Purpose of Review <p>Breath testing to diagnose intestinal microbial overgrowth (MO) is being increasingly utilized, in part due to direct-to-consumer testing modalities. However, the concept of breath testing in the diagnosis of MO is controversial due to numerous limitations regarding optimal substrate, diagnostic thresholds, and confounding variables. We provide seven real-world cases which comprehensively illustrate the principles and nuances of the interpretation of breath testing.</p> Recent Findings <p>We highlight recent studies which examine the optimal substrate for breath testing (glucose versus lactulose), the subtypes and clinical significance of breath test patterns including hydrogen, methane, and hydrogen-sulfide, elevated baseline gas levels, and confounders to breath test interpretation including transit time and diet.</p> Summary <p>Reviewing the latest evidence, we provide recommendations for a personalized interpretation of breath tests utilizing unique patient factors. We conclude with an algorithm to assist clinicians in providing more accurate diagnoses.</p>