Perhaps you’re concerned about an upcoming drug test, or maybe you’re just curious about the long-lasting effects of marijuana. Whatever the case, it would be nice if there was one short answer, a certain number of hours or days after consumption that would guarantee any remnants of cannabis have disappeared from your system. However, as you might have guessed, it’s far more complex than that. When trying to determine how long marijuana stays in your system, it’s important to consider age, sex, body type, metabolism, dosage, frequency, strains, and much more, as all of these are relevant factors in trying to make the closest and most accurate estimate.
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What Does the Timeline Look Like?
After smoking, you can usually feel the effects of weed in under half an hour, with varying rates for other methods of consumption. Feeling high – a sense of relaxation, feeling talkative or giggly, having altered sensory perception, sleepiness, dry mouth, increased appetite, etc. – can last for any number of hours, again depending on many factors. Typically, short-term effects take between three and six hours to wear off.
Long term, small amounts of chemicals may remain detectable for days, weeks, even months after use. The higher the frequency and amount of cannabis you consume, the longer the chemicals can stay in your body. It’s not the marijuana plant itself that remains detectable, but rather the THC metabolites that may be stored in various parts of the body.
The amount of time it takes for half of a drug to leave your system is called the "half-life." According to Vermont Health Commissioner Mark Levine in Burlington Free Press, the half-life of THC is about 36 hours for an occasional user. This means that within 36 hours of consumption, half of the THC will have left the body. It generally takes about five half-lives to be under detectable levels.
Drug Testing
There are many ways to measure and detect the amount of marijuana in the body.
The most common form of drug testing is urine testing. If testing urine, cannabis metabolites may appear for three days after using for occasional users, seven days for moderate users, 15 days for chronic users, and more than 30 days for chronic heavy users, according to Mayo Clinic Proceedings. False positives are uncommon due to the technology of tests that exist, including immunoassay tests and gas chromatograph mass spectrometer tests.
Blood tests, though occasionally used in suspected DUI cases and roadside accidents, are not reliable, as even those still feeling the effects of a high from marijuana may test negative for cannabis, based on the way the body processes it. A blood test has a very narrow window of time to properly detect the drug, as it does not measure the same THC metabolites that stick around and can be found with other tests.
Saliva tests are similar to blood tests in their small time-frame of efficacy, but they may also be used to determine cannabis use. For occasional users, there may be remnants up to three days after use, while there may be evidence in chronic users for up to 29 days after use.
Drugs stay the longest in hair. Using a hair follicle test, marijuana can be detected up to 90 days after use. Because of the pace at which hair grows and the way that marijuana can pass through blood vessels, it can take months for trace amounts to fade.
What About CBD?
CBD is cannabidiol, another substance in marijuana. It has different effects and operates differently in the system compared to things like THC. Because most drug tests, especially the most standard urine tests you are likely to encounter at a job or similar circumstance, only measure THC metabolites, CBD is highly unlikely to cause a test to come back positive. Those who take CBD or hemp oil are likely to pass cleanly. If the dosage is high enough, it has the potential to trigger a false positive, but a consequential test would probably not yield the same results.
What About Synthetic Marijuana?
There is not a great amount of data available on synthetic marijuana. It’s often used by those who have an impending drug test but feel unwilling to give up the drug. These alternatives to normal marijuana are often called "spice" or "K2," and while they may show up less easily on a test, they remain quite dangerous and unpredictable in their side effects and potential of overdoses.
There are two chemicals, JWH-073 and JWH-018, that are detectable in the system. It takes about seven hours and two hours, respectively, for those to leave the body completely. Urine tests may detect synthetics for about three hours, blood tests for about two days, saliva up to 12 hours, and any longer amount of time for a hair test.
How Can I Get Weed Out of My System Faster?
If you’re wondering whether or not it’s possible to fool a drug test, the answer is probably no. While many speculative strategies have emerged over the years, most are just urban legends. Some suggest drinking a lot of liquids and then using a supplemental B-12 vitamin, but this will only dilute the THC that is still present. Aside from that, most strategies involve trying to tamper with samples or cheating the process, both of which are unwise and easily noticeable. Obviously, adding things like salt or bleach can be detected with no trouble, and testing agencies often screen specifically for chemicals like pyridinium chlorochromate that are meant to eliminate the THC metabolites.
The best method for ensuring a negative drug test is to abstain from use altogether. Most people may not know that even secondhand smoke exposure can trigger a urine test to come back positive, especially if you’re around the drug in a poorly ventilated room for a long period of time. 
If you don’t have enough time or can’t get yourself to abstain from marijuana, there are options to try. Green Gone sells THC detox kits that help your body metabolize faster. Their products are vegan and made in the U.S, and they even come with test strips so you can test yourself.
Again, there is no guideline set in stone to determine at what point there is no longer marijuana in a person's body. Estimations can be made depending on the type of drug test being used, but each individual is different. Chronic smokers and beginners will have very different experiences, and the same goes for teenagers versus adults, men versus women, healthy people versus ill people, and so on. The countless types of marijuana and the forms in which it may be consumed also play key roles in answering the question: How long does marijuana stay in my system? The most important thing is to be cautious of what you put in your body and when, particularly if you have the possibility of random drug tests or a specific deadline approaching.
