Regular Insulin Injection (Short-Acting Insulin)

Regular insulin is a short-acting human-made insulin. It helps adults and children with Type 1 and Type 2 diabetes control their blood sugar levels. Take regular insulin 30 minutes before you eat a meal. Severe side effects may occur if regular insulin interacts with certain prescription and over-the-counter medications.

What is a regular insulin injection?

A regular or short-acting insulin injection treats diabetes. It uses human-made insulin to lower your blood sugar.

You inject regular insulin under your skin with a needle. Take short-acting insulin 30 minutes before eating a meal. It starts working about 30 to 60 minutes after injection.

Regular insulin is most effective between two and three hours after injection. It reduces your blood sugar for three to six hours after it starts working. When used correctly, an insulin injection helps you avoid serious symptoms of hyperglycemia (high blood sugar).


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What does a regular insulin injection treat?

A regular insulin injection treats diabetes, though it doesn’t cure the disease. It helps children and adults with Type 1 diabetes and Type 2 diabetes.

Insulin is a hormone that helps your body convert glucose (sugar) into energy. People with diabetes either make too little insulin or their bodies can’t use insulin well. Healthcare providers prescribe human-made insulin to control blood sugar levels and avoid diabetes complications.

How does an insulin injection work?

An insulin injection replaces the insulin your body isn’t making or can’t use as it should. Insulin:

  • Lowers your blood sugar levels.
  • Moves glucose from your blood into cells throughout your body so the cells can use glucose as energy.
  • Prevents your liver from releasing too much sugar.


Who should get a regular insulin injection?

Regular insulin injections help children and adults with Type 1 and Type 2 diabetes. Your provider will tell you if this type of insulin is right for you.

What are the types of insulin injections?

There are five types of injectable insulins. Your provider will recommend the most effective type for you based on your lifestyle and your blood sugar levels throughout the day.

Short-acting insulin is a liquid available over-the-counter (OTC) under different brand names:

  • Humulin® R.
  • Novolin® R.

OTC insulins use older forms of insulin (synthetic human insulin), while newer prescription insulins (insulin analogs) better mimic human insulin. You may face different health risks when using these older insulins, so check with your provider first.

Your provider may also prescribe a type of insulin called long-acting insulin along with your regular insulin. Long-acting insulin can help keep your blood sugar controlled for 24 hours.


How is an insulin injection given?

To get insulin into your bloodstream, you can:

Your provider will give you specific injection instructions. Choose a new injection site each time you give yourself regular insulin. Using the same injection site can result in skin lumps, pits and thickening.

You may inject insulin in your:

  • Abdomen (belly).
  • Buttocks.
  • Upper arm.
  • Upper outer thigh.

What are the benefits of a short-acting insulin injection?

Regular insulin controls your blood sugar before a meal. It begins working in about 30 minutes.

What are the risks of a regular insulin injection?

The risks of short-acting insulin include:

  • Hyperglycemia (high blood sugar): Seek immediate help if you have signs of hyperglycemia. These include dizziness, dry mouth and skin, nausea and increased urination.
  • Hypoglycemia (low blood sugar): Seek immediate help if you have signs of hypoglycemia. These include dizziness, confusion and vision changes. To prevent hypoglycemia, make sure to eat about 30 minutes after injecting insulin.
  • Hypokalemia (low potassium levels in the blood): Signs of low potassium include irregular heartbeat, weakness and muscle cramps.
  • Severe allergic reactions: Allergic reactions from regular insulin injections are rare. Seek medical attention immediately if you have signs of anaphylaxis. These signs include severe dizziness, trouble breathing or skin rash or swelling, especially of your tongue, throat or face.

Can you overdose on an insulin injection?

Yes, you can overdose on regular insulin. Call 911 or seek immediate help if you think you’ve overdosed. An insulin overdose can lead to:

  • Severe hypoglycemia (dangerously low blood sugar).
  • Hypokalemia (low potassium levels).
  • Seizures.
  • Coma.

What are the side effects of an insulin injection?

Side effects of a regular insulin injection include:

  • Bumps, pits, swelling, redness or itching at the injection site.
  • Muscle pain.
  • Weight gain.

Serious side effects include:

What interactions should I watch out for?

Many over-the-counter and prescription medications can affect the way regular insulin works or cause serious side effects. Drinking alcohol while taking regular insulin can also be unsafe.

If you have any allergies, talk to your provider. A serious allergic reaction can occur if you’re allergic to any of the ingredients of regular insulin.

Tell your provider about any medications you take, including:

This isn’t a complete list of the medications and supplements that can interact with regular insulin. Talk to your provider before starting a new medication.

How long should you take/use regular insulin?

Your healthcare provider will tell you how long you should take short-acting insulin. They’ll work with you to determine the most effective dose and length of treatment for you. Follow your provider’s instructions carefully to avoid serious side effects.

What should I tell my healthcare provider before taking regular insulin?

Before taking regular insulin, tell your provider if you:

  • Are allergic to any medications.
  • Are pregnant or breastfeeding.
  • Have eye diseases or vision issues.
  • Have episodes of hypoglycemia.

A note from Cleveland Clinic

Regular insulin is a short-acting insulin that helps people with diabetes control their blood sugar. Take this medication about 30 minutes before a meal. If your healthcare provider has prescribed regular insulin, don’t change your dose or stop taking this medication without talking to them. Don’t skip meals or exercise more than usual unless you’ve talked to your provider about adjusting your dose. Changes to what and when you eat, how much you exercise and other medications you take can cause severe side effects.

Care at Cleveland Clinic
Medically Reviewed

Last reviewed on 07/14/2022.

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