Humulin R (Insulin Human Regular) - Injection

What Is Humulin R?

Humulin R is a prescription drug used to lower blood sugar in people with high blood sugar (diabetes). It’s a short-acting insulin drug available as a solution for injection or infusion.

Humulin R works by allowing blood sugar (glucose) to enter your cells and be used for energy by your body. This lowers your blood sugar. 

Humulin R is usually used in combination with intermediate- or long-acting insulin or given through a continuous insulin infusion pump under the skin. A blood test, the hemoglobin A1C (HbA1c) test, is used to measure how well this drug is working for you. It measures your average blood sugar levels over the last three months. The goal is to get to an HbA1c of less than 7% as quickly as possible by safely adjusting your dosage.

Drug Facts

Generic Name: Insulin Human Regular

Brand Name(s): Humulin R

Drug Availability: Prescription

Therapeutic Classification:

Available Generically: No

Controlled Substance: N/A

Administration Route: Injection, Intravenous

Active Ingredient: Insulin Human Regular

Dosage Form(s): Subcutaneous injection, Intravenous infusion

What Is Humulin R Used For?

Humulin R commonly treats diabetes type 1 and diabetes type 2 in combination with other insulins or other medicines. According to the World Health Organization, in 2014, 422 million people had diabetes (types I and II combined) worldwide. In 2017, 9 million people had type 1 diabetes worldwide. According to the American Diabetes Association, in 2019, 37.3 million Americans (11.3% of the population) had diabetes. Around 1.9 million Americans have type 1 diabetes, including around 244,000 children and adolescents.

Regular insulin is a short-acting insulin. Different people will need different amounts of this medicine, depending on their weight, meals per day, exercise level, etc. Your healthcare provider will supervise any dose change to avoid hypoglycemia (low blood sugar).

Humulin R (Insulin Human Regular) Drug Information - A person with hands on hips with areas affected

Verywell / Dennis Madamba

How to Take Humulin R

Wash your hands before using. Inject into the fatty areas of the skin in your stomach, thigh, buttocks, or outer upper arm area. Use as directed 30 minutes before meals. Rotate injection sites with each shot to avoid lipodystrophy (fat loss in some areas of the body and fat gain in other areas like the liver) or localized cutaneous amyloidosis (abnormal protein growths under the skin). Also keep the following in mind:

  • Do not inject into the area of your skin that’s bruised, thickened, scarred, hard, lumpy, or that has pits or stretch marks.
  • Do not shake your medicine. Do not use if the solution has particles, has changed color, is cloudy, or leaking. Use only if it’s clear and colorless.
  • Do not reuse needles. Needles should be disposed of in a needle/sharps disposal box. When the box is filled, dispose of it according to local regulations. If you have any questions, ask your healthcare provider or pharmacist.
  • Remember to follow your exercise and meal plans recommended by your healthcare provider. Be sure to ask your healthcare provider what to do when you don't eat as much as usual or skip a meal.

U-100 vials:

  • Your healthcare provider can inject U-100 into your vein.
  • Do not draw into a syringe and save for later.
  • Some brands of this medication should not be used in an insulin pump unless your healthcare provider specifically instructs you to do so. If you plan to use an insulin pump, ask your healthcare provider or pharmacist if your brand of insulin can be used in one.
  • If you're using a pump to administer this medication, be sure you know how to use it. Read the package insert or follow your healthcare provider's instructions. 

U-100 cartridges and pens:

  • Do not transfer this medication from a pen to a syringe or combine it with other insulins.
  • As you prepare the dose, this product may make a clicking sound. Do not count the clicks when preparing your dose. If you do, you may use the incorrect dose due to this.
  • Before injecting your dose, remove all pen needle coverings (there might be two). Consult your healthcare provider if unsure about the type of pen needle you have or how to use it.
  • After each shot, remove the needle. Do not store it with the needle attached.

U-500 vials:

  • You will need a specific insulin syringe when using the U-500 vials. To measure and administer your dose, only use that specific insulin syringe. You may mistakenly take the wrong dose of insulin U-500 if you use the wrong syringe. 
  • Do not draw into a syringe and save it for later.
  • Do not combine this insulin with other types of insulin or other liquids in the same syringe.

