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Can A Urine Test Reveal Marijuana Use and Degree of Impairment?

In California, the use of marijuana is legal for medical purposes, but that does not mean that anyone is able to use it. Only those with a valid prescription from a medical doctor are able to use the drug. If you are caught using marijuana without a prescription or when getting behind the wheel of a car, you may be brought up on criminal charges.

Urine Tests Are Common, But Flawed

One of the ways that law enforcement will determine if marijuana is present in a suspect is by asking the accused to submit to a urine test. A urine test can detect the presence of marijuana for days, weeks, and even months since the last time the drug was used.

The amount of marijuana detected in the urine is affected by:

  • Kind of urine test used on the suspect
  • Frequency of marijuana usage
  • Dosage of the last time used
  • Suspect's genetic makeup
  • Metabolism
  • Digestive and excretory systems
  • Other, unknown factors

Unlike testing for alcohol, which has a uniform effect on all users, marijuana can affect every individual body differently. Testing assumes marijuana affects everyone the same.

Can a urine test determine how impaired I am?

In addition to urine tests being able to pinpoint the last use of the accused, these tests do not test for the psychoactive ingredient in marijuana, THC. These tests check for the non-psychoactive metabolite THC-COOH which lingers in the body up to 100 days after marijuana use with absolutely no impairing effects. Because urine tests do not detect THC, there is no way that law enforcement can test the level of impairment of someone accused of marijuana use.

According to Quest Diagnostics, half of all drug test positives are for the presence of marijuana, but this does not indicate anything about the user except they consumed some amount of marijuana anytime in the past few months.

If you have questions about marijuana urine testing and how this may affect a criminal charge you are facing, call The Law Office of Christopher P. Welch for a free case consultation.