t:slim X2 Insulin Pump


Company: Tandem Diabetes Care
Project: t:slim X2 Insulin Pump
Role: Sr. UX Designer
Strategies: UX + UI, user research, user testing, prototyping
Deliverables: UX Workflows, UI design, Detailed documentation and FDA Clearance
Timeline: September 2009 – December 2011, ongoing through the release of Control-IQ in 2020
Notable Design Patents: US-20130283196-A1, US-20140276419-A1, EP2724739B1


Insulin pumps are difficult to learn and cumbersome to interact with.

  1. Users are overwhelmed with the training it takes to use an insulin pump and are overwhelmed with the time and effort it takes to manage their diabetes.

  2. Users are afraid of pump therapy because of the risk of accidental overdose or other errors that lead to harmful therapy. They are embarrassed to be seen with an insulin pump by their peers and they are frustrated by the current insulin pumps on the market that feel antiquated and out of touch with modern technology. 

  3. Tandem wanted to enter the diabetes market with a world-class pump in design, form factor and an easy to use, intuitive user experience.

design challenge

Create an insulin pump with better design that can reduce or prevent user error. To make a better insulin pump, Tandem needs to optimize the design of the user interface and create a device that feels modern, sleek and offers an exceptional user experience.

  • Priority should be placed on reducing the number of steps and buttons it takes to complete critical tasks in starting and defining personal therapy settings, the start and stop of insulin, and delivering a bolus without error.
  • The user interface design should be modernized to look like popular touchscreen devices and applications. The user should be proud of the technology in their pocket and not embarrassed of an antiquated design and interface.
  • Edge cases and other interactions that could initiate harmful therapy should be addressed with user-friendly messaging and clear instruction on how to address the issue.


I worked extensively with the User Research and Human Factors teams to accomplish the following:

  • Determined pain points from users with existing insulin pumps and gathered information on what was needed to simplify their experience.

  • Created designs and prototypes for over 2-dozen formative studies, reviewing interactions in over 100 screen designs for our 17 critical tasks, as mandated by the FDA.

  • Supported the FDA Summative Study across 5 major US Cities, viewing participants and recording data to validate the design as safe and efficient to use, based on the criteria of the FDA and our regulatory strategy.

design solution

Through our usability studies one of the most important things I learned was the importance of providing clear touch targets for entry keypads and other sensitive areas when making therapy decisions. Our solution was to increase our touch targets by 50% on most screen areas, which while that led to less information on a single screen, we found that users didn’t mind additional button presses to get where they were going, so long as the screen was intuitive and the path forward was clear. We also developed what we called “Dynamic Error Handling” which would disable numbers in a keypad when it would result in an entry outside our range of safety (see middle screen below).

This played against one of our primary goals of reducing button taps, but we learned that as long as the information was clear and informative, users felt safer seeing that their entry was verified, or that they could adjust an error in-flow instead of discovering the error later in therapy.

ux workflow examples

The t:slim X2 has over 300 screen designs spread across 18 interaction design workflows. Below are two workflow examples of the complexity that was required to keep our users safe if therapy values were entered incorrectly, or the user was otherwise presented with entries that could negatively impact their therapy. My primary role was to not only execute these workflows for the user, but to illustrate a clear path for every outcome so that development could implement our solutions without error. 

final screen designs

For the full experience of the t:slim X2, you can download the t:simulator for your iPhone or Android device to navigate every screen and interact with every feature.


The original t:slim was launched in 2012 and the current t:slim X2 is considered the most user-friendly pump on the market. With the support of Tandem’s insulin controlling algorithms Basal-IQ and Control-IQ, users are living their lives better than ever before.