Background/Aims: An increase in postprandial intestinal gas plays a role in bloating symptoms. We aim to study the utility of spot breath hydrogen (H 2 ) level in predicting the response to a low fermentable oligo-, di-, mono-saccharides, and polyols (FODMAPs) diet. Methods: Patients with functional gastrointestinal disorders diagnosed by Rome IV criteria with bothersome bloating for > 6 months were prospectively enrolled. Patients completed 7-day food diaries and collected a breath sample 2 hours after their usual lunch at baselineand 4 weeks after low FODMAPs dietary advice by a dietitian. The responder was defined as an improvement of ≥ 30% bloatingscores in the fourth week. Results: Thirty-eight patients (32 female, 52.6 ± 13.8 years; 22 irritable bowel syndrome) completed the study. Twenty-one patients (55%) were classified as responders. Baseline global gastrointestinal symptoms, bloating, abdominal pain scores, and numbers of high FODMAPs items were similar between responders and non-responders. Both groups significantly decreased high FODMAPs items intake with similar numbers at the follow-up. The area under the curve for predicting low FODMAPs responsiveness using baseline H2 levels was 0.692 (95%CI, 0.51-0.86; P < 0.05), with the best cutoff at 8 parts per million (sensitivity 66.7%, specificity 82.4%). 66% of responders had baseline H2 level > 8 parts per million vs 17% of non-responders (P < 0.05). The baseline spot hydrogen level in responders was 9.5 (3.3-17.3) vs 4.5 (3.3-6.3) in non-responders (P< 0.05). Conclusions A higher baseline breath hydrogen level was associated with bloating improvement after low FODMAPs dietary advice. A spot breath test after lunch, a simple point-of-care test, is possibly helpful in managing patients with bloating.