Biomarkers provide objective measures of periodontal disease that can help with early diagnosis, predicting disease progression, and assessing response to treatment. Common biomarkers found in gingival crevicular fluid, saliva, and serum include enzymes, proteins, ions, hormones, bacteria, and inflammatory mediators. Specific biomarkers like alkaline phosphatase, interleukin-1β, C-reactive protein, matrix metalloproteinases, prostaglandin E2, and proinflammatory cytokines like tumor necrosis factor-α and interleukin-6 have been associated with periodontal disease severity and activity. However, no single biomarker can currently be used alone as most provide only limited diagnostic information.