Hepatitis B virus (HBV) infection remains a major global public health problem due to its wide geographic distribution, high rate of chronicity, and strong association with progressive liver disease, including cirrhosis and hepatocellular carcinoma. Despite the availability of effective vaccination programs, HBV continues to pose a significant diagnostic and clinical challenge, particularly because many infected individuals remain asymptomatic for long periods. Accurate diagnosis relies on the combined interpretation of serological, molecular, and biochemical markers. This review highlights modern diagnostic approaches for HBV infection, focusing on the clinical significance of serological markers, the role of molecular techniques in disease monitoring, and methods used to assess liver injury severity.