Clinical Insight – THC Monitoring

Marijuana is the most commonly abused illicit substance in the United States. Because THC can come from a variety of sources and test results may be influenced by multiple factors, this issue of Clinical Insight reviews key concepts to consider.

Detection Times:

• • Oral Fluid: The window for detection of THC is approximately 24-48 hours. Because of this short time frame, these results can help determine if recent use has occurred but cannot be used to monitor elimination in a person with a history of chronic use.
  • Urine: The detection window depends on the individual’s history of use:
    • Occasional Use: Up to 5 days when smoked and approximately 9 days after an edible product.
    • Chronic Use: Because THC accumulates in the fatty tissues of the body with chronic marijuana use, it can be detected for up to 30 days or more after THC use is stopped.

Drug Levels:

• Creatinine Adjusted Values (CAV):
  • The CAV is a clinical tool to assist clinicians to compare drug levels in urine samples with different concentrations, which are reflected by the creatinine. This is important because drug levels in urine are directly impacted by the creatinine, which can misleadingly appear to increase or decrease THC levels.
    • The higher the creatinine, the more concentrated the urine. This results in higher detected drug levels and may create the false appearance of continued or new use of a drug.
    • The lower the creatinine, the less concentrated the urine. This results in lower detected drug levels, which may falsely appear like abstinence of drug use.
• Utilizing the CAV enables comparison of multiple samples from an individual over time while minimizing the impact of fluctuating creatinine levels.

THC Sources:

• • Marijuana: The traditional plant form, which is commonly smoked or made into edibles. Delta-9-THC is the main component that causes the drugs psychoactive effects. Federally, marijuana is a Schedule-1 Controlled Substance but may be deemed legal recreationally depending upon individual state laws.
  • Medical Marijuana: A medical marijuana card is issued by a physician which permits the use of marijuana for the use of certain medical conditions. 
  • CBD: CBD is sourced from either the hemp plant or the marijuana plant. It can contain Delta-9-THC as an impurity. Federal guidelines allow up to 0.3% THC in hemp derived products, but due to lack of regulatory oversight on CBD production, this level may be exceeded.
  • Delta–8-THC: This product is a cannabinoid that has become popular in recent years due to its similarity to Delta-9-THC. Delta-8-THC is also present in low concentrations in the cannabis plant.
  • Dronabinol: A synthetic form of Delta-9-THC available by prescription (Marinol®) to treat anorexia and weight loss due to cancer or HIV.
  • Passive Exposure: Individuals in the immediate environment to smokers may be exposed to THC by passive inhalation.  Studies suggest the environmental conditions needed to contribute to a detection in a urine drug test would be limited to small, unventilated areas with a heavy smoke burden. Detections from this type of exposure are generally low and confined to roughly 24 hours after exposure. Recent studies found that passive inhalation did not produce positive results in oral fluid tests.