Once drugs are introduced into the body, the body will do its best to eliminate all unnecessary and toxic substances.  Drugs whether prescribed or illicit enters your system, does it havoc or benefits then it's byproducts are released out of the system through the urine (among other modes or excretion).  In most cases, it is these byproducts that are measured to determine any presence or recent drug use.  The question now is how long do drugs stay in your urine to generate a reliable drug testing result? Of course this article is written to help shed light on the subject and is not intended to evade the law or promote the use of illicit drugs. 

Factors affecting retention in your system

There are numerous drugs and drug screening methods.  One of the most widely used methods is the urine sample test.  Here, presence of drugs and/or its byproducts are tested.  However, its effectiveness is limited by the time the drugs are in the system. 

There are many factors that determine how long do drugs stay in your urine.  Some of the common factors that affect the test include frequency of use.  The more often the person uses the drugs, the easier it is detected.  Also, the metabolic rate of the person affects the results.  The slower the metabolic process the longer the detection window for the urine test.  Body mass is also a factor to consider with the urine testing.  Higher body fat content can increase the detection window.  Other biological and physical traits associated with slowing down of metabolism like age, health conditions etc affect the time drugs are detected in the urine.  Urine pH also has a significant effect as high acid content results in shorter drug detection window.  Suffice to say, understanding how long drugs stay in your urine entails knowing the metabolic rate of the subject among other factors. 

Different drugs different times

Different substances remain in the body at different rates.  As such, when asked how long do drugs stay in your urine, the obvious question back is what substance are you looking for?

Alcohol for example stays in the system and can be detected within 24 hours or even less.  Amphetamines stay in the system anywhere from 1 to 4 days.  Barbiturates on the other hand can be detected within 1-3 days if they are short acting but can stay as long as 3 weeks for long acting like barbital and phenobarbital.  For cocaine users, the window of detection is from 1 to 5 days.  Marijuana can range from anywhere from 1-7 days to 4 weeks depending on the type used.  Just for curiosity's sake, nicotine stays up to 3 days in the system. 

Drug testing using markers in the urine is just one among many methods of screening.  There are commercially available tests that can be bought and used.  But for more precise screening, it is always best to ask for professional assistance.