Insulin Pens for Diabetes: A Complete Scientific Guide

For people who require insulin therapy, staying on top of multiple daily injections and getting the dosages right can be an overwhelming task. Insulin pens can make diabetes management easier, more accurate, and less painful, and they are getting easier to use and smarter by the day.

How Insulin Injection Methods Compare

With insulin pens, a cartridge of insulin, which may come filled or need to be inserted, is contained within the pen. The user dials the dosage on the pen, and then the pen injects insulin beneath the skin through a needle. To get the full dose, the pen needle should be “primed” with each use to remove air bubbles by following the manufacturer's directions. The knob of the pen must be pushed all the way in and held at the injection site for 6 to 10 seconds before the needle is pulled out. (Cleveland Clinic provides detailed instructions on how to inject yourself properly with a pen.)

The Benefits of Using an Insulin Pen to Manage Diabetes

“Insulin pens can make administering insulin tremendously easy for a variety of reasons,” says Andrew S. Bzowyckyj, PharmD, CDCES, a pharmacist and the scientific director for the National Kidney Foundation’s kidney learning solutions team, who is based in Hillsboro, Oregon.

How Pens Work to Store and Administer Insulin

Types of Insulin Pens

They come in three distinct formats.

Disposable Insulin Pens

These come with filled insulin cartridges. The entire pen is discarded after all the insulin has been used. Some examples of disposable insulin pens and their price estimates per GoodRx include:

• A Novolog FlexPen containing 300 units of fast-acting (mealtime) insulin aspart has a retail price of $145.87 per pen ($0.49 per unit) and a discount price of $41.12 ($.014 per unit).
• A Toujeo Max SoloStar containing 900 units of long-acting insulin glargine, taken once a day, costs $347.01 per pen retail ($0.38 per unit) and $268.83 with a discount ($0.30 per unit).

Reusable Insulin Pens

These come with replaceable cartridges and are meant to last years. Most reusable pens currently available are now smart pens.

Smart or Connected Insulin Pens

Generally, reusable pens are able to record and transmit data wirelessly, and are often used alongside a mobile app or a continuous glucose monitor (CGM). Functions vary by pen, but the most integrated smart pens log glucose level, carbohydrate intake, and the number of insulin doses administered, says Bzowyckyj.

“Many of these insulin pens sync with an app via Bluetooth technology to help log a lot of these important elements of a person’s care plan,” says Bzowyckyj. “Many times I hear patients say they may not remember if they administered their insulin dose before a meal for a variety of reasons, which then stresses them out because they do not want to double dose and risk hypoglycemia. Not only can insulin pen technology help document doses administered but it can also help patients determine the best dose to administer by factoring in variables such as anticipated carbohydrate intake, active insulin time, and current and goal glucose levels.”

The apps may also track additional health data, such as patient weight and steps or physical activity, either by syncing with a fitness tracker or when the user manually logs the data, Bzowyckyj adds.

“My patients love smart pens,” says Diana Isaacs, PharmD, CDCES, a clinical pharmacy specialist and the director of education and training in diabetes technology at Cleveland Clinic's Endocrinology and Metabolism Institute in Ohio. “For any patient of mine who takes mealtime insulin and prefers not to use an insulin pump, this is a great option and one that I encourage.” (Note that Isaacs receives compensation as a speaker for Medtronic, Dexcom, and Abbott Diabetes.)

Tips for Using Insulin Pens Safely

You can keep unused pens in the refrigerator at 36 to 46 degrees F, then warm them to room temperature when you are ready to use them. Once they are outside the fridge, the expiration date no longer applies.

Recent Developments in Insulin Pen Technology

We asked Bzowyckyj, Isaacs, and Joshua D. Miller, MD, a clinical associate professor of medicine for Stony Brook Medicine in Hauppauge, New York, about the latest developments in insulin pen technology, which include:

• Disposable pens in concentrations of 200 units per mL and 300 units per mL
• The ability to administer partial units for more highly customized doses
• Memory or smart functions that allow users to keep track of when they took insulin
• A dose calculator that allows people to more accurately determine how much insulin they need in a given situation
• The ability to integrate CGM data into a pen

Here’s a closer look at these developments.

