Breath hydrogen tests are popular, noninvasive tests for the assessment of carbohydrate fermentation in patients with irritable bowel syndrome (IBS) and functional dyspepsia (FD). There is limited information regarding the utility of breath hydrogen and methane tests in IBS and FD patients in East and Southeast Asia. This review aims to summarize current literature about common indications of breath testing in this region, the genesis of functional gastrointestinal symptoms by provocative breath testing and provide suggestions for correct use. The most common testing indication is the assessment of lactose intolerance, followed by small intestinal bacterial overgrowth (SIBO) and differentiation of intestinal gas profiles in research setting. Studies in this region not only documented a high prevalence of lactose malabsorption but a population, both healthy and IBS, that is highly symptomatic to typical lactose intakes. Breath hydrogen assessment of other fermentable carbohydrates (FODMAPs) are fairly uncommon, whereas methane breath testing is almost nonexistent. Cumulative hydrogen production following lactulose was also not excessive in IBS patients compared with controls. The evidence however, for the detection of SIBO suggests limited reliability in the use of lactulose or glucose breath testing alone and inconclusive data on its correlation with symptoms. Conversely, little has been carried out in FD. In conclusion, breath testing should be limited in the predicting patients with SIBO for directing clinical management but can be considered in the objective assessment of lactose malabsorption within a low FODMAP diet. Recommendations to improve the interpretation of breath testing in research were also provided.