What Is THC on a Drug Test?

Testing for THC may be performed:

• If you show signs of drug abuse
• To monitor drug abuse treatment and to quickly note any signs of relapse
  • Regular testing can often help people recover from drug abuse more successfully
• As a requirement before being hired for a job

A positive test result can indicate there was recent and past marijuana use. A urine marijuana test will be positive if the amount of THC in the sample is more than 50 nanograms per milliliter (ng/mL). If a test is negative but a person used marijuana recently, THC levels may be below this level. 

If a urine screening test is positive, a confirmation test can be done by a more sensitive method to ensure the original test result is a true result. 

THC can stay in a person’s system even after marijuana use has stopped, and urine tests can't show the exact day or hour marijuana was last used. The amount of time THC stays in a person’s system depends on a number of factors, such as: 

• How often it’s used
• Length of time since the last use
• Level of THC in the marijuana
• A person’s metabolism and how quickly they process THC
• A person’s level of hydration 

Several different types of tests are used to detect the presence of marijuana. THC, the active component, can be detected in: 

• Urine (the most common type of test used) 
  • One to three days for infrequent users (less than twice/week)
  • One to three weeks for moderate users (several times/week)
  • One month or more for heavy users
  • One to five days for people who eat marijuana, such as in edibles
• Hair: for up to 90 days 
• Saliva: for up to 48 hours 
• Blood: for up to 36 hours

When a person smokes marijuana, the THC (tetrahydrocannabinol) passes through the lungs into the bloodstream, where it is transported to the brain and other organs. THC interacts with what is called the endocannabinoid system, which consists of natural cannabis-like lipid-based neurotransmitters produced by the human body, where the THC can impact parts of the brain that affect sensations, movement, coordination, memory, reward, and judgment.

The effects of weed are felt right away when it’s smoked, and the sensations typically last for one to three hours. If eaten, such as in edibles, the THC may not take affect for 30 minutes to an hour, but the effects can last for several hours.

Side effects of marijuana use may include

• Altered senses
• Distorted sense of time
• Decreased coordination
• Difficulty thinking clearly or problem solving
• Memory problems
• Mood swings
• Fear
• Paranoia
• Anxiety
• Hallucinations
• Delusions
• Increased appetite