Concentrated Insulin

“We’ve seen tremendous improvements in using pens to dose concentrated insulin,” says Dr. Miller. “The pharmaceutical industry has gotten better at packaging those insulins in a safer way to be able to dose the amount of insulin that the patient needs.”

Patients who require higher doses of insulin than the traditional U-100 concentration because they have obesity or have insulin resistance only had U-500 insulin to turn to until recently. U-500 insulin also was previously only available as a vial — now it’s available as a pen, further facilitating dose calculation. “At 5 times the concentration of traditional insulin, it’s very dangerous in an inappropriate amount and without accurate dosing,” Miller says.

Newer pens on the market within the past few years contain varying concentrations of long-lasting (basal) insulin, such as a Tresiba FlexTouch pen with 3 mL of U-200 insulin degludec ($78.20 per pen retail, or $0.13 per unit); and a Toujeo Max SoloStar pen with 3 mL of U-300 insulin glargine ($347.01 per pen, or $0.58 per unit) — prices according to GoodRx. “As a result of the wider availability of some of the concentrated long-lasting insulins, like U-200, patients are able to absorb the insulin in a much more predictable way, and their basal insulin requirements are met more reasonably, accurately, and effectively,” says Miller.

Partial Units

Memory Functions

“For me, the most exciting new development is the dose memory functionality, which keeps track of the doses and times of insulin doses that a person self-administered recently,” Bzowyckyj says. “Oftentimes, it is easy for people to forget whether or not they administered their medications, especially with how hectic our lives can get. With traditional tablets and capsules, people can just check their pillbox to see if today’s space is empty, but unfortunately, that is not an option with insulin. The dose memory feature is a great way to prevent a person from double-dosing their insulin.”

One example is MiniMed’s InPen, which is compatible with Humalog and Novolog insulin cartridges. Prices vary by pharmacy, but the InPen for Humalog has a retail price of $973.97, and the Novolog version costs $1,037.10, according to GoodRx.

Dose Calculators

Isaacs’s patients use the InPen, which she prefers to other pens. For instance, with the InPen, “there is a dosing calculator embedded in it, which makes calculations much easier,” she says. “The calculator makes it much easier to add the insulin needed for a given amount of carbohydrates and a certain glucose level. It may also subtract active insulin from a previous dose that is still working in the body through an advanced calculation.” That last function is one that Miller points out as being especially useful for avoiding dosing errors.

CGM Integration

Despite these developments, some insulin users aren’t even aware that smart pens exist, according to Isaacs. Miller doesn’t see growing awareness necessarily translating into wider adoption of smart pens. Instead, he predicts that insulin users who are interested in technological improvement are more likely to move over to pump therapy rather than smart pens. “The patients I have who don’t want to go on a pump tell me that they want to stay on a [traditional] pen because the pens are simple. The pens are easier to use, and the patient doesn’t have to think about numbers and data. They just dial the dosage, they take it, and they are done.”

He also sees affordability as another barrier to wider adoption. “Outside of rebate programs and coupons, company certificates, and the like, I have not heard of robust insurance coverage from the managed-care and insurance companies to cover electronic pens over the cost of a traditional insulin pen.”

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How to Pick an Insulin Pen With Your Doctor’s Help

So which option is best for you? Isaacs suggests asking your healthcare team the following questions to determine the best fit:

• What are my insulin delivery options?
• What options will insurance cover?
• Would I benefit from having a dosing calculator to help calculate insulin doses?
• Would I benefit from a pen that helps keep track of all insulin doses?
• Would I benefit from a pen that knows when a previous insulin dose is still working in my system?

Insurance coverage will likely drive your choice, says Bzowyckyj. If you have multiple options, consider dexterity (some pens are spring-loaded while others require the ability to extend your thumb to administer the dose), whether you’ll need to administer partial doses, and whether you prefer a disposable pen or a reusable pen that has disposable cartridges, he says.