Urinalysis is commonly used for workplace drug testing, it looks for the parent drug and/or metabolite in the persons urine, in this case it’s detecting carboxy-THC.  But, you must remember when it comes to detecting marijuana, THC is stored in the fat cells, taking longer to leave the body than many other substances. Using the urinalysis method means that we can confidently say a person has consumed or been exposed to a substance within a period of time, but cannot determine any impairment.

Two common types of drug testing available:

Pre-screening – with lab confirmation on a non-negative sample

  • A sample is collected, and it is tested immediately for the parent drug and/or metabolite in the sample by qualified technicians.
  • Results in minutes
  • If the technician gets a non-negative result the sample will be sent to the lab for confirmation.
  • Lab will confirm within 24-36 hours.


  • Sample is collected and sent straight to a lab for testing
  • Results will be available 24-36 hours later.

Cannabinoids (THC, Marijuana) Approximate* Detection Time: 1 time only 5-8 days 2-4x per month 11-18 days 2-4x per week 23-35 days 5-6x per week 33-48 days Daily 49-63 days *Some variances in detection range can occur depending on certain characteristics of the individual being testing. These detection ranges are provided as a general guideline, but should not be considered as a concrete time frame.


  • This is a recognized DOT standardized method for drug testing
  • Lab can identify the exact substance being detected.
  • Pre-screening saves time (compared to lab-based), since only positive sample are sent to the lab.
  • Straight to the lab testing prevents any discrepancies between the tester and technician.


  • Need a suitable private location to collect the sample
  • Shows long history for THC use (over 30 days in some cases) without determining the time-period when the drug was consumed
  • Adulteration/tampering of urine is possible
  • It may not be that donor’s urine
  • More costly and time-consuming than other methods
  • Straight to the lab testing is time-consuming

Reasons why urine tests fail us:

  • Because they test for carboxy-THC, we can determine a time-period when the drug was consumed, but not any level of impairment.
  • Pre-screening does not test for active THC.
  • Adulteration/tampering of urine is possible.
  • May not be that donor’s urine.
  • Need a closed room/area to conduct tests.
  • Cannot detect level of impairment.
- SDI Team