I was embroiled in severe insulin pump burnout throughout 2017. My glucose management was relatively stable, but I struggled with technology management issues throughout the year. I had participated in more than half a dozen races, including 5-kilometer and 10-kilometer events and a couple of half marathons, culminating in a marathon. During each of these clutch athletic moments, I had pump failure issues. There was no consistency about when my pump died—only that it did die every single time I raced. Needless to say, I was frustrated.

I have had diabetes for almost 23 years and have used an insulin pump for 14 of those years. For the past 9 years, I have used a leading-brand pump with relatively positive results in terms of both diabetes management and performance in endurance running/cycling/triathlon events. However, the headache of repeated pump failures led me to consider switching back to a multiple daily injection (MDI) regimen to give myself a reprieve from the nuances, and even more so the recent annoyances, of insulin pump therapy. But, I could not let go of my need, or at least my desire, for an automated “brain” that could help do the math calculations for me.

Despite feeling that I had no great option, I took the plunge and switched back to an MDI regimen using disposable insulin pens. I also tried a variety of glucose-tracking mobile applications, such as mySugr (1) and Glucose Buddy (2), as I searched for a tool to help fill in the void left when I stopped using my pump. Although these apps are great for tracking glucose, none of the U.S.-based versions of them possesses the prized insulin-on-board (IOB) functionality I so desperately desired (3) to help me calculate doses. My despair ended, however, when I encountered the InPen.

Produced by Companion Medical (San Diego, Calif.), InPen’s website describes it as follows: “a reusable injector pen plus an intuitive smartphone interface equals smart insulin delivery” (4). InPen was cleared by the U.S. Food and Drug Administration in 2016 and launched in December 2017 (5). I saw a mention of it in a late 2017 email newsletter from the online diabetes community diaTribe, and I immediately jumped on the idea. I talked with my endocrinologist, secured approval from my insurance company, and made the purchase a few days before the start of the new year.

The InPen and its associated app fill a unique niche in the diabetes management landscape and appear to be an option worth considering. However, further analysis of first-hand daily use of the device is warranted.

Table 1 lists notable details about the InPen (4,6). Its initial price is higher than other insulin pens because of its additional features and the accompanying mobile app. It can be used with either insulin aspart or insulin lispro U-100 3.0-mL cartridges and can deliver 0.5–30.0 units of insulin in 0.5-unit increments (4). The pen functions similarly to other insulin pens in terms of insulin capacity, insulin delivery, and ease of use. Individuals who have successfully used disposable insulin pens or pens with cartridge replacements will find the InPen familiar.

TABLE 1.

Highlights of the InPen Smart Insulin Pen System (4,6)

• About half of insurance plans cover it, with copayments ranging from $0 to $75. 
• The cost without insurance is listed as $549 with a coupon. 
• It uses Bluetooth functionality to communicate with a mobile device and has a projected life span of ∼1 year. 
• The app can receive data from Bluetooth-enabled glucose meters. 
• It is approved for use in individuals ≥12 years of age. 
• It works with insulin aspart and insulin lispro U-100 3.0-mL cartridges. 
• It can deliver 0.5–30.0 units in 0.5-unit increments. 
• For now, the app only works with Apple devices with operating system iOS 10 or higher. 
• It is available in blue, gray, or pink. 
• About half of insurance plans cover it, with copayments ranging from $0 to $75. 
• The cost without insurance is listed as $549 with a coupon. 
• It uses Bluetooth functionality to communicate with a mobile device and has a projected life span of ∼1 year. 
• The app can receive data from Bluetooth-enabled glucose meters. 
• It is approved for use in individuals ≥12 years of age. 
• It works with insulin aspart and insulin lispro U-100 3.0-mL cartridges. 
• It can deliver 0.5–30.0 units in 0.5-unit increments. 
• For now, the app only works with Apple devices with operating system iOS 10 or higher. 
• It is available in blue, gray, or pink. 

The life span of the pen is also something to consider. The battery that powers its Bluetooth functionality has a life span of ∼1 year (4). The app provides information about the status of the battery (e.g., “<9 Months Battery Life Remaining”). Although the convenience of the Bluetooth features would be lost at the end of the pen’s battery life, the pen maintains its insulin delivery capabilities beyond that point. Any boluses administered after the battery dies would need to be entered manually within the app, or a replacement pen would be required to regain full functionality.

The unique capabilities of this device are most evident when using the mobile app, as described in more detail below.

The app is free to download immediately, but it is only functional after being paired with the Bluetooth-enabled InPen. Currently, the app is only available within Apple’s ecosystem (4).

Interestingly, once the pen has been paired to the app, if a user chooses to use another type of insulin or prefers disposable pens, there is manual bolus functionality, and the app and its IOB-calculating capacity remain fully operational with this method.

For individuals who are techsavvy and those who have previously used an insulin pump, transition to the pen and its associated app should be a relatively smooth process; the learning curve is minimal. However, for individuals who struggle with the use of technology in everyday life, who have difficulty with the use of a smartphone and the concept of apps, or who have never used an insulin pump, additional education and follow-up may be warranted.

