating
  • dizziness or lightheadedness
  • shakiness
  • hunger
  • fast heart rate
  • tingling in your hands, feet, lips, or tongue
  • trouble concentrating or confusion
  • blurred vision
  • slurred speech
  • anxiety, irritability, or mood changes
• Injection site reactions. If you keep having skin reactions or they’re serious, talk to your doctor. Don’t inject insulin into skin that is red, swollen, or itchy. Symptoms at the injection site can include:
  • redness
  • swelling
  • itching
• Skin changes at the injection site (lipodystrophy). Change (rotate) the site on your skin where you inject your insulin to help reduce the chance of developing these skin changes. If you have these skin changes, don’t inject insulin into this type of skin. Symptoms can include:
  • shrinking or thickening skin at the injection sites

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious side effects

Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

• Severe low blood sugar. Symptoms include:
  • mood changes, such as irritability, impatience, anger, stubbornness, or sadness
  • confusion, including delirium
  • lightheadedness or dizziness
  • sleepiness
  • blurred or impaired vision
  • tingling or numbness in your lips or tongue
  • headaches
  • weakness or fatigue
  • lack of coordination
  • nightmares or crying out during your sleep
  • seizures
  • loss of consciousness
• Low blood potassium (hypokalemia). Symptoms include:
  • tiredness
  • weakness
  • muscle cramps
  • constipation
  • breathing problems (at a severe stage without medical attention)
  • heart rhythm problems (at a severe stage without medical attention)
• Serious allergic reaction. Symptoms include:
  • a rash all over your body
  • trouble breathing
  • fast heart rate
  • sweating
  • feeling faint
• Swelling of your hands and feet
• Heart failure. Symptoms include:
  • shortness of breath
  • swelling of your ankles or feet
  • sudden weight gain

Treating low blood sugar

If you have a low blood sugar reaction, you need to treat it.

• For mild hypoglycemia, treatment is 15 to 20 g of glucose (a type of sugar). You need to eat or drink one of the following:
  • 3 to 4 glucose tablets
  • a tube of glucose gel
  • 4 oz. of juice or regular, non-diet soda
  • 8 oz. of nonfat or 1% cow’s milk
  • 1 tablespoon of sugar, honey, or corn syrup
  • 8 to 10 pieces of hard candy, such as lifesavers
• Test your blood sugar 15 minutes after you treat the low sugar reaction. If your blood sugar is still low, then repeat the above treatment.
• Once your blood sugar is back in the normal range, eat a small snack if your next planned meal or snack is more than one hour later.

If you don’t treat low blood sugar, you can have a seizure, pass out, and possibly develop brain damage. Low blood sugar can even be fatal. If you pass out because of a low sugar reaction or cannot swallow, someone will have to give an injection of glucagon to treat the low sugar reaction. You may need to go to the emergency room.

Insulin regular (human) injectable solution can interact with several other medications. Different interactions can cause different effects. For instance, some can interfere with how well a drug works, while others can cause increased side effects.

Below is a list of medications that can interact with insulin regular (human). This list does not contain all drugs that may interact with insulin regular (human).

Before taking insulin regular (human), be sure to tell your doctor and pharmacist about all prescription, over-the-counter, and other drugs you take. Also tell them about any vitamins, herbs, and supplements you use. Sharing this information can help you avoid potential interactions.

If you have questions about drug interactions that may affect you, ask your doctor or pharmacist.

Other diabetes drugs

Taking thiazolidinediones with insulin regular (human) may cause fluid retention and heart failure. Examples of these drugs include:

• pioglitazone
• rosiglitazone

Taking pramlintide in addition to insulin regular (human) to help control your diabetes may cause very low blood sugar. If you need to take these drugs together, your doctor may adjust your dosage of insulin regular (human).

Drugs for depression

Taking certain depression drugs with insulin regular (human) may cause very low blood sugar. Examples of these drugs include:

• fluoxetine
• monoamine oxidase inhibitors (MAOIs)

Drugs for high blood pressure

Taking these blood pressure drugs with insulin regular (human) may cause very low blood sugar. Examples of these drugs include:

• enalapril
• lisinopril
• captopril
• losartan
• valsartan
• propranolol
• metoprolol

On the other hand, taking diuretics (water pills) with insulin regular (human) may cause high blood sugar.

