How long does cannabis stay in the body?
Answer - nick
It is my understanding that, unlike @MisterBlaack states, hair is a rather unreliable way to test for cannabis. The reason being is THC is fat soluble, our hair is protein. Hair is a great way to test for substances that leave our bodies quickly, i.e. cocaine.
While it is possible for THC to show up in hair, it's a rather unreliable form of testing. Urine samples is the most reliable form of testing for THC.
THC is stored in our fat cells, so like @MisterBlaack states, it will vary depending on your exercise and metabolism. Another important factor to not overlook is the amount of cannabis or THC consumed.
You can generally expect cannabis/THC to be undetectable in your body 4-5 weeks after use.
Answer - misterblaack
It really depends on weight, exercise level, and most importantly type of test being taken. THC will stay in your hair longer than urine, for example.