How Long Does Cannabis Stay in Your System?

Despite a surge in cannabis research, there is still no universal method to telling if someone is 'high.'

Even with all of the scientific research being conducted in states with now-legal cannabis, there is still not a universally agreed-upon method to determining how long cannabis stays in your system, or can be detected on a drug test. This is because, like many pathways in the human body – and more specifically the blood brain barrier (BBB) – the amount of concentration depends on a laundry list of factors. Frequency, amount, and constituent concentration (how much CBD vs. THC from a given plant) can all greatly affect the rate of cannabis concentration in vivo.

What’s the problem?

Testing for specific cannabis concentration is tricky because marijuana constituents such as THC are what’s known as “fat soluble”. In other words, marijuana is broken down into constituents that are then sent to the BBB via the liver. This is the same process your body uses to break down alcohol into individual constituents, the difference being that cannabis constituents are stored in fat rather than the blood stream or remaining in the liver like alcohol. This makes cannabis concentration difficult to test. Obviously, fat cells are everywhere in the body. So once the cannabis constituents get into the blood stream, they can then be stored anywhere in the body that contains fat cells.

how long cannabis stays in your system
Alcohol is water soluble, cannabis is fat soluble. This makes marijuana difficult to test via urinalysis.

Alcohol, comparatively, is water soluble. Because of this, once broken down, alcohol constituents are equally distributed about your blood, which is mostly water. Water soluble molecules also metabolize at a constant rate, fat soluble molecules do not. This is the main problem with attempting to test THC concentration in someone’s blood, it may be there but it’s not telling the entire metabolic story, like alcohol does.

Furthermore, most urine drug tests, or urinalyses, test for one of two cannabinoid compounds occurring in cannabis. The first, THC, you’re most likely familiar with. The second cannabinoid is a metabolized version of THC known as THC-COOH, shown below.

how long cannabis stays in your system

THC is metabolized in the liver into THC-COOH and other chemical constituents. THC-A does not stay in your system long, but that doesn’t mean you’ll pass that drug test. Previous studies on the pharmacokinetic effects of marijuana consumption have shown concentrations of metabolized THC-COOH lasting far longer in the blood stream than THC or other THC-constituents.

how long cannabis stays in your system
THC-COOH concentrations last far longer than other THC constituent molecules. Photo: Chem Biodivers

This doesn’t mean that particular individual is ‘high.’ They may not have even consumed cannabis that day. THC-COOH concentrations in rare users can be detected on a urinalysis up to 48 hours after ingestion, on average.

THC-COOH concentrations in frequent users can be detected for far longer, up to 30 days after ingestion on average. One extreme case took over 2 months (67 days) before the THC-COOH concentration in their system was no longer detected via urinalysis. The more frequent a user uses cannabis, the greater the concentration of THC and THC-COOH in the body. If use is so frequent that the body cannot rid itself of the remaining THC-COOH molecules, i.e. multiple uses before the average 48-hour detection period, they begin to pile up. Unable to bind the cannabinoid receptors in the brain (which is how users feel ‘high’), the excess THC-COOH simply circles around the blood stream. Sometimes they may find an accepting fat cell for storage, but the more frequent the use, the more bound the receptors become. This leads to a higher concentration of unbound THC-COOH in the blood, which, in turn, extends the THC-COOH urinalysis detection window.

There are a litany of factors that play into how high a person is, or feels. These factors mentioned previously are only a few of the factors. Others include weight, percent body fat, and age. It may be somewhat surprising that with all of the studies being conducted on cannabis, not one has yielded a tried-and-true method to explain a person’s cannabis intoxication. With the continued high demand from law enforcement and government agencies, alike however we may just find the magical marijuana concentration equation, yet.