Cannabis drug tests measure THC metabolites, not THC itself. Urine tests look for THC-COOH. Detection windows depend on the test type, the cutoff, and use history. Most Reddit methods change none of those three.
Detection windows by test type
- Urine: 1 to 3 days after one use. Up to 30 days for daily users. The federal screening cutoff is 50 ng/mL. The confirmation cutoff is 15 ng/mL.
- Oral fluid: 24 to 48 hours. Screening cutoff is 4 ng/mL.
- Hair: about 90 days. A 1.5 inch sample covers that window. Cutoff is 1 pg/mg.
- Blood: hours to 2 days.
Reddit methods that fail
- Water loading. Labs measure creatinine and specific gravity. Creatinine under 20 mg/dL flags a dilute sample. The lab rejects it or asks for a new sample.
- Niacin. Flushing does not clear THC-COOH. Doses above 2 grams cause liver damage.
- Vinegar, bleach, or detergent in the cup. Labs test pH and temperature. Each one flags adulteration.
- Detox drinks. Some mask the screening immunoassay. Confirmatory GC-MS or LC-MS/MS still finds the metabolite.
- Exercise. THC sits in fat tissue. Burning fat can raise urine levels for a short period.
Secondhand smoke and CBD
Secondhand exposure in a closed car can produce a positive result in rare cases. Normal room exposure stays under the cutoff in most studies. Full-spectrum CBD products can contain THC. Labels are not reliable. CBD isolate carries less risk.
What is unknown
No method clears stored THC-COOH fast. Time is the main factor. Results vary with body fat, hydration, and dose. Employers in legal states still set their own rules, and federal law keeps cannabis at Schedule I.