Table 1.

Detailed description of app design.

Activity	Aim	Participants	Data collection	Data analysis
Workshops	To develop an app to support young people to self-manage T1DM	Inclusion criteria for young people (and parents): 14-22 years old, T1DM ≥1 year, no psychiatric disorders, in pediatric care or adult care Inclusion criteria for health care providers: on the diabetes team at an adult or a pediatric and adolescent diabetes clinic and with ≥1 year experience working with young people with diabetes	Workshop themes: My diabetes; App functions; Sensitive topics; Future; To my parents; Knowledge and skills; Design and language Brainstorming, prioritizing, feedback, and prototyping were recorded and artifacts collected.	Findings summarized for the IT company to describe functionality and modes of interaction.
App prototyping	To design the first version of the app	IT company; young people with T1DM and parents; health care providers; experts (interactive design students, illustrator, journalist, movie creator)	‒	‒
Mail panel	To ensure a reliable and scalable app	See workshop inclusion criteria.	The participants provided written feedback on prototype versions.	Feedback categorized by themes.
Think-aloud test	To ensure a reliable and scalable app	See workshop inclusion criteria. Could not have participated in previous study activities.	Participants “thought aloud” while performing tasks covering the main functions; recordings and observations.	Feedback categorized by themes.
Feasibility study	To test and evaluate the app in a real-life setting	See workshop inclusion criteria; had participated in think-aloud test.	Young people and health care providers tested the app for 5 weeks and completed questionnaires.	Feedback categorized by themes.