Although it is possible to detect various kinds of cannabinoids, it is THC and its metabolites that are most often tested for. THC metabolizes into 11-OH-THC (11-hydroxy-delta-9-tetrahydrocannabinol) and THCCOOH (11-nor-9-carboxy-delta-9-tetrahydrocannabinol) metabolites in the liver. Cannabinoid metabolites are filtered through the kidneys and excreted mostly via urine.
There are three main factors that determine how long cannabinoids stay in the human body. These are:
1. How much is used (dosage).
2. The ingestion method used (mode of ingestion).
3. Regularity of use (frequency).
Age, weight, individual metabolism, levels of physical exertion and genetics also play a part in how long cannabinoids stay in the system.
As cannabis metabolites are fat-soluble, they bind to fat molecules in the body. This means that cannabinoids stay in the body for quite some time. For heavy users who ingest cannabis multiple times a day, it is possible for THC metabolites to be detected for up to 90 days, usually in the hair and urine.
Here’s a rough breakdown of how long THC and its metabolites can stay in the body for.
THC and its metabolites are detectable in the blood almost immediately after ingestion or inhalation. For those who have been using large amounts of cannabis regularly, THC metabolites are detectable in the blood for up to one month after last use.
Saliva testing is the most common method for roadside testing. For occasional users, cannabinoids are detectable in the saliva for between 1 and 3 days. For heavy users, it is possible to detect THC metabolites for up to 1 month after last use.
Urine testing is one of the most common ways of testing for cannabis. Cannabinoid metabolites are detectable in the urine for the following amounts of time after last use:
- Rare or infrequent users (once a week or less): around 1-3 days.
- Occasional users (around three times a week): 3 to 7 days
- Moderate users (four times a week): 5 to 10 days
- Chronic users (daily): 10 to 30 days
- Chronic heavy users (multiple times a day): 30 days +
The urine marijuana test will test positive if the amount of THC in the sample is more than 50 nanograms per milliliter (ng/ml). This is called the cut-off level.
Hair Follicle Testing
Hair testing is the most sensitive, and can detect THC metabolites for up to 3 months after last use. Trace amounts of THC’s metabolites can remain in the hair for quite some time. Usually, a 1.5 inch hair segment is asked for in order to provide a window of use over the last three months.
Whilst hair follicle tests can provide some information about a person’s cannabis use, they are not always accurate, and the tests often produce false negatives. Hair samples are also prone to contamination, making it difficult to detect with high degrees of accuracy. Hair follicle testing is this usually used in tandem with urine testing.
Is it possible to detect CBD?
Most drug tests searching for cannabis are calibrated to detect THC and its metabolites. Whilst it is certainly possible to test for CBD and other cannabinoid metabolites, it is not really common to do so. CBD also has little psychoactive effect, so it is unlikely that CBD is going to be tested for.
Where CBD may produce a positive result for cannabis use is when products with high concentrations of CBD are used regularly. In such instances, it is not the CBD that is being detected, but the building up of trace amounts of THC over time. THC has a tendency to accumulate, even when used in almost miniscule amounts.
There are also some hemp-derived CBD products that have tested above the 0.3% THC limit, so it is also possible to ingest a CBD product that contains higher levels of THC without realizing it (i.e. it produces almost no psychoactive effect, but ends up being detected and pushes you pass the 50 ng/ml THC metabolite threshold.
Is it possible to flush out cannabinoids from the body?
As cannabinoids are lipophilic, it is difficult to get clear the body of their metabolites. Exercise, a healthy diet, plenty of green tea & water, and herbal & vitamin supplements could potentially help rid the body of cannabinoids and their metabolites, but it will still likely take around 1-2 months to get below the threshold for most people.
Regular exercise, stopping cannabis use and plenty of hydration is the ideal flushing method for chronic cannabis consumers. Some also stop exercising 1-2 days before any test in order to prevent a spike in any THC metabolites being left over in the body’s fat.
Sadly, as cannabis is federally illegal, there are many jobs that prohibit its use, even in states with a medical marijuana program. Although there are some protections for medical cannabis patients in some states (i.e. off-duty use for medical purposes is fine), there are other states where such protections are not in place. This means that an employer does not necessarily have to accommodate your medical cannabis use.