How Long Does Cannabis Stay in Your System?
Cannabis clears urine in 3 days for casual users and 30+ days for daily users. Blood takes 1 to 2 days, saliva 1 to 3 days, hair up to 90 days.
Quick answer
If you use cannabis, you might wonder how long THC stays detectable. The short answer: blood tests usually detect THC for 1 to 2 days after occasional use. For heavy, chronic users, that window can stretch to 7 days. Hair tests are different. They can pick up THC for up to 90 days, which is about three months.
How blood tests work
Blood tests look for delta-9-tetrahydrocannabinol (THC) itself. They also look for its metabolites, like 11-hydroxy-THC and carboxy-THC. THC levels peak within minutes of smoking or vaping. Then they drop fast. For someone who uses once, THC is often gone from blood within a few hours. But the metabolite carboxy-THC lingers longer. That's why a blood test can stay positive for a day or two. In chronic users, carboxy-THC can be detected for up to a week. Edibles and concentrates may extend the window because they deliver more THC.
How hair tests work
Hair tests rely on THC and its metabolites getting trapped in the hair shaft as it grows. Hair grows about half an inch per month. So a standard 1.5-inch sample can cover roughly 90 days of use. That's why hair tests have a much longer detection window than blood. Once THC is in your hair, it stays there. Shampoos, bleaches, and home remedies do not remove it. Body hair grows slower, so a body hair test might cover a longer period, but it's less common.
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What changes the timeline
- Frequency of use: Daily users build up more metabolites, so blood and hair tests stay positive longer.
- Metabolism: People with faster metabolism clear THC and its metabolites quicker.
- Body fat: THC is stored in fat. More fat means a slower release and a longer detection window.
- Product potency: High-THC concentrates and edibles can push detection times out.
- Test sensitivity: Different labs have different cutoff levels. A more sensitive test can catch lower amounts.
Can you flush THC from your system?
You'll see a lot of advice about detox drinks, niacin, and saunas. Most of it doesn't work for blood or hair tests. Blood tests are hard to beat because the window is already short. For hair, no shampoo has been proven to remove THC. The only sure way to pass a test is to stop using cannabis long enough for your body to clear it. That means at least a week for blood, and up to 90 days for hair. If you're a heavy user, give yourself more time.
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Bottom line
Blood tests catch recent use, usually 1 to 2 days, up to 7 for heavy users. Hair tests catch use over the past 90 days. The exact timeline depends on how much you use, how often, and your own biology. If you have a drug test coming up, the safest bet is to stop early and stay hydrated. But no method is foolproof. Know the test you're facing, and make a plan.