Inclusion Criteria:  Subject must provide informed consent prior to any study procedures being performed. Subject is a U.S. resident, and speaks and understands English Subject is male or female, ≥ 18 years old. CSID Cases must have been on Sucraid for at the last 12 months. Healthy Volunteers do not have a CSID diagnosis or other chronic gastrointestinal conditions. Subject must have their own Android or Apple device to access the mobile patient app.  Exclusion Criteria:  Females who are lactating or pregnant. Subjects with allergy to sucrose. Subjects with causes of abdominal pain or altered bowel habits other than symptoms -related to CSID (in CSID group) such as SIBO, IBD, celiac disease, pancreatitis, or -gastrointestinal bleeding. Diabetes mellitus. Use of systemic antibiotics, had a barium study, colonoscopy, unexplained runny diarrhea, or similar within 14 days prior to informed consent. Potential subjects can be re-screened once they meet this criterion. Recent febrile illness. Subject has major physical or psychiatric illness within the last 6 months that in the opinion of the investigator would affect the subject's ability to complete the trial.