U-500 prefilled pens:

  • Before injecting a dose of prefilled U-500, remove all pen needle coverings (there may be two). Ask your healthcare provider if you’re unsure about the type of pen needle you have or how to use it.
  • After each shot, remove the needle. Do not store it with the needle attached.
  • Do not transfer this medication from a pen to a syringe or combine it with other insulins.
  • As you prepare the dose, this product may make a clicking sound. Do not count the clicks when preparing the dose. You may use the incorrect dose as a result of this.

U-500 shot product:

  • U-500 insulin is five times more powerful than other brands. It’s best for people who need more than 200 units of insulin per day. 
  • Do not mix or dilute U-500 regular insulin. Only inject it subcutaneously (under your skin). Do not inject it into the muscle or get it into your vein. It’s not recommended for use with an insulin pump, but some people may use it via an insulin pump with strict supervision by their healthcare provider.
  • When measuring a dose, take additional caution. Overdosing by accident might result in serious side effects or life-threatening low blood sugar. 

IV infusion:

  • An IV insulin infusion is given through your vein over a specific time frame determined by your healthcare provider.


Store unopened vials in a refrigerator (36 to 46 degrees F) until the expiration date. Do not freeze. Do not use if frozen. Keep away from heat and light.

Humulin R U-100: Opened vials may be stored for 31 days at room temperature (less than 86 degrees F) or in a refrigerator. Throw out after 31 days from opening.

Humulin R U-500: Opened vials may be stored for 40 days at room temperature (less than 86 degrees F) or in a refrigerator. Throw out after 40 days from opening.

KwikPen: Opened vials may be stored for 28 days at room temperature (less than 86 degrees F) or in a refrigerator. Throw out after 28 days from opening.

Keep your medications out of the reach of children and pets, ideally locked.

If you plan to travel with Humulin R, get familiar with your final destination's regulations. In general, be sure to make a copy of your Humulin R prescription. If possible, keep your medication in its original container from your pharmacy with your name on the label. If you have any questions about traveling with your medicine, be sure to ask your pharmacist or healthcare provider.

Discard all unused and expired drugs, but do not pour them down the drain or toilet. Ask your pharmacist or healthcare provider about the best ways to dispose of this medicine. And check out drug take-back programs in your area.

How Long Does Humulin R Take to Work?

The time it takes to work depends on many factors like:

  • How the medicine was given
  • Where the shot was given
  • How many units were given

It takes U-100 about 30 minutes to start working if given under the skin. If administered into your veins, it takes U-100 between 10 and 15 minutes to begin working. U-500 takes less than 15 minutes to work.

Off-Label Uses

Off-label Humulin is used to treat:

  • Calcium channel blocker or beta-blocker overdose/toxicity
  • Neonatal diabetes mellitus
  • Hyperkalemia

What Are the Side Effects of Humulin R?

This is not a complete list of side effects and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the Food and Drug Administration (FDA) at or 800-FDA-1088.

Common Side Effects

Humulin R may or may not cause side effects in some people. Contact your healthcare provider right away if your side effects do not go away or become irritating. The following are some of the most common side effects of Humulin R:

Severe Side Effects

Contact your healthcare provider right away if you develop any signs of a severe reaction. Call 911 if your symptoms feel life-threatening.

Serious side effects and their symptoms include the following.

Signs of low potassium such as:

  • Muscle cramps
  • Muscle pain or weakness
  • Abnormal heartbeat

Signs of low blood sugar such as: 

  • Headache
  • Shaking
  • Sweating

Other symptoms such as:

  • Chills
  • Severe dizziness
  • Mood changes
  • Seizures
  • Burning or numbness feeling
  • Slurred speech
  • Anxiety
  • Passing out
  • Thick skin, pits, or lumps at the injection site
  • Vision changes
  • Swelling of arms or legs

Report Side Effects

Humulin R may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Humulin R Should I Take?

Drug Content Provided and Reviewed by IBM Micromedex®

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For injection dosage form:
    • For diabetes mellitus:
      • Adults—The dose is based on your blood sugar and must be determined by your doctor.
      • Children—Use and dose must be determined by your doctor.


The following modifications (changes) should be kept in mind when using Humulin R:

Severe allergic reaction: Do not take Humulin R if you’re hypersensitive to regular insulin or any of its ingredients.

