Short answer
THC shows up in blood for about 1 to 2 days after one use. A person who uses cannabis several times a day can test positive for up to 7 days. The body breaks THC into carboxy-THC (THC-COOH). That metabolite can stay in blood longer than the parent drug in some cases.
Cannabis Drug Test Detection Times Chart
Detection window by test
- Blood: 1 to 2 days after one use; up to 7 days with heavy daily use.
- Urine: about 3 days after one use; up to 30 days with long-term daily use.
- Saliva (oral fluid): 1 to 3 days.
- Hair: up to 90 days.
What moves the number
- Frequency. Daily or near-daily use raises baseline blood levels and stretches the window.
- Dose and potency. High-THC concentrates and edibles deliver more THC than a low-potency flower sample of the same weight.
- Route. Inhaled THC peaks in blood within minutes, then drops fast. Edible THC passes through the liver, converts to 11-hydroxy-THC, and keeps blood levels elevated for a longer period.
- Body fat. THC is fat-soluble. Fat stores release small amounts back into blood over time.
- Metabolism, age, liver function, and sex affect clearance speed.
Test cutoffs
Labs compare a sample against a cutoff concentration. A blood immunoassay screen at 5 ng/mL and a confirmation step by GC-MS or LC-MS/MS at 1 to 2 ng/mL are common in workplace and forensic testing. A result below the cutoff reports as negative. A person can have THC in blood and still test negative if the level sits under the limit.
What does not work
Water, coffee, exercise, sauna, and detox drinks do not speed THC clearance. THC leaves the body through liver metabolism and excretion. Heavy water intake can lower urine creatinine and trigger a diluted-negative flag on a lab report. No over-the-counter product holds FDA approval to mask a cannabis test.
how long does cannabis stay in your blood
Why an exact number is hard to give
Studies report ranges, not single values. Detection depends on dose taken, test cutoff, lab method, and time since last use. Anyone who needs a firm answer for a legal, employment, or medical reason should ask the testing lab about its cutoff and confirmation method.