Insulin Pen

insulin pen


An insulin pen is a convenient and discreet method for diabetes patients to take prescribed insulin medication. These devices resemble a fountain pen and are disposable or have replaceable insulin cartridges.

A short, thin needle at the end of the pen is used to inject the insulin. A small dial allows the individual to select the exact dosage needed. Pens carry 150 or 300 units of insulin.

Insulin pens may be a good option for diabetes patients who are traveling, and can be used and stored easily at work or school. Their convenience and ease of use also may make them good options for certain populations, such as children and elders.

About insulin pen

Insulin pens are devices that resemble a fountain pen and are used by diabetes patients to self-administer insulin that their physician has prescribed. These pens come in two forms:

  • Disposable. Patients use these pens, then dispose of them once the medication is used up.

  • Reusable. Patients load these pens with replaceable prefilled insulin cartridges that provide the medication.

Insulin pens are used with a short, thin needle that is attached to one end of the pen. A small dial on the pen allows patients to select the exact dosage of medication needed. Patients press a plunger at the end of the pen that delivers a dose of insulin just under the skin.

Insulin pens typically hold 150 or 300 units of insulin (1.5 or 3 milliliters). Needles may range from half an inch to less than one-third of an inch (as little as 5 millimeters), with a gauge of 29 to 31. The higher the gauge number, the thinner the needle.

Pens may deliver doses as little as half a unit and up to dozens of units. The dosage of insulin depends on a physician’s prescription.

Insulin pens have many advantages. They are easily carried and can be used discreetly in situations away from home, such as during travel or at work or school. Patients do not need to draw insulin from a bottle, and the dosage dials make it easier for some people with diabetes to deliver accurate dosages of insulin. The needles used with insulin pens are short and thin, and therefore less likely to cause discomfort. Some research has found that switching from syringe injections to an insulin pen may improve compliance, reduce hypoglycemia and other complications, and yield significant long-term savings.

According to the American Diabetes Association, insulin pens are accurate and convenient and may especially benefit people who are active, are on a multidose insulin regimen or have impairments in coordination or eyesight.

However, insulin pens also come with some drawbacks. They are generally more expensive in the short term than syringes, which remain the most common form of insulin delivery. Patients usually have to waste a unit or two when priming the pen before use, and some insulin is often left over when pens or cartridges are thrown away.

In addition, not all insulin types are available in insulin pens, and patients using these devices cannot mix insulin types. People who use two types of insulin must inject each separately if using an insulin pen.

Insulin pens have become widely accepted by people with diabetes in many countries but are used less frequently in the United States. Possible reasons for low usage in the United States include difficulties with insurance reimbursement and lack of knowledge among patients and healthcare providers.

Even among people with diabetes who normally get insulin from another source, an insulin pen may be used as a backup if an insulin pump malfunctions or there is a problem with a syringe.

Types and differences of insulin pens

Insulin pens come in either reusable or disposable form:

  • Reusable pens. Patients load these pens with replaceable insulin prefilled cartridges that provide the medication. Cartridges are sold separately and often come in packs of five, with the cartridges holding 150 or 300 units of insulin. Depending on dosage requirements, an individual cartridge can provide up to several days’ worth of insulin for a patient. Once the insulin in a cartridge is used up, the patient disposes of the cartridge and replaces it with a new one. Reusable pens can last for years if properly maintained.
  • Disposable pens. Patients use these pens, then dispose of them once the medication is used up. Disposable pens usually come in packs of five, with each pen holding 300 units of insulin. They often are considered more convenient than reusable pens, but generally cost more.

There are many factors that patients should take into account when deciding what kind of pens to buy. These include:

  • Brands and types of insulin available. Cartridges can be prefilled with the following types of insulin, according to the American Diabetes Association: regular, NPH, insulin lispro, insulin aspart, 70/30 premixed insulin or 75/25 premixed insulin.
  • Maximum number of insulin units a pen holds. This may range from 16 to 70 units.
  • Largest dose that can be injected.
  • How finely the dose can be adjusted. Some pens allow two-unit increments (2, 4, 6, etc.) whereas others allow one-unit or half-unit increments.
  • How the pen indicates whether or not there is enough insulin left for an entire dose.
  • Size of markings on pen’s dose dial. On some pens, these numbers are magnified, which can help people whose vision is mildly impaired by diseases such as diabetic retinopathy, glaucoma or cataracts. However, people with vision loss may need assistance using an insulin pen or other method of insulin delivery. 
  • Ease of operation.
  • How the pen allows for dosage corrections when a patient makes an error.
  • Style and appearance of the pen and whether the pen is metal or plastic.

Using insulin pen

Patients preparing to use an insulin pen are advised to follow the manufacturer’s directions. The following steps are typically involved:

  • Gather supplies.
  • Wash hands.
  • Prepare the pen by removing the pen cap and verifying that the insulin is the type the doctor prescribed. Patients should also check to make sure the insulin has not expired and that it is not discolored, frosted or lumpy.
  • Attach a needle to the pen according to the manufacturer’s directions.
  • Mix the insulin well by rolling the insulin pen between the palms of the hands or tipping the pen back and forth at least 10 or 20 times.
  • Prime the pen by shooting it into the air once to make sure it is working properly.  To do this, take the following steps:
    • Set the dosage dial on the pen for one or two units of insulin.  
    • Hold the pen like a pencil with the needle pointing up.
    • Tap the barrel to let air bubbles in the insulin cartridge float to the top of the cartridge.
    • Push down on the pen’s injector button and shoot a small amount of insulin into the air. A couple of drops of insulin should come out of the needle. If nothing comes out, try another air shot. If insulin still does not appear, the pen may be low on insulin, or the needle may not be connected properly.
  • Use the dial to deliver the required dosage of insulin. The pen is now loaded and ready to use.
  • Choose an injection site. Sites often used include the abdomen, upper arms, thighs and buttocks. Avoid sites near a mole, scar or injury or within 2 inches (about 50 millimeters) of the navel. It is good practice to rotate the injection site, which will help prevent damage to skin tissues.
  • Make sure the site is clean. Clean the area with soap and water or alcohol and let it dry.
  • Pinch up a fold of skin and insert the needle at a 90-degree angle.
  • Firmly press the insulin pen injection button. The injection should take a couple of seconds, unless taking a very small dose. Let go of the skin.
  • Pull the needle straight out and gently press on the injection site with a finger for a few seconds. Do not rub or massage the skin where the insulin is injected.
  • Once finished with the injection, remove the needle to prevent air from coming into an attached needle or allowing insulin to leak out.

Patients should follow the manufacturer’s recommendations for storage. Typically, pens not yet used are stored in a refrigerator and are good until the expiration date, and pens that have been used are stored without the needle at room temperature for 10 days to four weeks, depending on the type of insulin used. Patients needing clarification are advised to consult the manufacturer or their physician or certified diabetes educator.

Questions for your doctor on insulin pen

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about insulin pens:

  1. Are insulin pens an option for me?
  2. Can I use one even if I take more than one kind of insulin?
  3. Can I use one by myself if I have poor eyesight or impaired coordination, or will I need help?
  4. What are their advantages over other methods of insulin administration?
  5. What are their disadvantages?
  6. What should I look for when buying an insulin pen?
  7. Do you recommend any particular type or brand of insulin pen for me?
  8. What gauge and length of needle is needed for my insulin pen?
  9. How should I store my insulin pen?
  10. How long may I keep a used pen at room temperature?
  11. What storage temperature is too high or low for my insulin pen?
  12. How should I dispose of a needle or insulin pen?
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