ecent interest in breath methane has demonstrated considerable growth, with a 400% increase in publications per year between 2010 and 2020 compared to the previous decade. This surge has been facilitated by advancements in measurement techniques that have improved both the precision and ease of breath methane analysis. Consequently, there has been a growing appreciation for both the routes of production as well as the physiological effects of methane within the human body, shifting from a perspective of methane as an end-product of GI microbiota to viewing it as a potentially biologically active molecule with exciting potential implications for endogenous processes. The breath methane field stands at a pivotal juncture, where new technologies enable real-time, repeated measures of breath methane for the first time, paving the way for novel insights into personalized methane levels and their interplay with health. This review explores the origins, physiological effects, and measurement techniques of breath methane, highlighting potential pathways for future research.