The InPen system offers a series of reminders, including missed dose reminders, long-acting insulin dose reminders, reminders to check blood glucose 2 hours after a dose, and even a reminder to replace the insulin cartridge after 28 days of use (7). It also includes several notification alerts, including insulin temperature alerts and a low-battery icon as the pen reaches the end of its 1-year life span (7). The device ships with an AgaMatrix glucose meter with Bluetooth functionality included in the initial purchase. The auto-upload capability should work with any Bluetooth-equipped meter that will communicate with the Apple iOS environment. To get the most from this pairing function, the glucose meter must be connected to Apple Health and may then pre-populate the blood glucose entry box when using the app’s bolus calculator (7). Because the app integrates with Apple Health (4), it will allow any continuous glucose monitoring (CGM) device paired with the Apple Health system to merge data in the app.

When using the app, there are four main screens—Home, Logbook, Reports, and Settings—each with its own purpose.

  • • Home (Figure 1)

    • ○ Offers an “at a glance” view of several metrics, including the last self-monitoring of blood glucose (SMBG) value, the last dose, and the elapsed time since that dose

    • ○ Shows IOB prominently

    • ○ Includes a button for the dose calculator function (Figure 2); the main differentiator of the app, where glucose values and grams of carbohydrates to be consumed are entered to receive a recommended bolus (or a suggested number of carbohydrate grams to consume), based on previously entered user-specific settings

    • ○ Also includes a button that leads to a Recommendation screen (Figure 3) that details the blood glucose correction, carbohydrate correction, IOB adjustment, and recommended dose

  • • Logbook (Figure 4)

    • ○ Shows average daily blood glucose value, total daily insulin usage, and grams of carbohydrate consumption, as well as SMBG values charted on a graph

    • ○ The bottom half of the screen contains a scrollable listing of each time-stamped event logged throughout the day, including each time a prime or dose was delivered, blood glucose values entered, and recommendations (bolus or carbohydrate) suggested by the calculator

    • ○ Manual doses are entered here

  • • Reports (Figure 5)

    • ○ Provides 7-, 30-, and 90-day average reports with useful metrics such as average blood glucose, recorded high and low blood glucose levels, average usage of carbohydrate and dose calculator, and percentage of dose calculator overrides

    • ○ Reports are convertible to PDF format and easily saved, emailed, or printed from within the iOS environment

    • ○ A dose histogram displaying the number of doses in a set of particular ranges, as well as a modal day plot showing the average dose size, average blood glucose value, and dose count

  • • Settings (Figure 6)

    • ○ A screen where insulin settings are entered, including maximum calculated dose, duration of insulin action, and time of day settings with target blood glucose ranges, insulin sensitivity factors, and insulin-to-carbohydrate ratios

    • ○ Also allows for pairing a new pen device and setting up reminders and provides help and support information, including the pen and app user guides

FIGURE 1.

Home screen.

FIGURE 2.

Dose calculator.

FIGURE 2.

Dose calculator.

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FIGURE 3.

Dose recommendation screen.

FIGURE 3.

Dose recommendation screen.

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FIGURE 4.

Logbook screen.

FIGURE 4.

Logbook screen.

Close modal
FIGURE 5.

Reports screen.

FIGURE 5.

Reports screen.

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FIGURE 6.

Setting screen.

FIGURE 6.

Setting screen.

Close modal

This is the primary differentiator of the InPen system compared to other blood glucose–related apps on the market. This system uses user-determined settings such as personalized carbohydrate factor, correction factor, and target glucose ranges to calculate dose recommendations. When an SMBG value is entered while IOB is still present, the app will also provide a recommendation for grams of fast-acting glucose to consume. Approaches to IOB calculations vary across pump manufacturers, and each company’s formula may be slightly different from those of other companies. The InPen app calculates IOB and carbohydrate recommendations using the formulas shown in Equation 1 and Equation 2, respectively (7).

The capability to process these calculations automatically within the app is an extremely useful feature that previously was only accessible to people who were using an insulin pump. Otherwise, individuals were left to make these calculations manually, which is a truly daunting task for many. For that reason alone, this pen/app combination is worth considering for people who do not have access to or desire to use an insulin pump.

Although this product overall is a good option for people who want to use an MDI insulin regimen while also having the ability to easily calculate IOB-based dose adjustments, there are some potential drawbacks and areas for improvement.

IOB Calculation Limitations

When IOB is still present, entering another SMBG value (e.g., when testing 2 hours postprandially) may result in the app indicating a proposed action to “Eat X grams of ADDITIONAL carbs.” The unfortunate part of this calculation is that it considers all IOB without differentiating mealtime IOB from any correction IOB that may remain active.

