A urine drug test and a hair follicle drug test differ primarily in detection window, purpose, and what they reveal about substance use. A urine drug test detects recent drug use, typically within the past 1–3 days (longer for some substances like marijuana), making it ideal for identifying current impairment or recent activity. It is commonly used for DOT testing, post-accident testing, and random screenings. In contrast, a hair follicle drug test detects long-term patterns of drug use, typically over the past 90 days, by analyzing drug metabolites embedded in the hair shaft. This makes it more effective for identifying habitual or repeated use rather than recent ingestion. Urine testing is faster and more cost-effective, while hair testing is more difficult to tamper with and provides a broader history of use. Both methods are highly accurate when properly performed, but they serve different purposes depending on whether the goal is to detect recent use or establish a longer-term pattern.