Nail alcohol and drug testing analyzes substances incorporated into fingernails or toenails, providing a long-term view of alcohol and drug exposure similar to or longer than hair testing. As nails grow slowly, this method can reflect substance use patterns over approximately 3 to 6 months, depending on the type of nail and individual growth rates. Nail testing detects both parent drugs and metabolites, making it difficult to evade through short periods of abstinence. Alcohol use is evaluated through specific biomarkers, such as ethyl glucuronide (EtG), which indicate repeated or chronic consumption rather than incidental exposure. This testing method is especially valuable when hair collection is not possible due to cosmetic, cultural, or medical reasons. Strict chain-of-custody procedures and laboratory confirmation ensure results are accurate, defensible, and suitable for legal or compliance purposes.