How long does cannabis stay in the system?

From the Guidelines

Cannabis can stay in your system for varying lengths of time, typically ranging from a few days to several weeks or even months, depending on factors such as frequency of use, metabolism, body fat percentage, and potency of the cannabis consumed. The duration of cannabis detection in the system varies widely based on the method of testing, with urine tests detecting THC for 3-4 days in occasional users and up to 30 days or longer in frequent or heavy users 1. In blood, cannabis is usually detectable for 1-2 days, though this can extend to 7 days with heavy use. Hair tests can detect cannabis for up to 90 days, while saliva tests typically show cannabis use for 24-72 hours.

Factors Influencing Detection Time

• Frequency of use: Frequent or heavy users may test positive for longer periods than occasional users
• Metabolism: Individual metabolic rates can affect how quickly THC is broken down and eliminated from the system
• Body fat percentage: THC is fat-soluble, meaning it's stored in fat cells and released slowly over time, which is why it can remain detectable longer in people with higher body fat percentages
• Hydration levels: Hydration can affect the concentration of THC in urine and other bodily fluids
• Potency of cannabis: More potent cannabis may result in longer detection times

Testing Methods

• Urine tests: Typically detect THC for 3-4 days in occasional users and up to 30 days or longer in frequent or heavy users
• Blood tests: Usually detect cannabis for 1-2 days, though this can extend to 7 days with heavy use
• Hair tests: Can detect cannabis for up to 90 days
• Saliva tests: Typically show cannabis use for 24-72 hours It's essential to note that THC is stored in fat cells and released slowly over time, which is why it can remain detectable longer in people with higher body fat percentages or those who use cannabis regularly 1. Different testing methods have different detection thresholds, with hair tests being the most sensitive for long-term detection and blood tests better for identifying recent use.

From the Research

Detection Times for Cannabis in Different Biological Matrices

• The detection time for cannabis in the system can vary depending on the biological matrix being tested, such as blood, urine, or oral fluid 2, 3, 4, 5, 6.
• In general, cannabis can be detected in urine for several days to several weeks after last use, with heavier users tend to have longer detection times 4, 6.
• The detection time for THC in oral fluid can range from a few hours to several days, with a study finding that THC was detectable in oral fluid for up to 8 days after admission 3.
• Blood THC levels can be detectable for several days after last use, with one study finding that THC was detectable in blood for at least 7 days in some subjects 2.

Factors Affecting Detection Times

• The frequency and amount of cannabis use can affect the detection time, with heavier users tend to have longer detection times 4, 5.
• The potency of the cannabis preparation can also affect the detection time, with more potent preparations tend to have longer detection times 6.
• The specific gravity of the urine specimen can also affect the detection time, with more concentrated urine specimens tend to have longer detection times 4.

Analytical Methods for Detecting Cannabis

• Immunoassays are commonly used for detecting cannabis in urine, but they can have varying sensitivity and specificity depending on the assay and cutoff concentration used 6.
• Gas chromatography-mass spectrometry (GC-MS) is a more sensitive and specific method for detecting cannabis in urine, but it is also more expensive and time-consuming 6.
• The choice of analytical method can affect the detection time, with more sensitive methods tend to have longer detection times 5, 6.