The 150 nanograms per milliliter (ng/mL) threshold measures the concentration of cannabis metabolites in a urine sample. While the most common initial screening cutoff is 50 ng/mL, the 150 ng/mL level represents a much higher concentration. This higher cutoff is often used in specific professional or athletic testing protocols, or as a marker for heavy usage. A positive test result signifies that the concentration of the target metabolite meets or exceeds 150 ng/mL. The time it takes to drop below this point is highly variable among individuals.
How the Body Processes THC Metabolites
The substance measured in urine drug tests is not the psychoactive compound delta-9-tetrahydrocannabinol (THC), but its main inactive metabolic byproduct, 11-nor-9-carboxy-THC (THC-COOH). After THC enters the bloodstream, the liver quickly metabolizes it using cytochrome P450 enzymes. This process converts THC into the active metabolite 11-hydroxy-THC, which is then oxidized into the inactive THC-COOH.
The elimination of THC-COOH is slow because THC is highly lipid-soluble, meaning it readily dissolves in fat. This high lipophilicity causes THC to be rapidly absorbed and sequestered by the body’s adipose tissue. With repeated use, THC accumulates in these fat deposits, and the metabolites are slowly released back into the bloodstream over time for final processing and excretion.
The body eliminates metabolites primarily through the gastrointestinal tract, with up to 80% excreted via feces. The remaining fraction, roughly 20% to 35%, is excreted in the urine, mainly as a glucuronide conjugate of THC-COOH to increase water solubility. This slow, two-part elimination process—storage in fat followed by gradual release—allows THC metabolites to be detected in urine for an extended period after the psychoactive effects have worn off.
Factors That Determine Clearance Speed
The speed at which THC-COOH concentration drops below 150 ng/mL is governed by biological and behavioral factors unique to each person. The most significant variable is the frequency and duration of use, which directly affects the saturation level of THC-COOH in fat stores. A single use results in minimal fat saturation and a rapid decline in concentration. Conversely, chronic, heavy use leads to substantial accumulation, requiring a much longer clearance time.
Body composition plays a major role because THC is fat-soluble. Individuals with a higher body fat percentage possess more storage space for the metabolites. This allows the compounds to be sequestered and slowly released over a longer period. Consequently, two people with the same usage pattern but different body fat percentages will likely have different clearance timelines.
The individual metabolic rate further dictates how quickly liver enzymes process metabolites released from fat tissue and how fast the body can excrete them. Genetic variations in liver enzyme activity, specifically those related to the cytochrome P450 complex, influence the efficiency of this breakdown process. A person with a naturally faster metabolism will clear the metabolite concentration more quickly than someone with a slower rate.
Hydration and the resulting urine specific gravity can temporarily impact the concentration reading. Drinking large volumes of water dilutes the urine, which lowers the measurable concentration of THC-COOH, potentially pushing the reading below the 150 ng/mL cutoff. This is a temporary effect of dilution, however, not a true acceleration of the underlying metabolic clearance process. Laboratories monitor urine specific gravity and creatinine levels to detect overly dilute samples.
Typical Timelines to Clear the 150 ng/mL Threshold
For a single or first-time user, the concentration of THC-COOH often does not reach the 150 ng/mL level, and clearance is fast. If the concentration briefly peaks near this level, it will drop below 150 ng/mL within 1 to 3 days following exposure. This rapid clearance reflects the minimal saturation of fat tissue and the body’s ability to quickly process the small initial dose.
Individuals who use cannabis intermittently, such as once or twice a week, will experience a moderate clearance time. For this pattern, the concentration is likely to fall below the 150 ng/mL threshold within 4 to 7 days after the last use. This slightly longer time window is due to minor buildup, but the body has enough time between uses to prevent significant accumulation.
For chronic or daily heavy users, initial concentrations can be high, sometimes exceeding 300 ng/mL. In these cases, the body’s fat stores are saturated, and the slow-release mechanism significantly prolongs the clearance time. It can take anywhere from 10 days to 4 weeks for the concentration to consistently drop below the 150 ng/mL mark.
It is important to note the distinction between the 150 ng/mL threshold and other standard cutoffs. The most common initial screening level is 50 ng/mL, and the confirmatory cutoff used by laboratories is often 15 ng/mL. Dropping below 150 ng/mL is only the first phase of clearance for a heavy user. Reaching the lower 50 ng/mL screening cutoff will take noticeably longer, and clearing the final 15 ng/mL confirmatory threshold requires the most time, often extending the detection window by an additional week or more.