How long does marijuana, weed, pot (THC) stay in your system?
Got a drug test coming up? Will THC be present in the body? We review the basic pharmacology of how marijuana stays in the system, and when you should be worried about potential marijuana addiction, or not.
What is THC?
Tetrahydrocannabinol (THC) is a chemical experts think causes the psychoactive effects of cannabis. THC is found in products that contain cannabis such as:
- Dronabinol (synthetic THC)
- hash (resin from the hemp plant cannabis sativa)
- hashish oil
- marijuana buds
- marijuana flowers
- marijuana leaves
THC works by binding to cannabinoid receptors in the brain and causes physiological, psycho-motor and cognitive effects. In other words, THC is the chemical that gets you high. But there are other reasons why do people use marijuana?
When does THC peak in the bloodstream?
Peak levels of THC depend on how it enters the body. Although marijuana is usually smoked, marijuana can also be eaten. Marijuana is very infrequently injected intravenously. When cannabis is ingested by mouth, THC levels peak after 1 to 6 hours. When inhaled, cannabinoids such as THC are rapidly absorbed into the bloodstream with a peak concentration in 2 to 10 minutes. On average, the effects of marijuana last 3 – 4 hours.
What is the half life of THC?
The half life of a drug is the amount of time it takes for measured amounts in the bloodstream or urine to decrease by half. The half life for THC is long, because THC is stored in the body’s fat cells (THC is highly lipid and not easily dissolved in water). Therefore, the blood plasma and urinary half-life of THC are best estimated at 3 – 4 days after ingestion. But depending on the quantity of THC ingested and frequency of use, half life may even extend to 10-12 days after ingestion.
THC levels and habitual use
People who smoke once per week will increase the level of THC in their bodies over time because THC has never been fully eliminated. For these people, the baseline THC levels rise based on metabolism and fat content in the body. Furthermore, people who smoke or eat marijuana 3-5 times a week, have both higher baseline levels of THC in their systems and longer half lives of THC. In other words, regular users of marijuana are continually drug effected. So regular users of marijuana must realize that THC is generally more detectable in their systems than in the bodies of periodic/episodic users of marijuana.
Drug testing for THC and marijuana
Marijuana can be detected in urine, blood and saliva using methods such as:
- enzyme immunoassay
- gas chromatography
- high pressure liquid chromatography
- radio immunoassay
- thin layer chromatography
THC concentrations in the blood of occasional marijuana users quickly fall below limits of drug testing within 8 to 12 hours of use. However, most drug tests for marijuana compounds are made through urinalysis. And urinalysis for THC is highly precise, and measured in nanograms (n-9), or one billionth of a gram. So in this way, THC can be detected in urine several weeks or months after initial administration with precision. Positive urine based marijuana test results generally indicate use within 1-3 days; however, the detection window could be significantly longer following heavy, chronic, use. So in general, the amount of time marijuana/THC can be detected depends on quantity, potency, duration and frequency of ingestion, and the method used to detect THC or its metabolites.
Am I addicted to marijuana/THC?
Tolerance to the marijuana develops after time and regular use (3-5 times per week). You will know if you are addicted to marijuana if you experience withdrawal symptoms when use is terminated abruptly (physiological addiction) and if you begin to crave marijuana (psychological addiction). There is help for people who are addicted to marijuana, but it is only useful when you are ready to stop. Treatment generally includes some form of psychotherapy combined with support groups. However, there are also alternatives to inpatient drug treatment centers. Please leave your questions and comments here. We’ll be happy to help.
Reference sources: National Cancer Institute info on Cannabis and Cannaboids
Neuroscience for kids: marijuana
National Highway Traffic Safety Administration info on Cannabis
Washington State University Effects of Marijuana
Pharmacology of marijuana
Photo credit: themadpothead