4.2.1. Participants

Twenty-one adolescents with Type 1 diabetes participated in a pre-pilot (*n* = 7) and pilot study (*n* = 14). Participants were registered patients at the pediatric diabetes department from the Gelderse Vallei Hospital in Ede (the Netherlands). The first group of participants was allocated to a pre-pilot study in September 2016 and the second group of participants was allocated to a subsequent pilot study performed during October–December 2016. Participants were included if they fulfilled the following inclusion criteria: (a) diagnosis of Type 1 diabetes for at least six months; (b) between 12 and 18 years of age; (c) written informed consent provided by adolescents themselves and one of their parents (or legal guardians); (d) availability of an Android smartphone with an internet/data connection

and (e) a reasonable level of understanding of the Dutch language. If the adolescent did not have an Android smartphone available, they were provided with a phone that satisfied system requirements.
