Edibles, cannabis-infused food products, are a popular way to consume tetrahydrocannabinol (THC), the psychoactive compound in cannabis. As their use increases, many people are concerned about whether these orally ingested products will cause a positive result on a standard drug screening. The short answer is yes, they can, but the detection timeline is influenced by how the body processes edibles compared to other consumption methods. Understanding the science behind cannabis metabolism and drug testing is key to knowing what to expect from these screenings.
How Drug Tests Detect THC Metabolites
Standard drug tests for cannabis do not look for the active compound, delta-9-THC, which causes intoxicating effects. Instead, most screenings detect a specific non-psychoactive byproduct created after the body processes the compound: 11-nor-9-carboxy-delta-9-tetrahydrocannabinol, abbreviated as THC-COOH.
THC-COOH is formed when THC is broken down by the liver and is highly fat-soluble, meaning it is stored in the body’s fat cells. The metabolite is slowly released from fat stores back into the bloodstream and eliminated through urine and feces. This slow elimination process allows THC-COOH to be detected for days or even weeks after the psychoactive effects have worn off.
The presence of this metabolite indicates past exposure but does not necessarily correlate with current impairment. Tests measure the concentration of THC-COOH. The most common cutoff for a positive urine screening is 50 nanograms per milliliter (ng/mL). A more stringent confirmation test, often using gas chromatography-mass spectrometry (GC-MS), may use a lower cutoff of 15 ng/mL.
The Unique Metabolic Pathway of Edibles
Edibles follow a different metabolic pathway than inhaled cannabis, which impacts drug testing. When cannabis is smoked or vaped, delta-9-THC quickly enters the bloodstream through the lungs. Conversely, when edibles are consumed, the THC must first pass through the digestive system before reaching the liver.
In the liver, the compound undergoes “first-pass hepatic metabolism” before entering the circulatory system. During this process, a higher percentage of delta-9-THC is converted into 11-hydroxy-THC, a secondary, highly psychoactive metabolite. This metabolite is more potent than the original THC and causes the intense, delayed effects associated with edibles.
The 11-hydroxy-THC is then quickly metabolized into the long-lasting, fat-soluble THC-COOH, which drug tests screen for. Although oral ingestion results in less total THC reaching the bloodstream compared to inhalation, the higher initial conversion to THC-COOH can contribute to a persistent, detectable level of the metabolite. The full metabolic cascade can establish a longer detection window than a single instance of smoking for some individuals.
Variables Affecting Detection Time
There is no fixed duration for how long THC-COOH remains detectable, as several factors influence the body’s elimination rate.
Frequency of Use
The frequency of cannabis use is a major determinant. A one-time user clears the metabolite much faster than a chronic, heavy user. For a casual user, a positive test with the standard 50 ng/mL cutoff is unlikely after a few days, while daily use can extend the detection window to 30 days or more.
Dosage and Potency
The potency and dosage of the edible consumed also play a direct role. Higher doses lead to a greater concentration of metabolites that take longer to eliminate.
Metabolic Rate
An individual’s metabolic rate affects how quickly the liver processes THC and how rapidly the body excretes the resulting metabolites. Individuals with a faster metabolism tend to clear the compounds more quickly.
Body Fat Percentage
Body fat percentage is a significant variable because THC-COOH is stored in fat tissue. A person with a higher body fat percentage has more storage sites for the fat-soluble metabolite, leading to a slower and more gradual release back into the bloodstream. This slow release can prolong the detection window. Furthermore, a person’s hydration level and overall health status can introduce variability into the final urine concentration of the metabolite.
Comparing Different Drug Test Methods
The specific type of drug test used determines the window of time in which THC metabolites are detectable.
Urine Testing
Urine testing is the most common method for pre-employment and random screenings due to its cost-effectiveness and long detection window. For an infrequent consumer, THC-COOH is generally detectable in urine for up to a week, but chronic users may test positive for a month or longer. The standard cutoff level of 50 ng/mL balances sensitivity with ruling out passive exposure.
Blood Testing
Blood testing offers a much shorter detection window and is typically used to determine recent use or potential impairment, often in post-accident or roadside scenarios. Active delta-9-THC is usually detectable for only a few hours, though the metabolite THC-COOH may be present for up to a few days. Due to its invasive nature and short window, blood testing is not the preferred method for general workplace screening.
Hair Follicle Testing
Hair follicle testing provides the longest history of use, as THC metabolites become incorporated into the hair shaft as it grows. This method can potentially detect cannabis use for up to 90 days. Hair tests typically screen for the presence of the parent drug, THC, rather than the metabolite, measuring historical use.
Saliva Testing
Saliva testing detects the parent THC compound rather than the metabolite. Its detection window is generally limited to the most recent 24 to 72 hours following consumption.