Drug for heart rate disorders

Taking disopyramide with insulin regular (human) may cause very low blood sugar.

Drugs to treat cholesterol

Taking certain cholesterol drugs with insulin regular (human) may cause high blood sugar levels. Examples of these drugs include:

• niacin

Drugs for pain

Taking salicylates, such as aspirin, with insulin regular (human) may cause very low blood sugar.

Drug in the drug class somatostatin analogs

Taking octreotide with insulin regular (human) may cause very low blood sugar (hypoglycemia).

Drug that thins the blood

Taking pentoxifylline with insulin regular (human) may cause very low blood sugar.

Drugs for allergy or asthma

Taking these drugs with insulin regular (human) may cause high blood sugar levels. Examples of these drugs include:

• corticosteroids
• sympathomimetic agents

Hormones used in birth control

Taking these drugs with insulin regular (human) may cause high blood sugar levels. Examples of these drugs include:

• estrogens
• progesterone

Drugs used to treat HIV

Taking protease inhibitors with insulin regular (human) may cause high blood sugar levels. Examples of these drugs include:

• ritonavir
• saquinavir

Drugs for psychiatric disorders

Taking these drugs with insulin regular (human) may cause high blood sugar levels. Examples of these drugs include:

• olanzapine
• clozapine
• phenothiazines

Drug for tuberculosis

Taking this drug with insulin regular (human) may cause high blood sugar levels. Examples of these drugs include:

• isoniazid

Certain antibiotic drugs

Taking these drugs with insulin regular (human) may cause high or low blood sugar levels. Examples of these drugs include:

• sulfonamide antibiotics
• pentamidine

Drugs for hormone disorders

Taking these drugs with insulin regular (human) may cause high blood sugar levels. Examples of these drugs include:

• danazol
• glucagon
• somatropin
• thyroid hormones

Drugs for heart disorders

Taking these drugs with insulin regular (human) may mask the signs of low blood sugar. Examples of these drugs include:

• beta-blockers, such as propranolol, labetalol, and metoprolol
• clonidine
• guanethidine
• reserpine

The insulin regular (human) dosage your doctor prescribes will depend on several factors. These include:

• the type and severity of the condition you’re using insulin regular (human) to treat
• your age
• the form of insulin regular (human) you take
• other medical conditions you may have

Typically, your doctor will start you on a low dosage and adjust it over time to reach the dosage that’s right for you. They’ll ultimately prescribe the smallest dosage that provides the desired effect.

The following information describes dosages that are commonly used or recommended. However, be sure to take the dosage your doctor prescribes for you. Your doctor will determine the best dosage to suit your needs.

Drug forms and strengths

Brand: Humulin R

• Form: injectable solution, 3 mL and 10 mL vials
• Strength: 100 units/mL

• Form: injectable solution, 20 mL vial
• Strength: 500 units/mL

• Form: injectable solution, 3 mL KwikPen
• Strength: 500 units/mL

Dosage for type 1 diabetes

Adult dosage (ages 18–64 years)

• Insulin regular (human) is usually given three or more times per day before meals.
• You should eat your meal within 30 minutes after giving an injection.
• Average insulin requirements range between 0.5 and 1 unit/kg per day.
• If you’re just starting insulin therapy, your dosage may be lower, between 0.2 and 0.4 unit/kg per day.
• You’ll inject insulin regular (human) under your skin in the fatty part of your abdomen, thigh, buttocks, or back of your arm. This is where insulin is absorbed fastest.

Child dosage (ages 0–17 years)

• The total daily insulin requirements for children are usually between 0.5 and 1 unit/kg per day.
• Children who haven’t gone through puberty yet may need more insulin. Dosages may be between 0.7 and 1 unit/kg per day.

Senior dosage (ages 65 years and older)

Your body may process this drug more slowly. Your doctor may start you on a lower dosage so that too much of this drug doesn’t build up in your body. Too much of the drug in your body can be dangerous.

