Cannabis in Blood: How Long Does THC Stay?

The short answer

For most people, cannabis shows up in a blood test for about 1 to 2 days after use. Daily, high-dose users can test positive for around a week, and sometimes a bit longer when a lab looks for metabolites instead of the parent drug. A single hit or one edible is usually closer to the 12 to 24 hour end of that range.

Those numbers are ranges, not rules. Body weight, dose, potency, how often you use, and the specific test all move the window. When someone asks me this, I start with the range and then list the variables.

What a blood test actually measures

Two different things can be measured:

• Delta-9 THC: the active compound. It peaks within minutes of smoking or vaping and drops fast, often to trace levels within a few hours.
• Carboxy-THC (THC-COOH): the main metabolite. It hangs around longer and is what many labs report.

Because of that split, the question has two answers depending on what the lab is looking for.

Typical detection windows

• One-time or rare use: parent THC usually clears in under 24 hours; the metabolite often shows for 1 to 2 days.
• Weekly use: roughly 1 to 3 days for THC, a few days for carboxy-THC.
• Daily use: about 3 to 7 days, sometimes longer.
• Heavy chronic use (concentrates, all-day edibles, high tolerance): up to a week or more for the metabolite in some people.

These windows are population averages. Your own number can land anywhere inside or just outside them.

What stretches or shortens the window

• Frequency and dose: daily use keeps the metabolite topped up.
• Potency: dabs and vape carts deliver more THC than a joint from 1995.
• Route: edibles absorb slower, so blood levels rise later and linger longer.
• Body fat and metabolism: THC is fat-soluble, so it stores in tissue and releases over time.
• Age and liver health: both affect how fast you break the drug down.
• Alcohol or other drugs: can slow metabolism in some cases.

Blood vs urine, saliva, and hair

Blood has the shortest window of the four. Urine can show cannabis for days to weeks, saliva for several hours to a couple of days, and hair for months. If you are facing a specific test, the sample type matters as much as the timeline.

Does a positive blood test prove impairment?

No. Blood THC levels rise and fall fast, and regular users can carry detectable THC without feeling high. Some states use a per se limit (often 5 ng/mL) for driving cases, while others rely on officer observation and field sobriety tests. Federal law still treats cannabis as illegal, and workplace rules vary by employer.

Can you flush THC out of your blood faster?

Not in any reliable way. Drinking water, sweating, sauna sessions, and detox kits do not change how the liver processes THC. They mostly change urine dilution, which labs can flag. Time is the only thing that consistently lowers blood levels.

Getting a real answer for your situation

If the question is legal, medical, or job-related, talk to a lawyer or doctor who knows your state rules. Home tests use different cutoffs than lab tests, and a negative at home does not guarantee a negative at a lab.