Health behavior change is a long and difficult process that persuasive technology supports through persuasion and social influence. Designers, oftentimes, do not distinguish the different social influence factors, one of which is social comparison (the comparison of an individual’s data to that of others). Social comparison is tested by psychologists on health, coping, and wellbeing. However, design guidelines for social comparison features are almost inexistent. This paper explores – through semi-structured interviews - healthcare professionals’ perspectives on technology supporting behavior change, and social comparison. The results present five categories the designers can look into and get inspired. Finally, design implications are presented: three design components for a holistic persuasive design, and three questions related to the social comparison features’ design in order to help with brainstorming and reflection.