Drug Detection Periods:
Urine and Plasma Half-Life

Dr. Joseph E. Graas, Scientific Director
Dr. Edward Moore, Medical Director

A drug’s “window of detection” is the time after which a drug has been consumed by a patient that the drug and/or its metabolites will remain in the patient’s system and be detected in a specimen produced by the patient.  While a drug screen detects the presence of drugs in a patient (what) and a confirmation test reveals the specific drugs that are present and at what values (which and how much), knowing each drug’s detection period is a very useful tool as it can help answer the question when – “When did the patient consume these drugs?”

The below chart shows the most common drugs of abuse and their detection times in both urine and blood samples.  The Detection Period column reveals the detection times for each drug as screened in a urine sample.  While the ranges can be both broad (up to 30 days) and very small (25 minutes or less), they can be used as a guideline to determine new, casual or chronic use patterns.  The Plasma Half-Life is the time after consumption that it takes for the original drug concentration to decrease by half and is measured via a patient’s blood sample.  A shorter half-life means the drug is eliminated from the body faster.  Referring to the chart, the plasma Hydrocodone concentration in a patient will decrease by half every four hours – a very fast rate.  If Hydrocodone is confirmed in a patient’s plasma sample, it is due to either recent use or a very large quantity of the drug was consumed.

It is important to note that detection periods vary; rates of metabolism and excretion are different for each drug and each user.  The periods in the chart should be viewed as estimates only as cases can always be found to contradict these approximations.