Insulin has been used in clinical practice for over a century, and while its mode of administration has remained primarily subcutaneous, delivery technologies have significantly evolved, most notably with the development of insulin pens over the past four decades.Today, insulin pens are the leading method of insulin administration globally, used by approximately 60% of insulin-treated patients(¹). Insulin pens are largely popularized due to their ease of use, especially for patients with visual impairments or reduced manual dexterity. They allow for accurate delivery of small insulin doses and offer improved discretion, enabling patients to administer insulin more conveniently and confidently in public settings. Studies have shown that patients using insulin pens tend to have better adherence to therapy and experience fewer hypoglycemic episodes compared to those using traditional vials and syringes. This evolution in insulin delivery not only enhances patient experience but also supports better glycemic management and treatment outcomes (^1,2).

First-Generation Insulin Pens

The initial insulin delivery methods involved large, heavy glass or metal syringes paired with reusable needles, which were cumbersome and intimidating for many patients. For several decades, syringes remained the sole option for insulin administration in clinical practice. However, this method had notable drawbacks such as, poor dosing accuracy, limited social acceptance, and a widespread fear of injections. These limitations not only affected treatment adherence but also compromised patient quality of life. In response to these challenges, insulin pens were developed as a more patient-friendly alternative, offering a simpler, more precise, and socially acceptable mode of insulin delivery(^1-4).

Insulin pens are broadly categorized into two main types(1):

·       Reusable (durable)

·       Prefilled (disposable) pens.

Reusable pens are designed for long-term use, allowing patients to load them with replaceable insulin cartridges as needed. In contrast, prefilled pens come with a pre-installed insulin cartridge and are discarded entirely once the insulin is depleted. Both types are designed to hold up to 3 mL of insulin, and they are capable of delivering doses in increments of 0.5, 1, or 2 units, with some models allowing administration of up to 160 units per injection. To deliver insulin, a separate needle must be attached to the pen before use, ensuring flexibility and sterility for each dose. This structured design contributes to greater dosing accuracy and user convenience compared to traditional vial-and-syringe methods(¹). However, one of the persistent challenges in insulin therapy, particularly for patients with type 1 and type 2 diabetesonmultiple daily insulin (MDI)regimens, ismissing or delaying insulin doses. A recent study involving a Bluetooth-enabled insulin pen cap highlighted this issue, revealing that all participants had missed doses, either intentionallydue to reasons such as inconvenience or irregular eating patterns, or unintentionally, simply due to forgetfulness. The clinical significance of such missed doses is notable; also, previous findings have shown that omitting as few as two meal-related insulin doses per week can result in an HbA1c increase of 0.4%. In response to this, smart insulin pens and pen caps have been developed and are continually being refined to tackle these barriers, offering real-time dose tracking, reminders, and integration with digital health platforms to improve adherence and glycemic outcomes (^1,5).

Smart insulin pens

These are advanced, digitally connected devices that offer capabilities well beyond traditional memory functions. These pens automatically record and transmit critical data, such as the timing and dosage of insulin administration, directly to the user's smartphone through Bluetooth technology. This real-time integration with dedicated mobile applications enables a range of supportive features, including dose reminders, bolus insulin calculators, andelimination of manual logbook entries. By automating and simplifying insulin tracking, smart insulin pens provide a more seamless and user-friendly experience, helping patients manage their insulin therapy more effectively and consistently. Ultimately, these devices address many of the day-to-day adherence challenges associated with pen injectors, promoting better glycemic control and patient engagement(¹).

References:

1.         Masierek M, Nabrdalik K, Janota O, Kwiendacz H, Macherski M, Gumprecht J. The Review of Insulin Pens—Past, Present, and Look to the Future. Front Endocrinol [Internet]. 2022 Mar 8 [cited 2025 May 14];13. Available from: https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2022.827484/full

2.         Kesavadev J, Saboo B, Krishna MB, Krishnan G. Evolution of Insulin Delivery Devices: From Syringes, Pens, and Pumps to DIY Artificial Pancreas. Diabetes Ther Res Treat Educ Diabetes RelatDisord. 2020 Jun;11(6):1251–69.

3.         Vecchio I, Tornali C, Bragazzi NL, Martini M. The Discovery of Insulin: An Important Milestone in the History of Medicine. Front Endocrinol. 2018;9:613.

4.         A Multicenter, Prospective, Observational, Open-Label Study of the Safety and Comfort of Gensulin® Delivery Device Use in a Large Cohort of Adult and Elderly Patients with Type 2 Diabetes [Internet]. [cited 2025 May 14]. Available from: https://www.mdpi.com/1660-4601/17/20/7587

5.         Gorska-Ciebiada M, Masierek M, Ciebiada M. Improved insulin injection technique, treatment satisfaction and glycemic control: Results from a large cohort education study. J ClinTranslEndocrinol. 2020 Mar;19:100217.