Pregnancy: Insulin and food needs are likely to increase as pregnancy continues. Your healthcare provider may increase or adjust your insulin dosage, discuss your food needs, and frequent blood sugar monitoring. Discuss with your healthcare provider if you are or plan to become pregnant.

Breastfeeding: Taking insulin while breastfeeding has not shown low blood sugar in breastfeeding babies. Your food and insulin needs may change during breastfeeding. Talk with your healthcare provider if you plan to breastfeed.

Children: Insulin needs in children may change based on several different factors. Children may also sometimes be unaware when they have low blood sugar. Talk with your child's healthcare provider to discuss any changes needed.

Kidney problems: Frequent glucose monitoring and insulin dose reduction may be needed in people with kidney problems.

Liver problems: Frequent glucose monitoring and insulin dose reduction may be needed in people with liver problems.

Exercise: Exercise tends to lower blood glucose levels. Your insulin may need to be adjusted accordingly.

Illness: Illness may change your blood glucose levels. Your insulin may need to be adjusted accordingly.

Travel: If you plan to travel across more than two time zones, talk to your healthcare provider about any changes needed for your insulin schedule.

Other medications: Insulin requirements may increase if you take medicines that increase blood sugar (e.g., corticosteroids, oral contraceptives, thyroid replacement). Insulin requirements may decrease if you take medicines that lower blood sugar or impact your body's response to insulin (alcohol, antidiabetic agents (blood sugar lowering), salicylates like aspirin, some antidepressants, some kidney and blood pressure medicines, and sulfa antibiotics). It's important to let your healthcare provider know what other medicines you take or plan to take when you're on insulin. This includes over-the-counter, nonprescription products, vitamins, herbs or plant-based medicines.

Missed Dose

If you accidentally forgot your Humulin R dose, take it as soon as you remember. Make sure that you know what to do if you miss a dose. If you are not sure, call your healthcare provider for guidance. Don't try to double up to make up for the missed dose.

Try to find ways to help yourself remember to routinely take the medication that works for you.

Overdose: What Happens If I Take Too Much Humulin R?

Overdose symptoms may include hypoglycemia (very low blood sugar). Severe cases may include seizures or coma.

It's a good idea to have a Glucagon injection pen for cases where your blood sugar may be extremely low. It's important for you—and also for those people you spend a lot of time with—to know how to use a a Glucagon injection in case your blood sugar becomes so low that you became unconscious.

If you think that you're experiencing an overdose or life-threatening symptoms, seek immediate medical attention.

What Happens If I Overdose on Humulin R?

If you think you or someone else may have overdosed on Humulin R, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Humulin R, call 911 immediately.


Drug Content Provided and Reviewed by IBM Micromedex®

Never share insulin needles or syringes with others under any circumstances. It is not safe for one pen to be used for more than one person. Sharing needles can result in transmission of hepatitis viruses, HIV, or other bloodborne illnesses.

It is very important that your doctor check your progress at regular visits, especially during the first few weeks you are using this medicine. Blood tests may be needed to check for unwanted effects.

It is very important to follow carefully any instructions from your health care team about:

  • Alcohol—Drinking alcohol (including beer and wine) may cause severe low blood sugar. Discuss this with your health care team.
  • Other medicines—Do not take other medicines during the time you are using this medicine unless they have been discussed with your doctor. This especially includes nonprescription medicines such as aspirin, and medicines for appetite control, asthma, colds, cough, hay fever, or sinus problems.
  • Counseling—Other family members need to learn how to prevent side effects or help with side effects if they occur. Also, patients with diabetes may need special counseling about diabetes medicine dosing changes that might occur because of lifestyle changes, such as changes in exercise and diet. Furthermore, counseling on contraception and pregnancy may be needed because of the problems that can occur in patients with diabetes during pregnancy.
  • Travel—Keep a recent prescription and your medical history with you. Be prepared for an emergency as you would normally. Make allowances for changing time zones and keep your meal times as close as possible to your usual meal times.

