it's impossible to answer your question because the answer is different for every single substance. what you're really asking is "how long does it take the body to metabolize (break down and eliminate) various legal and illegal drugs"? the prescribing information for legal medications includes the drug's "half-life. " the half-life is the length of time it takes the body to metabolize half the active ingredient. thus if the half-life of a drug is 12 hours it means half of the active ingredient will still be circulating in your blood 12 hours after you take the medication. that gives you some idea of how long it takes the body to metabolize that particular drug. however we're not talking about a perfectly curved graph when it comes to drug metabolism. you should not assume if a drug has a 12-hour half life that all of it will be eliminated from your system in 24 hours. it might be. or maybe it will all be eliminated at the 18 hour mark. pharmacokinetics is a precise science. in terms of illegal drugs think of it this way: if you take no illegal drugs they will stay in your system for exactly zero hours for drug testing purposes. in other words if you avoid taking illegal drugs you need not worry about drug testing. anyway you shouldn't be taking illegal drugs. (i'm excluding marijuana from this category simply because some states have now legalized it. my exclusion of marijuana does not imply i endorse or approve of using it. ) there are a whole host of problems that go along with taking illegal drugs -- one of which is you don't really know what you're taking. there's no safe "dosing" level. they interact very badly with prescription medications. the list goes on. best bet: if you know you're going to be subjected to random or routine drug tests make sure you have a valid prescription for any medication that might turn up positive and avoid taking illegal drugs. wishing you well!
how long do various legal and illegal drugs stay in your system for drug testing purposes?