This study explores nudging strategies to improve user abilities in order to promote the voluntary return of digital health products, with a focus on the smart pillbox. The two objectives were to create specific design recommendations for the smart pillbox and derive general design guidelines to support a circular lifecycle for future digital health innovations. The study revealed four key design aims: enhancing user abilities, establishing reliable return mechanisms, reducing participation barriers and exploring the wide range of potential applications. The investigation combined thorough analysis, engaging users and refining designs through iterations. The key findings emphasized the crucial factors of product hardware design and strategic communication in influencing users' abilities and willingness to return the smart pillboxes. Innovations in designing smart pillboxes, such as state switches, clear printed instructions, and digital reminders, have been introduced. Preliminary validations suggest that they are effective, but there is a need for further research to explore their combined impacts. Interestingly, this research highlights the importance of "Returners" as crucial stakeholders in the product return ecosystem. This underscores the need for tailored comprehension and design to meet their unique requirements. Although the recommended guidelines have the potential to benefit a wider range of smart health devices, it is essential to validate them with more extensive participant groups. It is worth noting that the current research mostly focused on user ability, however, future studies are encouraged to explore the motivation dimension, which participants identify as a critical factor. This would help create a holistic approach to encourage voluntary product returns. ; DiCE project ; Integrated Product Design