Current estimates suggest 9 million to 19 million people worldwide are affected by Hepatitis D virus (HDV) infection, though significant discrepancies in diagnostic guideline implementation across regions and countries indicate these figures may not fully capture the true disease burden. HDV coinfection and superinfection with hepatitis B hasten disease progression, increasing cirrhosis and liver cancer risks, highlighting the importance of early and precise diagnosis. We present a thorough analysis of current and emerging hepatitis D diagnostic methods. Initial diagnosis involves detecting serum anti-HDV antibodies using radioisotope- or enzyme-linked immunosorbent assays. Established techniques like chemiluminescence immunoassay, quantitative microarray antibody capture, and lateral flow assays are being improved. Additional diagnostic markers include HDV antigens and RNA in the serum or liver, detectable through methods like northern and slot blots, fluorescence hybridization, and quantitative real-time PCR. Droplet digital PCR allows quantifying unedited and edited HDV genomes in one sample. Next-generation sequencing offers deeper insights into HDV quasispecies for precise genotyping. Challenges persist, including qualitative diagnostic methods and need for international standards due to lab variability. This review emphasizes the urgency of establishing standardized protocols and international standards for early interventions and reducing the medical burden of chronic HDV infection.