In case of emergency: There may be a time when you need emergency help for a problem caused by your diabetes. You need to be prepared for these emergencies. It is a good idea to:

  • Wear a medical identification (ID) bracelet or neck chain at all times. Also, carry an ID card in your wallet or purse that says that you have diabetes and a list of all of your medicines.
  • Keep an extra supply of insulin and syringes with needles or injection devices on hand in case high blood sugar occurs.
  • Keep some kind of quick-acting sugar handy to treat low blood sugar.
  • Have a glucagon kit and a syringe and needle available in case severe low blood sugar occurs. Check and replace any expired kits regularly.

This medicine may cause serious allergic reactions, including anaphylaxis, which can be life-threatening and requires immediate medical attention. Tell your doctor right away if you have a rash, itching, swelling of the face, tongue, and throat, trouble breathing, or chest pain after you get the injection.

Using this medicine together with other diabetes medicine (eg, thiazolidinedione [TZD] medicine) may cause serious heart problem or edema (fluid retention). Check with your doctor immediately if you are rapidly gaining weight, having, chest pain or discomfort, extreme tiredness or weakness, trouble breathing, uneven heartbeat, or excessive swelling of the hands, wrist, ankles, or feet.

You may have some skin redness, rash, itching, or swelling at the injection site. If this irritation is severe or does not go away, call your doctor. Do not inject this medicine into a skin area that is red, swollen, or itchy.

This medicine may make you dizzy, drowsy, or less alert than you are normally. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.

Too much insulin human regular can cause hypoglycemia (low blood sugar). Low blood sugar also can occur if you use insulin human regular with another antidiabetic medicine, changes in insulin regimen (eg, insulin strength, type of insulin, injection site), delay or miss a meal or snack, exercise more than usual, or drink alcohol. Symptoms of low blood sugar must be treated before they lead to unconsciousness (passing out). Different people may feel different symptoms of low blood sugar. It is important that you learn which symptoms of low blood sugar you usually have so that you can treat it quickly.

Symptoms of low blood sugar include anxiety, behavior change similar to being drunk, blurred vision, cold sweats, confusion, difficulty in thinking, dizziness or lightheadedness, drowsiness, excessive hunger, fast heartbeat, headache, irritability or abnormal behavior, nervousness, nightmares, restless sleep, shakiness, slurred speech, and tingling in the hands, feet, lips, or tongue.

If symptoms of low blood sugar occur, eat glucose tablets or gel, corn syrup, honey, or sugar cubes, or drink fruit juice, non diet soft drink, or sugar dissolved in water to relieve the symptoms. Also, check your blood for low blood sugar. Get to a doctor or a hospital right away if the symptoms do not improve. Someone should call for emergency help immediately if severe symptoms such as convulsions (seizures) or unconsciousness occur. Have a glucagon kit available, along with a syringe and needle, and know how to use it. Members of your household also should know how to use it.

Hyperglycemia (high blood sugar) may occur if you do not take enough or skip a dose of your medicine, overeat or do not follow your meal plan, changes in insulin regimen, have a fever or infection, or do not exercise as much as usual. High blood sugar can be very serious and must be treated right away. It is important that you learn which symptoms you have in order to treat it quickly. Talk to your doctor about the best way to treat high blood sugar.

Symptoms of high blood sugar include blurred vision, drowsiness, dry mouth, flushed, dry skin, fruit-like breath odor, increased urination, ketones in the urine, loss of appetite, stomachache, nausea, or vomiting, tiredness, trouble breathing (rapid and deep), unconsciousness, and unusual thirst.

If symptoms of high blood sugar occur, check your blood sugar level and then call your doctor for instructions.

This medicine may cause low levels of potassium in your blood. Do not use medicines, supplements, or salt substitutes that contain potassium unless you have discussed this with your doctor.

What Are Reasons I Shouldn’t Take Humulin R?

Do not take Humulin R if you’re hypersensitive to regular insulin or any of its ingredients.

Do not use this medicine during episodes of hypoglycemia.

What Other Medications Interact With Humulin R?

Certain medications may affect how well Humulin R works.