Dosage for type 2 diabetes

Adult dosage (ages 18–64 years)

• Insulin regular (human) is usually given three or more times per day before meals.
• You should eat your meal within 30 minutes after giving an injection.
• Average insulin requirements range between 0.5 and 1 unit/kg per day.
• If you’re just starting insulin therapy, your dosage may be lower, between 0.2 and 0.4 unit/kg per day.
• You’ll inject insulin regular (human) under your skin in the fatty part of your abdomen, thigh, buttocks, or back of your arm. This is where insulin is absorbed fastest.

Child dosage (ages 0–17 years)

• The total daily insulin requirements for children are usually between 0.5 and 1 unit/kg per day.
• Children who haven’t gone through puberty yet may need more insulin. Doses may be between 0.7 and 1 unit/kg per day.

Senior dosage (ages 65 years and older)

Your body may process this drug more slowly. Your doctor may start you on a lower dosage so that too much of this drug doesn’t build up in your body. Too much of the drug in your body can be dangerous.

Special dosage considerations

• For people with kidney disease: Insulin is generally removed from your body by your kidneys. If your kidneys aren’t working as well, insulin may build up in your body and cause low blood sugar. Your doctor may start you at a lower dosage and slowly increase it if needed.
• For people with liver disease: If you have liver disease, this drug may build up in your body. Your doctor may start you at a lower dosage and slowly increase it if needed. You and your doctor should monitor your blood sugar very closely.

This drug comes with several warnings.

Low blood sugar warning

Insulin regular (human) can cause low blood sugar (hypoglycemia). If you have a low blood sugar reaction, you’ll need to treat it right away. Symptoms can include:

• hunger
• dizziness
• shakiness
• lightheadedness
• sweating
• irritability
• headache
• fast heart rate
• confusion

Thiazolidinedione warning

Taking certain diabetes pills called thiazolidinediones (TZDs) with insulin regular (human) may cause heart failure in some people. This can happen even if you’ve never had heart failure or heart problems before. If you already have heart failure, it may get worse. Your healthcare provider should monitor you closely while you’re taking TZDs with insulin regular (human).

Tell your doctor right away if you have new or worse symptoms of heart failure, including:

• shortness of breath
• swelling of your ankles or feet
• sudden weight gain

Infection warning

Do not share insulin vials, syringes, or prefilled pens with other people. Sharing or reusing needles or syringes with another person puts you and others at risk for various infections.

Allergy warning

Insulin regular (human) can cause a severe, whole-body allergic reaction. Symptoms can include:

• skin rash and hives
• itching
• trouble breathing
• tightness in your chest
• fast heart rate
• swelling of your face, lips, tongue, or throat
• sweating

If you develop these symptoms, call 911 or go to the nearest emergency room.

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal (cause death).

Food interactions warning

Increasing how many carbohydrates (sugars) you eat can raise your blood sugar. Your insulin regular (human) dosage may need to be increased if your blood sugar can’t be controlled on your current insulin regular (human) dosage.

Decreasing the amount of carbohydrates you eat can lower your blood sugar. Your insulin regular (human) dosage may need to be decreased to make sure you don’t have a low blood sugar reaction.

You shouldn’t skip meals when you take insulin regular (human). If you’ve injected a dose, you must eat to prevent a low blood sugar reaction.

Alcohol interaction warning

Limit your alcohol intake because it can affect your blood sugar.

If you drink alcohol while using insulin regular (human), your blood sugar levels may become too low. Alcohol can also be high in calories, especially when consumed in large amounts. These additional calories may increase your blood sugar levels.

Warnings for people with certain health conditions

For people with kidney disease: Insulin is removed from your body by your kidneys. If your kidneys aren’t working well, insulin may build up in your body and cause low blood sugar. Your doctor may start you at a lower dose and slowly increase your dose if needed.

For people with liver disease: If you have liver failure, this drug may build up in your body. Your doctor may start you at a lower dosage and slowly increase your dosage if needed if you have liver problems. You and your doctor should monitor your blood sugar very closely.

