Weed (marijuana) can stay in your system for varying lengths of time depending on factors like frequency of use, amount consumed, metabolism, and the type of drug test.

• Blood test: THC is detectable up to about 12 hours, sometimes up to 36 hours or a few days in heavy users.
• Saliva test: Detectable for up to 24 hours, sometimes up to 2-3 days.
• Urine test (most common): Detects THC metabolites for 1-3 days after one-time use, 5-7 days for moderate use, 10-15 days for daily use, and up to 30 days or more for heavy or chronic use.
• Hair test: Can detect THC use up to 90 days or three months after last use.

The detection time varies widely based on individual metabolism, body fat, frequency of use, and the sensitivity of the test. For a single use, urine tests might detect THC for up to 3 days, but for heavy chronic users, it may remain detectable for over a month.