Drugs that may increase Humulin R's blood sugar lowering effects:

  • Oral antihyperglycemic (blood sugar lowering) agents
  • Alcohol
  • Antidiabetic (blood sugar lowering) agents
  • Salicylates, like aspirin
  • Some antidepressants
  • Some kidney and blood pressure medicines
  • Sulfa antibiotics
  • Salicylates

Drugs that may reduce Humulin R's blood sugar lowering effects:

  • Atypical antipsychotics
  • Corticosteroids
  • Danazol
  • Diuretics
  • Estrogens
  • Glucagon
  • Isoniazid
  • Oral contraceptives
  • Phenothiazines
  • Protease inhibitors
  • Somatropin
  • Some lipid-lowering drugs (e.g., niacin)
  • Sympathomimetic agents
  • Thyroid replacement therapy

Drugs that may increase or decrease Humulin R's blood sugar lowering effects:

  • Alcohol
  • Beta-adrenergic blockers
  • Clonidine
  • Lithium salts

Pentamidine may cause low blood sugar, sometimes followed by high blood sugar.

Drugs that may mask the signs of hypoglycemia:

  • Beta-adrenergic blockers
  • Clonidine
  • Reserpine

For more detailed information about medication interactions with Humulin R, talk with your pharmacist or healthcare provider.

And be sure to talk with your healthcare provider about any other medicines that you take or plan to take, including over-the-counter, nonprescription products, vitamins, herbs or plant-based medicines.

What Medications Are Similar?

Other insulins used to treat diabetes like Humulin R include:

Note that there are rapid-, short-, intermediate-, long-, and ultra long-acting insulins. It's important to know the differences because they change blood sugar levels differently. They include:

  • Rapid-acting ("bolus") insulin modify blood glucose right at mealtime. It takes about 15 minutes to work after injection. Its effects peaks around an hour or two after injection, and last a few hours after.
  • Short-acting ("regular") insulin is also taken at mealtime. It takes about a half-hour to start working, peaks around three hours, and its effects last up to about six hours.
  • Intermediate-acting insulin takes between two to four hours to work and covers insulin needs for about 12 hours.
  • Long-acting ("basal") insulins modify blood sugar levels in between meals. They take a few hours to start working and can work for up to 24 hours.
  • Ultra long-acting insulin reaches the blood stream in about six hours, doesn't have a peak, and can last around 36 hours or even longer.

Frequently Asked Questions

  • What is Humulin R used to treat?

    It’s used to lower the blood sugar of people with high blood sugar (e.g., diabetes).

  • What is the common side effect of Humulin R?

    Some common side effects include:

    • Weight gain

    • Injection site irritation

  • What should I do if I miss a dose of Humulin R?

    Contact your healthcare provider if you do not know what to do if you miss your dose.

How Can I Stay Healthy While Taking Humulin R?

While Humulin R effectively controls blood sugar, it may be harder to control your levels when you have a fever, an injury, a surgery, or are stressed. Here are a few tips to keep in mind:

  • If there is a change in your health status or if you experience an increase in stress, let your healthcare provider know.
  • Also, tell your healthcare provider before you begin a new diet or exercise regimen, as those changes may affect your blood sugar, for example, like a lower-carbohydrate way of eating.
  • Check your blood sugar the way your healthcare provider tells you to. If your blood sugar is low, do not drive. Driving may increase your risk of having a crash.
  • Remember to wear your medical bracelet as it may be helpful during health emergencies.

Consider working with a team that includes a registered dietitian nutritionist (RD or RDN)—and particularly one that's a Certified Diabetes Care and Education Specialist (CDCES). CDES RDs/RDNs can help you explore your eating, movement, medication habits and more. They can help you build your toolkit and capacity to avoid spikes in blood sugar and help you feel good. Navigating blood sugar control and your eating patterns can be challenging, but you don't have to do this alone.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Food and Drug Administration. Humulin R label.

  2. Qaseem A, Wilt TJ, Kansagara D, Horwitch C, Barry MJ, Forciea MA. Hemoglobin A1c targets for glycemic control with pharmacologic therapy for nonpregnant adults with type 2 diabetes mellitus: a guidance statement update from the American College of Physicians. Ann Intern Med. 2018;168(8):569-576. doi:10.7326/M17-0939

  3. World Health Organization. Diabetes.

  4. American Diabetes Association. Statistics about diabetes.

  5. American Diabetes Association. Insulin basics.

By Queen Buyalos, PharmD
Queen Buyalos is a pharmacist and freelance medical writer. She takes pride in advocating for cancer prevention, overall health, and mental health education. Queen enjoys counseling and educating patients about drug therapy and translating complex ideas into simple language.