If you are enlisting to show up for a drug test and if you are overly concerned despite quitting your fears are indeed reasonable. The probable reason can be the cutoff level.
If your system has washed out the drugs it might not show up even if it is a little below the prescribed cut off level for the drug in question.
A positive test is indicative of the fact that the drug in question is present above the required cut off level. This cut off level is ideally suggestive of abusive behavior. This is because the strips designed to identify abuse with regents and qualitative tests focused to catch up with issue some abuse levels.
Illicit drug use cut off levels are different from prescription abuse levels and they are not same for all drugs. They are, specifically designed, having in mind the cutoff period, the half-life and other metabolic attributes of the drug in question.
It is not enough to test someone just ones. Perhaps the ranges are not within the cut off levels. You cannot for sure say that someone is sober with just one test. Therefore, you need to test the person in question for more than once at different intervals. Continual negative results of the same person’s sample are indicative of sobriety.
If you see that, one of your employee, is not good like before at work, you have every reason to request a drug test to ensure stability. Even if they do not show up to be positive in one test you can test them at different intervals to ensure results; sometimes lag in work can be due to personal issues in life. Either way before you can decide for sure you need to analyze.