The 13C breath test has emerged as a non-invasive, radiation-free method for assessing gastric emptying, offering a practical alternative to traditional scintigraphy. This technique utilizes 13C-labeled compounds—13C-octanoic acid for solids and 13C-acetic acid for liquids—which, after passing through the stomach, are absorbed in the small intestine and metabolized to 13CO₂, detectable in exhaled breath. While widely implemented, methodological variations have impeded standardization. In Japan, the 44th Smooth Muscle Society Workshop proposed a standardized protocol using 13C-acetic acid for liquid meals. We further addressed the lack of gender-specific reference values by establishing Tmax cutoffs of 60 min for males and 75 min for females, revealing no sex-based prevalence difference in delayed gastric emptying among functional dyspepsia (FD) patients. Additionally, daily physical activity was found to influence gastric emptying independently. The Cairn 13C-Spirulina Gastric Emptying Breath Test (GEBT), validated against scintigraphy, offers standardized assessment using 13C-labeled Spirulina and gas isotope ratio mass spectrometry. Despite its clinical promise, the 13C breath test lacks national health insurance coverage in Japan and is hindered by procedural variability and logistical demands. Future efforts should focus on broader standardization, procedural simplification, and integration into routine clinical practice through the support of national insurance reimbursementThe support of national insurance reimbursement.