Increasing evidence points to gastrointestinal dysbiosis as a major component of the pathogenesis of post- and long-COVID gastrointestinal symptoms. Microorganisms included in the intestinal microbiota may influence the functioning of the gastrointestinal tract through inter alia short-chain fatty acids (SCFA), lipopolysaccharide (LPS), as well as gases such as hydrogen, methane, or hydrogen sulphide. The identification of the particular dysbiosis type has become a major challenge recently, because the proper dysbiosis determination may contribute to optimization of the treatment of diseases related to the dysfunction of the brain-gut-microbiota axis.