What Is an Insulin Pen and How Is It Used?

An insulin pen is a disposable or reusable instrument, the size of a marker, used to deliver insulin. A needle is attached to the tip, and insulin is injected subcutaneously (beneath the skin) into fatty tissue.

Insulin is a hormone responsible for bringing glucose to the cells, providing the body with energy. People with diabetes need insulin to control their blood sugar when they do not make any or don't make enough.

Pros of Using an Insulin Pen - Illustration by Theresa Chiechi

Verywell / Theresa Chiechi

Types of Insulin Pens

Insulin pens are prescribed to people with diabetes who take long-acting insulin or multiple daily insulin injections of shorter-acting insulin. There are many types of insulin pens. Some contain different features, while others are allocated for specific insulin types.

Insulin pens vary in price, type of insulin, and dosing. Your insurance may have a specific insulin pen that they have on their formulary (list of preferred prescription drugs).

Some pens are able to deliver half-unit increments, while others deliver insulin in one- or two-unit increments. The lower-dosing pens are often suitable for children with type 1 diabetes who receive smaller doses of insulin. Certain pens can deliver larger doses of insulin in one injection.

Insulin pens can be disposable or reusable.


Disposable insulin pens are prefilled with insulin. The entire pen is discarded once they are finished. Upon opening, these pens usually last 28 to 32 days.


A reusable or refillable pen contains a prefilled, self-contained insulin cartridge that is inserted into the pen device and is replaced once it is fully used or 28 to 32 days have elapsed since the pen was started. Be sure to read the package insert for exact directions. Once the cartridge is thrown away, a new one is inserted to take its place.

Recently, smart insulin pens, or connected pens, which are connected to an intuitive app, have also become available to people with diabetes.

Types of Needles

To administer an insulin injection, pen needles must be attached to the tip of the pen. There are various types of pen needles, which range in length and thickness.

It is recommended to change your needle after each injection. This helps to prevent infection and can reduce pain at the injection site. Needles that are used repeatedly can dull, which can increase pain and potentially reduce the dose accuracy.

All used needles should be thrown away in a sharps container.


Insulin pen needles range in length from 4 millimeters (mm) to 12.7 mm. The lower the number of millimeters, the shorter the needle.

Studies have shown that shorter needles can reduce injection site pain, are less intimidating, and decrease the risk of injecting insulin into muscle tissue.

Needles as short as 4 mm do not appear to impact the function of administered insulin and may have advantages over longer needles. Because they can't reach muscle tissue, they are likely to be less painful.

It was once thought that people who had larger bodies should use longer needles. However, research says that clinicians can recommend using 4-, 5-, and 6-mm needles for all adults with diabetes regardless of their body mass index (BMI).

Some people with diabetes worry that a shorter needle may allow insulin to leak from the injection site, but research has shown this to be an unfounded concern. These needles usually range in thickness from 31 to 32 gauge and do not require pinching the skin to get an accurate dose.

People who are thinner or have less body fat are at increased risk of intramuscular (into muscle) injection with longer needles. If longer needles are needed, they should be injected after pinching the skin or at a 45-degree angle to avoid intramuscular insulin injection.

Intramuscular injection of insulin can increase hypoglycemia (low blood sugar) and glucose variability due to changes in insulin absorption.

While shorter needles may reduce injection pain, improve blood sugar control, and increase insulin adherence, there are times when longer needles may be necessary.

Dr. Tina Cheng, a pediatric endocrinologist at Elmhurst Hospital, tells Verywell, "Longer insulin needles are sometimes used when people with diabetes need to take larger amounts of insulin."

Longer needles have lower gauges, which means a bigger diameter. "The larger diameter of the needle can reduce injection pain. Whereas, if a person were to use a thinner needle, the increased force of a larger dose may increase pain," says Dr. Cheng. Longer needles will require pinching of the skin to get an accurate dose.


Needles range in thickness from 29 to 32 gauge in diameter. The higher the gauge, the thinner the needle. For example, a 29-gauge needle would be thicker than a 32-gauge needle. Most of the longer needles are thicker. The thinnest and shortest, 4mm, 32 gauge, is compared to two strands of hair.


Some pen needles have been formulated to have special edges that may yield a smoother and gentler injection. Always be sure to ask your provider if the pen needle's length and thickness is right for you.

You shouldn't be in pain when giving yourself injections. If you are experiencing pain with injections, you'd benefit from diabetes self-management education or re-education.

How to Use

Proper needle length, injection technique, and site rotation are important considerations for successful insulin injections, which can directly impact diabetes blood sugar control.

If you have not been taught how to use your insulin pen or about the importance of proper injection technique, be sure to visit your medical health professional or reach out to your Certified Diabetes Care and Education Specialist.

