In recent years, social networking sites and online communities have served as alternate information sources for patients, who use social media to share health and treatment information, learn from each other’s experiences, and provide social support. This research aimed to investigate what patients with Inflammatory Bowel Disease (IBD) are talking about on Twitter and to learn from the experimental knowledge of living with the disease they share online. We collected tweets of 337 IBD patients who openly tweeted about their disease on Twitter and used the Natural Language Understanding (NLU) module by IBM Cloud to apply category classification and keywords extraction to their tweets. To evaluate the results, we suggested a method for sampling the general population of Twitter users and forming a control group. We found statistically significant differences between the thematic segmentations of the patients and those of random Twitter users. We identified keywords that patients frequently use in the contexts of health, fitness, or nutrition, and obtained their sentiment. The results of the research suggest that the personal information shared by IBD patients on Twitter can be used to understand better the disease and how it affects patients’ lives. By leveraging posts describing patients’ daily activities and how they influence their wellbeing, we can derive complementary knowledge about the disease that is based on the wisdom of the crowd.