China has overtaken India and the U.S. as host to the largest diabetic population in the world. Many problems exist in the Chinese healthcare system and very small number of diabetes patients receives treatment. Our paper reports on a case study through the lens of an online diabetes patient community, Sweet Home. We conducted participant observations, text analysis, and interviews, to understand the health management of patients at Sweet Home. Our findings reveal that patients' understanding of diabetes, their choice of treatments, their routine management, and their interactions with others (in the physical world) and among themselves (in the online world) are influenced by many factors: belief in traditional Chinese versus modern western medicine, cultural and social norms regarding social eating and drinking, conflicts over self-images, and responses to comments and pressures of coworkers. That is, social context may significantly affect patients' behaviors and each individual patient's actions may also help reshape the social context. We draw out implications for how our society as a whole may respond to these issues, from the perspective of public health, education, and information technology design.