The gut microbiota plays a key role in human health. Dominated by the phyla Firmicutes and Bacteroidetes, its composition is highly individualized and influenced by diet, age, genetics, and the environment. The gut-liver axis highlights the bidirectional re-lationship between the gut and the liver, impacting metabolic homeostasis and immune reg-ulation. Gut dysbiosis, an imbalance in the gut microflora, contributes to liver diseases by disrupting gut barrier function and bile acid metabolism, leading to inflammation and fibro-genesis. Advancements in omics approaches, such as metagenomics, metatranscriptomics, metaproteomics, and metabolomics, have enhanced our understanding of the gut microbi-ota. These approaches offer insights into microbial composition and function, although they vary in cost, efficiency, and complexity. Metagenomics is widely used for its cost-effec-tiveness and rapid turnaround time despite limitations in taxonomic resolution, while meta-transcriptomics, metaproteomics, and metabolomics offer functional and metabolic insights but require sophisticated techniques and expertise. The Firmicutes/Bacteroidetes (F/B) ratio is a potential biomarker of gut dysbiosis linked to obesity, type 2 diabetes mellitus, and liver diseases. However, its diagnostic reliability is debated due to variations in individual factors and a lack of data on its associations with several diseases. Future research should focus on integrating multi-omics approaches so as to provide a holistic view of the gut microbiota and its role in health and disease, aiming for applications in precision medicine. While promising, the F/B ratio should be used cautiously alongside other diagnostic measures. In addition, renewed efforts are needed to develop cost-effective and rapid analysis methods for clinical use.