How much marijuana does it take to fail a urine test?

The average drug test will detect from 25 ng/ml(nanograms per milliliter) to 50ng/ml, but some can detect as low as 5 ng/ml, depending on how much the drug test cost and what kind of technology they have. One-three inhalations is equal to about 50 ng/ml.

You're best bet is to avoid smoking at all because it's illegal, unhealthy, and restrains you from doing things with your life. You'll be much more successful in life without marijuana, plus you're memory will remain at its naturally sharp state.