Methods  We invited visitors to the cooperating health insurance company, Techniker Krankenkasse, and the German Diabetes Center websites to take part in a web-based randomized controlled trial. The population after randomization comprised 1120 individuals aged between 40 and 70 years without known diabetes, of whom 558 individuals were randomly assigned to the intervention group receiving evidence-based patient information, and 562 individuals were randomly assigned to the control group receiving standard information from the Internet. The primary endpoint was acquired knowledge of elevated blood glucose level issues and the secondary outcomes were attitude to metabolic testing, intention to undergo metabolic testing, decisional conflict and satisfaction with the information.

Results  Overall, knowledge of elevated glucose level issues and the intention to undergo metabolic testing were high in both groups. Participants who had received evidence-based patient information, however, had significantly higher knowledge scores. The secondary outcomes in the evidence-based patient information subgroup that completed the 2-week follow-up period yielded significantly lower intention to undergo metabolic testing, significantly more critical attitude towards metabolic testing and significantly higher decisional conflict than the control subgroup (n = 466). Satisfaction with the information was not significantly different between both groups.

Conclusions  Evidence-based patient information significantly increased knowledge about elevated glucose levels, but also increased decisional conflict and critical attitude to screening and treatment options. The intention to undergo metabolic screening decreased. Future studies are warranted to assess uptake of metabolic testing and satisfaction with this decision in a broader population of patients with unknown diabetes.