As awareness of driving under the influence of drugs (DUID) increases, enforcement and penalties under the Road Traffic Act have recently been strengthened. Consequently, the number of DUID cases referred to the National Forensic Service (NFS) for toxicological examination has risen, although systematic analyses of the current status in Korea remain limited. This study analyzed DUID cases submitted to the NFS between 2022 and 2025 to identify trends in case numbers and patterns of detected drugs. Blood and urine samples were extracted using solid-phase extraction and analyzed by gas chromatography–mass spectrometry and liquid chromatography–mass spectrometry. During the four-year period, examination requests increased approximately sixfold, from 88 cases in 2022 to 539 cases in 2025. Drug-positive findings accounted for about 75% of cases in 2025. Zolpidem was the most frequently detected substance, followed by alprazolam and flunitrazepam, indicating a high proportion of prescription medications. When classified by drug category, medical prescription narcotics were most common, followed by non-narcotic prescription drugs and illicit substances. These findings suggest that DUID is becoming an increasingly important issue in traffic safety and forensic toxicology, highlighting the need for continued monitoring and scientifically grounded interpretative frameworks.