The question of how long cannabis remains detectable in the body is complex and depends heavily on what compound is being measured and by what method. Tetrahydrocannabinol (THC) is the primary psychoactive compound in cannabis, and while its intoxicating effects are short-lived, its chemical signature can persist. The overall duration is not a fixed number but a highly variable range that is influenced by both individual physiology and the sensitivity of the drug screening method used.
How the Body Processes and Stores THC
Once inhaled or ingested, THC rapidly enters the bloodstream and circulates throughout the body. The compound is highly lipophilic, meaning it readily dissolves in fats and oils. This nature dictates how the body handles it, causing THC to be quickly distributed into and stored within the body’s adipose tissue (fat cells) and highly vascularized organs like the brain.
The majority of the THC is metabolized in the liver by a family of enzymes into various breakdown products. The most important of these metabolites is 11-nor-9-carboxy-Δ⁹-tetrahydrocannabinol, commonly known as THC-COOH. While THC itself is responsible for the psychoactive effects, THC-COOH is inactive and is the substance that most standard drug tests are designed to detect.
Since THC-COOH is highly lipid-soluble, it continues to be stored in fat tissue long after the initial effects wear off. From these fat deposits, the metabolite is slowly released back into the bloodstream over time, a process called redistribution. This slow-release mechanism explains why THC metabolites can be detected for days or even weeks, a duration far exceeding that of most other drugs.
Variables That Change Clearance Time
The most significant factor influencing clearance time is the frequency and quantity of cannabis use. For an individual who uses cannabis only once, the compound’s half-life in plasma is relatively short, around one to three days. The time it takes for the body to fully eliminate THC metabolites varies dramatically from person to person, making a single clearance timeline impossible to provide.
For chronic, heavy users, continuous exposure leads to a significant accumulation of THC and its metabolites in body fat. This build-up means the elimination half-life can extend to between five and thirteen days, resulting in a much longer detection window. The potency of the product also plays a role, as a higher dose requires the body more time to process and eliminate the resulting higher concentration of metabolites.
An individual’s metabolic rate directly influences how quickly the liver can break down THC and its metabolites for excretion. Those with a faster metabolism will clear the compounds more rapidly than those with a slower one. This metabolic efficiency influences the overall clearance time.
Body composition is another major physiological variable because of THC’s lipophilic nature. Individuals with a higher percentage of body fat have more storage sites for THC-COOH, causing the metabolite to be sequestered and slowly released over an extended period. Conversely, a lower body fat percentage and higher lean body mass are associated with faster clearance.
Detection Windows for Common Drug Tests
The specific time frame for detection is ultimately determined by the type of sample collected and the target compound it screens for. Different tests look for different substances—either the active THC molecule or the long-lasting, inactive THC-COOH metabolite—which results in vastly different detection windows.
Urine Testing
Urine tests are the most common form of drug screening, and they primarily look for the inactive metabolite, THC-COOH. The detection window for urine is the most variable and depends almost entirely on the user’s consumption habits. For a person who uses cannabis only once, the metabolites may be detectable for approximately one to three days.
If use is moderate (three or four times per week), the detection window typically increases to five to seven days. For individuals engaging in daily or heavy chronic use, the cumulative build-up in fat cells can extend the detection time significantly. Metabolites may be detectable for 30 days or longer after the last use, with some reports extending to 90 days for extremely heavy users.
Blood Testing
Blood tests measure the presence of active THC in the bloodstream, making them an indicator of recent use. Because the body clears active THC from the blood quickly, this method provides a much shorter detection window than urine screening. In occasional users, THC is typically detectable for only a few hours after use, though it may be detectable for up to 12 to 48 hours.
For individuals who use cannabis chronically, the constant replenishment of THC from fat stores can prolong the window. Even in chronic users, however, blood tests usually detect THC for only up to seven days, making them useful for confirming recent consumption rather than long-term history.
Saliva/Oral Fluid Testing
Saliva or oral fluid tests are non-invasive and are primarily used to detect very recent cannabis use, often employed in roadside or on-site scenarios. This test detects active THC and its immediate metabolites transferred to the oral cavity. The detection window is very short, typically ranging from 24 to 72 hours after the last use.
Hair Follicle Testing
Hair testing offers the longest detection window because it measures drug metabolites incorporated into the hair shaft through the bloodstream. This method establishes a pattern of historical use. The standard detection window for a hair follicle test is approximately 90 days, based on the typical growth rate of scalp hair. Hair tests are most reliable for detecting consistent, long-term use and are less effective at identifying single or infrequent instances of consumption.