Steps for Taking an Insulin Injection

Follow these steps:

  1. The insulin pen should be at room temperature. Injecting with cold insulin can sting.
  2. Wash and dry your hands.
  3. Remove the cap of the pen.
  4. Clean the tip of the pen (rubber stopper) with an alcohol swab.
  5. Attach a new pen needle to the tip of the insulin pen. Twist it on firmly.
  6. Clean your injection site with alcohol and let it dry. Insulin can be injected into the buttocks, abdomen (2 inches away from the belly button), backs of arms, or sides of legs (not into muscle).
  7. Take the protective cap off the needle and set it aside. You will need it to take the needle off and put it in the sharps container.
  8. Using the hand you write with, wrap your fingers around the insulin pen, keeping your thumb free to push down on the knob.
  9. Dial up to two units and squirt insulin into the air. This is referred to as an "air shot," or priming the needle, and preps the needle for a dose (making sure there are no air bubbles). If you do not see insulin come out on your first try, continue to prime the needle until you do.
  10. Dial up to your prescribed dose and insert the needle quickly (but do not jab) at a 90-degree angle into your injection site (depending on the length of your needle, you may or may not need to pinch the skin). The needle should go all the way into your skin.
  11. Slowly push the knob until the full dose is delivered and hold it at the injection site for 10 seconds.
  12. Pull the needle out.
  13. If you bleed a little at the injection site, apply pressure and put on a bandage.
  14. Carefully place the outer cap on the needle to avoid sticking yourself, and unscrew the needle.
  15. Put your used needle in a sharps container.
  16. Put the pen cap back on your pen and store it at room temperature.

Injection Site Rotation

Make sure you rotate your injection sites after each injection. For example, if you are using your abdomen, you can inject insulin into the abdomen multiple times in one day by moving your next injection the width of two fingers over. Rotating injection sites will reduce the risk of lipohypertrophy (lumps of fat forming underneath the skin).

Is An Insulin Pen Right for Me?

Insulin pens can be beneficial for many people with diabetes, but understandably they may not be suitable for all people with diabetes. Diabetes treatment plans should always be individualized and take multiple variables into consideration, including a person's health literacy, financial situation, access to supplies, lifestyle, willingness, and desire of use.


Benefits of an insulin pen include:

  • Mitigate/prevent injection site pain
  • Better accuracy and increased patient satisfaction when compared with vial and syringe
  • Serve as a backup or substitute for those using insulin pump therapy
  • Provide the person with diabetes more freedom, as they are not connected to an insulin pump
  • Portable and easy to travel with
  • Some new models come with a digital application, to help you remember when you last injected insulin and how much was administered.


Drawbacks include;

  • Multiple daily injections can be cumbersome.
  • Pens are susceptible to damage from extreme temperatures—too cold or too hot.
  • People with dexterity issues may have trouble using them.
  • Unless a person is using a smart insulin pen, they will need to be responsible for calculating doses.
  • Pens are usually more expensive than a vial and syringe.


Insulin pens can be used with different types of insulin. Some insulin pens are disposable, while others are reusable. Smart insulin pens have more capabilities than traditional insulin pens.

All insulin pens require attachable needles to deliver insulin doses. Needle sizes range in length and thickness. How much insulin you take, your needle preference, and your body size can determine the type of needle you should use.

A Word From Verywell

If you are a person with diabetes and take long-acting insulin, rapid-acting insulin, or a combination of both, you may be interested in using insulin pens. Insulin pens can increase dose accuracy, are portable, and are generally easy to use.

There are many options to choose from. Discuss your options with your doctor to find out if an insulin pen is the right option for you.

Frequently Asked Questions

  • What type of insulin comes in an insulin pen?

    There are all different types of insulins that are available in insulin pens. Fast-acting insulin, long-acting insulin, and insulin mixtures are all available in insulin pens.

  • Do insulin pens need to be refrigerated?

    Insulin pens should be refrigerated when they have never been used. Once an insulin pen is started, it should be kept at room temperature until it is expired or is finished.

  • Are there side effects to taking insulin?

    Insulin is prescribed to people with diabetes to help control blood sugars. Inaccurate timing of insulin injections, mismanaged calculations of insulin with food, as well as accidental dose mistakes can result in high or low blood sugar. Taking too much insulin can result in hypoglycemia, which needs to be treated right away. Other side effects can include pain at the injection site, lipohypertrophy, and weight gain.

  • How can I check insulin levels?

    Insulin levels can be checked with a blood test.

6 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. Hirose T, Ogihara T, Tozaka S, Kanderian S, Watada H. Identification and comparison of insulin pharmacokinetics injected with a new 4-mm needle vs 6- and 8-mm needles accounting for endogenous insulin and C-peptide secretion kinetics in non-diabetic adult malesJ Diabetes Investig. 2013;4(3):287–296. doi:10.1111/jdi.12035

  2. O'Neal KS, Johnson J, Swar S. Nontraditional considerations with insulin needle length selectionDiabetes Spectr. 2015;28(4):264-267. doi:10.2337/diaspect.28.4.264

  3. Præstmark KA, Stallknecht B, Jensen ML, Sparre T, Madsen NB, Kildegaard J. Injection technique and pen needle design affect leakage from skin after subcutaneous injectionsJ Diabetes Sci Technol. 2016;10(4):914‐922. doi:10.1177/1932296815626723

  4. Al Hayek AA, Al Dawish M. Evaluating the user preference and level of insulin self-administration adherence in young patients with type 1 diabetes: experience with two insulin pen needle lengths. Cureus. 2020;12(6):e8673. doi:10.7759/cureus.8673

  5. Sangave NA, Aungst TD, Patel DK. Smart connected insulin pens, caps, and attachments: a review of the future of diabetes technologyDiabetes Spectrum. 2019;32(4):378-384. doi:10.2337/ds18-0069

  6. American Diabetes Association. Devices and technology: insulin pens.

By Barbie Cervoni MS, RD, CDCES, CDN
Barbie Cervoni MS, RD, CDCES, CDN, is a New York-based registered dietitian and certified diabetes care and education specialist.