Two papers in the Feb. 8, 2023, issue of Cell Host & Microbe have reported new insights into the relationship between myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and alterations in the gut microbiome, and how those relationships change over time. A reliable way to diagnose ME/CFS would be a huge step forward for the study of ME/CFS. Currently, the condition is diagnosed purely by symptoms, which are assessed via questionnaire.