For people with heart failure: Taking certain diabetes medications called thiazolidinediones (TZDs) with insulin regular (human) may make your heart failure worse. Your healthcare provider should watch you closely while you’re taking TZDs with insulin regular (human). Tell your doctor if you have any new or worse symptoms of heart failure.

For people with low blood potassium (hypokalemia): Insulin can cause a shift in potassium levels, which can lead to low blood potassium. If you’re using potassium-lowering medications with insulin regular (human), your doctor will check your blood sugar and potassium often.

Warnings for other groups

For pregnant women: Studies have not shown any risk to the fetus if the mother uses insulin regular (human). Still, this drug should be used during pregnancy only if the potential benefit justifies the potential risk.

Tell your doctor if you’re pregnant or plan to become pregnant. Pregnancy may make managing your diabetes more difficult. Good control of diabetes is important for you and your fetus, so be sure to work with your doctor to manage your condition during pregnancy.

For women who are breastfeeding: Insulin may pass into breast milk and get broken down by the child’s stomach. Insulin doesn’t cause side effects in children who are breastfed by mothers with diabetes. However, if you breastfeed, the amount of insulin you need may change. Your doctor may change your dosage while you breastfeed.

For children: Children with type 1 diabetes may be more likely to have low blood sugar than adults with type 1 diabetes. Your child should be monitored closely on this medication.

Insulin regular (human) injectable solution is used for long-term treatment. It comes with serious risks if you don’t take it as prescribed.

If you don’t take it at all: If you don’t take insulin regular (human) at all, you may still have high blood sugar levels and the symptoms associated with it. Over time, high blood sugar levels can harm your eyes, kidneys, nerves, or heart. Severe issues include heart attack, stroke, blindness, kidney failure and dialysis, and possible amputations.

If you don’t take it on schedule: If you don’t inject insulin regular (human) on schedule, your blood sugar levels may not be well controlled. If your injections are given too close together, you may have low blood sugar. If your injections are given too far apart, you may have high blood sugar.

If you take too much: Insulin regular (human) comes with serious risks if you don’t take it as prescribed. For instance, Humulin U-500 insulin is five times more concentrated than regular insulin (sometimes called U-100 insulin). If you use the wrong product or measure out your dose incorrectly, you can overdose on insulin.

Always double-check that you’re using the type of insulin that your doctor prescribed. Ask your doctor or pharmacist to show you how to measure it out so you get the right dose.

If you inject too much insulin regular (human), you may experience low blood sugar. See “Side effects” (above) for symptoms. Mild episodes of low blood sugar can usually be treated by drinking a glass of cow’s milk or half a glass of regular soda or juice, or by eating five to six hard candies. If it’s more severe, it can lead to coma or seizure. Low blood sugar may even be fatal.

If you’ve taken too much insulin regular (human), call 911 or go to the emergency room right away.

If you inject too much insulin regular (human), you may also experience low blood potassium (hypokalemia). This condition usually doesn’t cause symptoms. If symptoms do occur, they can include tiredness, weakness, and constipation. You should tell your doctor if you took too much insulin so that they can check your blood potassium level and treat it if needed.

What to do if you miss a dose: You should inject insulin regular (human) 30 minutes before a meal. If you forget to take your dose and you just finished your meal, go ahead and inject your dose.

If a long time has passed since you’ve eaten your meal, call your doctor for instructions on what to do.

Never try to catch up by doubling the amount of insulin regular (human) you should inject. This could cause low blood sugar.

How to tell if the drug is working: Your blood sugar should be lower. Your doctor will do tests to check what your average blood sugar has been over the past two to three months (A1C).

Your symptoms of high blood sugar, such as feeling very hungry or thirsty or urinating often, should decrease.

Keep these considerations in mind if your doctor prescribes insulin regular (human) for you.

General

• You should eat a meal within 30 minutes of injecting insulin regular (human).
• Take this drug at the time(s) recommended by your doctor.