It can be argued that not having a way to separate out correction IOB from meal IOB may be a less-than-optimal way to calculate a bolus insulin dose. Perhaps equally troubling is the associated suggestion for carbohydrate correction calculations. Routinely following these recommendations could lead to unnecessary consumption of additional carbohydrates and thus to hyperglycemia. It is therefore advised that users should keep this issue in mind when presented with recommendations for grams of carbohydrate to consume to correct glucose levels.

Data Integration and User Interface Refinement

The CGM integration functionality allows for recorded glucose values to be plotted in the logbook graph but currently does not allow for any analysis of trends or recognition of patterns, such as identifying low blood glucose levels that occur around the same time each day. This limitation could be easily addressed with a future iteration of the app that would allow for some aspect of analysis and data review. In the meantime, CGM users should continue to use their CGM device’s native mobile app or computer software to review blood glucose data and trends.

Some aspects of the InPen system’s reports are extremely useful, such as the dose calculator override information, which may be of interest to a certified diabetes educator or other health care professional seeking to help a user identify, understand, and resolve patterns of low or high blood glucose. This information, especially if coupled with the suggested improvement in analysis of integrated CGM data, may serve as an excellent teaching/learning opportunity for health care providers and their patients who use this system.

However, some of the provided reports seem to have less usefulness in day-to-day diabetes management. The dose histogram, for example, provides information on the number of doses in a set of particular ranges. Although pen doses are limited to 0.5-unit delivery increments, this report gives values in somewhat arbitrary categories (e.g., 0.5–2.0, 2.0–3.6, 3.6–5.2, 5.2–6.7, and so forth) with no additional way to manipulate the report settings. This limitation could also be addressed with a future version of the app.

formula
EQ. 1. IOB recommendation calculation
formula
EQ. 2. Carbohydrate recommendation calculation. A recommendation to “eat X grams” of carbohydrate is given if a value <0 is calculated per this equation.

The pen and app are marketed as a solution for administering all rapid-acting insulin doses. Because all rapid-acting doses would most likely auto-upload from the Bluetooth-connected InPen, it would seem natural to assume that any manually entered doses would be basal insulin. However, when logging a manual dose, the app pre-selects the rapid-acting insulin category, necessitating an additional set for users to switch the category when recording a basal insulin dose. The counter-argument to this complaint is that the app’s focus is on rapid-acting insulin doses and subsequent IOB calculations, so its developers have tried to maintain convenience for users who choose to use another type of rapid-acting insulin pen with their app. Perhaps a future version of the app could provide a user-identified preference in the Settings menu to increase the convenience of the end-user experience.

Product Support and Customer Service

The InPen was submitted to the FDA as a Class 2 medical device, which means that its software verification and validation testing were considered a “major” level of concern (8). With any new technology, especially in the realm of mobile apps, there are likely bugs, but with additional scrutiny in the FDA testing and approval process, it would seem that bugs in a consumer-level medical device should have been eliminated. However, despite an extensive evaluation process related to patients’ understanding of IOB and the functionality of the InPen system, and even a summative usability study to help ensure the device was free of critical errors and safe for use (8), I still encountered a concerning bug in the “Insulin Settings” section. The bug caused some of the settings to change without my input and with no notification of the changes.

This issue required me to contact the company’s customer service department, which led to additional difficulties while using the in-app “contact” method. Despite these major concerns, my call to customer service proved to be a great experience.

Additionally, the app has since been updated to address both of these issues, and I have encountered no further bugs or quirks in my time using the product. As the company continues to update the InPen and its mobile app, maintaining and improving the quality of customer service will be of upmost importance to maintaining a reputation for reliability and relevance within the diabetes community.

So, what is my final verdict on this device? It is definitely an exciting piece of technology that fills a diabetes management niche. The product release in December 2017 was serendipitous timing, given my pump woes. I wanted a break from my pump, but also wanted to keep the IOB functionality it had afforded me; I did not like the prospect of having to self-calculate the math and manually log the data in an effort to avoid insulin stacking and monitor the presence or absence of IOB before exercise. This is currently the only app that offers this IOB functionality and pen-connection combination. For that reason, it is a welcome addition to my diabetes technology arsenal.

That said, it is a new piece of technology from a relatively new company (founded in 2013) (5). Given that, there is uncertainty from a longevity and product-support standpoint, as with any other new device developed by a young company. As in the early days of other diabetes devices, there will likely be some growing pains, especially for early adopters like me.

I believe a piece of technology is beneficial if it can help make diabetes more manageable in my life, which is, after all, the main objective. In my case, the benefits of the InPen system outweigh the limitations because it has allowed me to maintain most of the IOB functionality that I enjoyed with an insulin pump while still switching to an MDI regimen. That does not mean, however, that I don’t hope for future improvements to the app’s functionality, dependability, and user interface that could help secure its place as a truly useful piece of technology in the daily diabetes grind.

No potential conflicts of interest relevant to this article were reported.

B.W.G. is the sole author of this article. He is the guarantor of this work and, as such, had full access to all the data in the manuscript and takes responsibility for the integrity of the data and accuracy of the presented information.

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