t:connect Mobile Bolus

Company: Tandem Diabetes Care
Project: t:connect Mobile Bolus – The ability to deliver insulin from your smartphone
Role: Sr. UX Design Manager
Strategies: UX + UI, user research, user testing, prototyping, team management
Deliverables: UX Workflows, UI design, Detailed documentation and FDA Clearance
Timeline: May 2018 – February 2022
Notable Design Patents: USD864219S1, USD880496S1, USD918227S1


The ability to deliver insulin via smartphone was Tandem’s highest requested feature since the launch of the t:slim X2 in 2012 and only increased in demand when Tandem released their t:connect mobile app in 2020. No other insulin pump on the market had this feature available and Tandem looked to be the first company to deliver it to their users.

design challenge

Create a bolus (insulin delivery) calculator that is easy and intuitive to use. One that existing t:slim X2 customers will be familiar with, and that has an accelerated path to FDA clearance.

  • Priority should be placed on familiar interactions from the t:slim X2, but should take advantage of the screen real estate to make information more clear and reduce the time it takes to complete the delivery of insulin.
  • Safety and efficacy should be considered in every input that affects the calculated dose of insulin.
  • The user must understand the amount of insulin that is calculated at all times.
  • Native OS components should be considered throughout the workflow so that users are familiar with how to proceed based on their experience with other native applications on their smartphone.


The UX Design team worked extensively with the User Research and Human Factors teams to accomplish the following:

  • Determined pain points from the bolus calculator on the t:slim X2 and gathered information on how the experience could be improved using a mobile device.

  • Created designs and prototypes for 7 formative studies, reviewing multiple concepts and interactions for our 8 critical tasks, as mandated by the FDA.

design solution

The UX Design Team decided to keep the familiar layout and interactions of t:slim X2 insulin pump, both for familiarity for existing users and for an accelerated path to FDA clearance based on a predicate device. With the additional screen real estate of the mobile app, we were able to keep Delivery Calculations on the same screen to provide immediate context of the actions taken when entering carbs or glucose, which allowed users to better understand the therapy effects of their choices in real-time.

In contrast to the larger screen size of the Mobile App, the pump requires every keypad entry or informative message to use the entirety of its tiny screen. Cognitively, the user feels like they are leaving the bolus workflow in every instance, adding on to the perceived time it takes to deliver a bolus. Using the Mobile Bolus calculator, the screen real estate allows these keypad entries and informative messages to be accessed within the same screen. The user can now see their entries affect their therapy calculation after each action and perceives the interactions to be happening on a single screen instead of the several screens the pump bolus calculator requires to display.

my role as a Sr. UX Design Manager

The bolus feature of the t:connect mobile app includes 26 workflows, illustrating the multiple ways to calculate a bolus, deliver it to the pump and cover dozens of edge cases to keep the user safe. My role was to design the workflow of each critical task for initial consideration and then work with the lead designer of the project to create prototypes and identify task scenarios to receive feedback from usability studies.

After the initial workflows were complete, I stayed close to the project to review updated workflows from the lead designer as we worked our way through usability studies and regulatory feedback. I coordinated review sessions with UX Design and product, as well as helped define the backlog in which our work would be completed.

ux workflow examples

final screen designs

In addition to the screens below, a demo of the Mobile Bolus feature can be found on Tandem’s YouTube channel here.


The Mobile Bolus feature was an instant success, with 1 million boluses delivered via smartphone within the 1st month of its release. It is the first-ever FDA-cleared smartphone application allowing the initiation of insulin delivery on both iOS and Android. It gives users the freedom to discretely deliver insulin without the use or visibility of their pump and continues to be one of the top selling features for the t:slim X2.