There is no way to state with complete accuracy how long marijuana will stay in your system after ingestion. The reason for this lack of scientific certainty is due to several different factors, most of which have to do with the specific person ingesting it. Some of the factors to consider when asking how long marijuana stay in your system depend on a wide array of variables ranging from the method of intake, a person’s weight, a person’s body mass index, a person’s metabolic rate, the amount of the substance used, the frequency of use, and finally the potency of the particular strain of cannabis used. This article will attempt to explain the entire process that occurs when marijuana is introduced into your body, and how it is ultimately broken down and purged from your system. Even though there are relatively few studies conducted and published from the scientific community on this subject, we at least know some basic information that has been gathered from a variety of sources.

Marijuana is similar to all substances that enter the body in the regard that they all must be digested, broken down, separated, and then delivered to the appropriate place within the body for processing and finally, removal. Marijuana is most commonly ingested by smoking it, though there are other ways to introduce it into your system. Once it enters your system, your body begins to break it down through the metabolism process. Metabolism is the series of processes that occur in our bodies by which food and other substances are converted into the energy and products needed to sustain life. The chemical found in marijuana is called THC or Tetrahydrocannabinol. THC is primarily metabolized by the liver and then excreted through our kidneys and then out of our system in our feces and urine. The remaining THC metabolites that do not easily pass through our body’s excretion process ultimately end up stored in our bodies fat cells. THC isn’t water soluble, which is another way of saying that THC doesn’t dissolve in water. This is significant because THC isn’t broken down easily or quickly by the abundance of water that exists in our bodies, so it remains in our bodies fat cells much longer than other drug metabolites that are water soluble. A person’s body mass index or more commonly, their body fat percentage, is a major factor to consider when figuring out how long marijuana stays in our system. The more fat a person has in them directly correlates into how many metabolites reside in our body, and hence, how long the evidence of marijuana use will continue to show up in our urine. So to be clear, people that carry a higher percentage of body fat will continue to excrete evidence of marijuana usage for longer than someone who is relatively skinny with a low percentage of body fat.

The frequency of marijuana use and the potency of the particular marijuana used are the next major factors to consider when calculating how long marijuana stays in our system. A person who uses marijuana on a daily basis is going to have more metabolites stored in whatever percentage of body fat that they have, as opposed to someone that uses marijuana less frequently than every day. Since the body is always removing these metabolites through the metabolism process, someone that is constantly reinforcing the amount of THC metabolites stored and removed from their fat fells is going to show signs of marijuana usage for longer than the casual user. The potency of the marijuana is also an important factor to consider when determining how long marijuana stays in our body. The marijuana currently found in the United States has a THC concentration of around 8.5%, which is significantly higher than the 3.5% back in 1990. It has been estimated that the marijuana sold in coffee shops throughout Holland has a THC concentration of around 19 percent. Since marijuana comes in so many different strengths, and since these strengths or potency levels are not printed on a label, it is relatively impossible to know exactly what level of THC concentration a person is ingesting when using marijuana. If a casual user were to smoke an incredibly potent strain of marijuana, it would have the same effect on THC content in a person’s fat, as if a chronic or daily user were to smoke a less potent strain of marijuana. This is one of the reasons that nobody can accurately predict how long marijuana actually stays in the body.

Now that we have covered the major factors that contribute to how long marijuana stays in our system, we can now extrapolate with a clearer degree of certainty how long the body will continue to show evidence of marijuana usage. It has been suggested that evidence of marijuana usage can be detected by drug testing for up to 30 days in most cases. This time frame is not accurate in many cases. Some people can show evidence of marijuana usage for periods of time far greater than 30 days, in some cases up to 90 days. The graph below shows how long most users can expect to see evidence of marijuana use in their body. The graph presumes a THC concentrate of around 10% in the marijuana ingested by the user.

How long marijuana can be detected in a person’s hair is a much easier proposition to calculate. Human hair is like a record of what we eat, drink, inhale, and even where we live. As mentioned earlier, marijuana metabolites are all eventually excreted through our urine and feces. The presence of metabolites in the hair is based on the same premise. The bloodstream circulates metabolites throughout the body, and since our bloodstream nourishes developing hair follicles, metabolites are deposited in the hair follicle where they become trapped in the hair shaft as it grows out from the follicle. Hair on average grows 1/2 an inch every 30 days. So if your hair is 1.5 inches long then marijuana use is detectable up to 90 days. Marijuana can be detected even longer with long hair.