Storage

• Humulin R U-100
  • Not in use (unopened):
    • Store it in the refrigerator from 36°F to 46°F (2°C to 8°C).
    • Don’t freeze the medication.
  • In use (opened):
    • Store it below 86°F (30°C). It doesn’t have to be refrigerated.
    • Keep it away from heat and light.
    • In-use vials must be used within 31 days. After 31 days, throw away the vial, even if there’s insulin left in it.
    • Don’t use Humulin after the expiration date on the label or after it’s been frozen.
• Humulin R U-500
  • Not in use (unopened):
    • Store it in the refrigerator at a temperature between 36°F and 46°F (2°C and 8°C).
    • Don’t freeze the medication.
  • In use (opened)
    • Store it at room temperature below 86°F (30°C). It doesn’t have to be refrigerated.
    • Pens must be kept at room temperature.
    • Keep it away from heat and light.
    • In-use vials must be used within 40 days. After 40 days, throw away the vial, even if there’s insulin left.
    • In-use pens must be used within 28 days. After 28 days, throw away the pen, even if there’s insulin left.
    • Don’t use Humulin R U-500 after the expiration date on the label or after it’s been frozen.

Refills

A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

• Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
• Don’t worry about airport X-ray machines. They can’t harm your medication.
• You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled container with you.
• This medication needs to be refrigerated for vials not currently in use. You may need to use an insulated bag with a cold pack to maintain the temperature when traveling.
• Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.
• Needles and syringes need to be used to take this medication. Check for special rules about traveling with needles and syringes.
• Let your doctor know if you’re traveling across more than two time zones. They may need to adjust your insulin schedule.

Self-management

While taking this drug, you’ll also need to learn how to recognize the signs of high and low blood sugar, and be able to manage these conditions when needed. Your doctor, nurse, pharmacist, or diabetes educator will show you how to:

• use a blood glucose monitor to test your blood sugar levels
• prepare and inject your insulin regular (human) using syringes and vials
• withdraw insulin from the vial, attach needles, and give the insulin regular (human) injection

While using insulin regular (human), you’ll need to purchase the following:

• blood glucose monitor
• sterile alcohol wipes
• lancing device and lancets (a needle used to obtain drops of blood from your finger to test your blood sugar)
• syringes and needles
• blood glucose test strips
• needle container for safe disposal of lancets, needles, and syringes

When injecting:

• Inject insulin regular (human) into the fatty part of your skin (subcutaneous fat). The best places include your stomach, buttocks, upper legs (thighs), or the outer part of your upper arm.
• Be sure to change (rotate) the site of injection each time.
• Don’t inject yourself where you have irritated or red skin.
• You should never share your insulin vials, syringes, or prefilled pens with anyone else. Sharing these items puts you and others at risk of infection.
• If you have vision problems and use the Humulin R U-500 KwikPen, you may depend on hearing the “clicks” to dial your correct dose. If so, you may need to have someone who can see well check your dose before you inject the medication.

Clinical monitoring

Your doctor may do certain tests before you begin and regularly during treatment with insulin to make sure it’s safe for you to take. They may need to adjust your dosage of insulin regular (human) based on following:

• blood sugar level
• glycosylated hemoglobin (A1C) levels. This test measures your blood sugar control over the last two to three months.
• liver function
• kidney function
• other medications that you’re taking
• exercise habits
• carbohydrate content of meals

Your doctor may do other tests to check for complications of diabetes. These may include:

• eye exam at least once a year
• foot exam at least once a year
• dental exam at least once a year
• tests for nerve damage
• cholesterol test
• blood pressure and heart rate

Your diet

Making healthy food choices and tracking your eating habits can help you manage your diabetes. Follow the nutrition plan that your doctor, registered dietitian, or diabetes educator recommended.

Hidden costs

Besides the medication, you’ll need to purchase the following:

• sterile alcohol wipes
• lancing device and lancets (a needle used to obtain drops of blood from your finger to test your blood sugar)
• syringes and needles
• blood glucose test strips
• blood glucose monitor
• needle container for safe disposal of lancets, needles, and syringes

Prior authorization

Many insurance companies require a prior authorization for this drug. This means your doctor will need to get approval from your insurance company before your insurance company will pay for the prescription.

There are other drugs available to treat your condition. Some may be better suited for you than others. Talk to your doctor about other drug options that may work for you.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.