How long can a drug be detected in a person’s urine sample? The detection time depends on several factors, the most important of which are how long the drug was taken and how much was taken. Many drugs are stored in fat, such as marijuana. Longtime users can store enough marijuana to be detected for four weeks in urine, as reported in literature. Heavy users will also be detectable for extended periods; cocaine metabolite can be detected for weeks in heavy crack smokers.
Longtime users can store enough marijuana to be detected for four weeks in urine. Drugs are detectable for the longest period of time in hair, but are affected by dyeing and bleaching. These factors make interpretation more difficult and less reliable. Urine is the specimen with the next longest detection window for drugs. Saliva and blood offer the shortest detection time. Urine has been the “gold standard” specimen for detecting drug use for some time. Urine is a good specimen for detecting use of prescribed drugs, too. General time frames for detecting drugs in urine, after prescribed or casual use, are provided below: