Emerging evidence suggests a link between gut microbiota dysbiosis and osteoporosis. However, specific bacterial taxa and metabolic correlates in human osteoporosis remain poorly characterized. This study explored gut microbial profiles and serum biochemical markers in osteoporosis patients compared to non-osteoporosis individuals in Hainan, China. Fecal samples and serum biochemistry, including liver function, kidney function, lipid profiles, and ion concentrations, were analyzed in six osteoporosis patients and six non-osteoporosis individuals. Gut microbiota composition was assessed via 16S rDNA gene sequencing. Differential abundance analysis and linear discriminant analysis effect size (LEfSe) were performed to identify biomarkers. Osteoporosis patients exhibited significantly higher serum sodium levels (143.31 ± 1.40 mmol/L vs. 140.00 ± 2.60 mmol/L, p < 0.05) and reduced HDL cholesterol (1.03 ± 0.14 vs. 1.33 ± 0.09 mmol/L, p < 0.05). Microbiota profiling revealed 11 enriched and seven depleted bacteria in patients by LEfSe analysis. Notably, Klebsiella showed the highest relative abundance increase in osteoporosis patients, while Megamonas abundance was significantly reduced as indicated by square root of the indicator value (sqrtIVt). This pilot study identifies elevated serum sodium and gut Klebsiella enrichment as potential metabolic and microbial signatures of osteoporosis in the Hainan population. These findings suggest that modulation of gut microbiota and sodium management could be explored as preventive strategies. Larger, multiethnic cohorts and mechanistic studies are needed to validate these biomarkers and elucidate causality.