How long does marijuana stay in the body?

While marijuana itself does not actually stay in the body, some of the chemicals in the drug do. THC (delta-9-tetrahydrocannabinol), the substance in pot that's mainly responsible for people's high, may stay in the body forever — scientists aren't exactly sure. However, THC is only detectable for a certain period of time after using marijuana or being exposed to marijuana smoke.

Compared to other controlled substances, THC is able to stay in a person's system for a relatively long period of time because it is fat-soluble. Being fat-soluble allows it to be stored in fatty tissues of various organs. From here, THC is slowly released and metabolized. This metabolite of THC is then excreted and cleared from a person's system.

In testing to see if someone has recently used pot, there are two important substances to keep in mind: THC and 9-carboxy-THC. 9-carboxy-THC is a product of the body's metabolism of THC and, more importantly, it is detectable for a longer period of time than THC is detectable. This is the reason that drug tests, namely urine tests, look for 9-carboxy-THC.

Many of the following numbers are estimates. The actual amount of time that these substances are detectable in a person's body depends on several factors, including how much pot is used, how often a person uses it, and the rate of his/her metabolism of the substance.

	Blood Tests		Urine Tests
	THC	9-carboxy-THC	9-carboxy-THC
Frequent Users*	4 - 8 hours	2 or more weeks	2 weeks – 1 month†
Infrequent Users**	3 - 4 hours	2 - 3 days	Up to 10 days

^‡ Some private companies may use hair tests to detect possible marijuana use. Positive hair test results have been found to be unreliable.

* Frequent users are defined as people who use marijuana several times per week, if not more often.

** Infrequent users are those who use marijuana seldom enough that THC and/or its metabolite are no longer detectable before their next use. In essence, these users do not use pot often enough to allow for the tested substances to build-up from one use to another.

^† The detection period for 9-carboxy-THC in urine can be as long as 3 months in extremely heavy users.

On a final note, it's interesting that this question is brought up since these types of questions typically arise from some specific concern. People usually ask this question when they are worried about being tested by an employer. If this is the case, then maybe it is time to carefully weigh marijuana use against: (1) the consequences of being suspended or losing a job, and (2) the health risks associated with using marijuana.

You can read the Related Q&As below on drug testing.

Alice

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