Drug test detection windows depend on three things: the drug itself, how often you use it, and which sample type is collected. Urine, hair, and fingernail testing each cover very different time windows.
Urine drug tests are the most common and the most affordable. Most water-soluble drugs — amphetamines, cocaine, opiates — are detectable for 2 to 4 days after last use. Benzodiazepines (Xanax, Valium) can persist 3 to 7 days. THC ranges widely: 3 days for occasional use, up to 30 days or more for chronic users. The 5-panel and 10-panel urine screens cover the most common substances.
Hair follicle drug tests extend the detection window to approximately 90 days. They are preferred for situations where a longer look-back matters — child-custody cases, probation monitoring, and some pre-employment screens. Hair tests require about 1.5 inches of head hair (or body hair as an alternative). Same-day instant results are not available for hair; results take 3 to 5 business days.
Fingernail testing covers the longest detection window — roughly 3 to 6 months. It is used when neither urine nor hair is suitable (for example, when a candidate has shaved their head). Nail samples are clipped from all ten fingers and shipped to the reference lab. Results take 5 to 7 business days.
Alcohol has its own short list of tests. A standard urine drug screen does not detect alcohol — that requires a separate breath alcohol test (instant result), ETG urine test (80-hour look-back), or PEth blood test (2 to 4 week look-back).
Key takeaways
- Urine: 2 to 30 days depending on substance
- Hair follicle: ~90 days
- Fingernail: 3 to 6 months
- Breath alcohol: instant; ETG: 80 hours; PEth: 2 to 4 weeks