Everything that enters the body goes through the natural biological process of metabolism until it becomes completely consumed by the system. Metabolism is a set of biochemical reactions, transformations and processes that happen within the cells; during the digestion of food, the transport of substances between different cells, the transformation of said substances (build-up or breakdown) into energy to sustain the body and the subsequent elimination of waste materials.

Drugs undergo these same processes the moment they are ingested into the body and are detectable in urine, blood, saliva and hair through drug testing within a certain window of time from ingestion until all traces have been flushed out of the system. This window of time is called the drug detection time.

Detection period – the amount of time after a person consumes a drug that a drug test can still show a positive result. For example, after a person consumes marijuana, a marijuana urine drug test can detect the drug for approximately up to a week afterward and possibly longer – up to a month.

Cutoff level – the minimum amount of a drug that has to be present in a specimen in order for it to be considered positive. For example, the cutoff level for marijuana in a urine specimen for an instant testing kit is 50 ng/mL. If marijuana is present in a sample, but the level is below 50 ng/mL, the test would give a negative drug test result. If marijuana is present and the level is above 50 ng/mL, the test would show a positive drug test result.

Factors That Affect Drug Detection Time

Age – The body’s metabolism slows down with age so older drug users tend to retain substances longer in their system.

Body fat – Some drug metabolites like PCP and THC get stored in fat cells, and a person’s metabolic rate tend to go slower the more body fat a person has. It is, therefore, harder to flush out drugs from the system of a user with plenty of body fat.

Ingestion/administration method – The manner by which drugs are ingested has a bearing on their detection times. For example, the body takes longer to flush out orally ingested marijuana, compared to when it is smoked.