The cannabis plant contains more than 400 chemical substances. About 60 of them are unique and are not found in any other plant. These substances are called cannabinoids. The substance that is most responsible for the physical and psychic effects of cannabis is THC, the abbreviation for delta-9-hydrocannabinol. Nowdays it is also possible to make this substance in a laboratory. The concentration of THC in different cannabis products can vary a lot. Marijuana (weed) contains the least concentration of THC. Hashish contains higher concentrations of THC, but it depends on the composition. THC reaches the brain fastest when smoked.
How long does Cannabis (Pot, Marijuana, Hash) stay in the body
To release THC from cannabis it should be heated, often by smoking it. The body absorbs 10-25% of the THC when it is inhaled and only 6% when it is eaten. The dose of THC someone needs to feel high is about 10 milligrams, a quantity of which only a small part eventually reaches the brain. A week after smoking cannabis only 60-70% of the THC has left the body because it is stored in the body fat. It takes about 4-6 weeks before THC is undetectable in the blood. On the other hand, the psychoactive effects are gone after a couple of hours. THC or decomposition products can be detected in urine for a couple of days after the last use. In the urine of chronic users it can even be detected for a couple of weeks after the last use.
In the hair, THC can be detected for as long as the longest hair has been growing. Plus a few days more.