The amount of time weed stays in your system is a pretty complicated topic. There are a ton of variables you have to include and a small mountain of research studies to go through. Also, the time varies based on what’s being tested i.e. urine, blood, hair, or saliva. The chart below is the sum of several weeks spent researching this topic in depth. I hope you’ll continue reading below where I break down all the research.
Table of Contents
There is a ton of information in this article. I hope you’ll read the entire thing, but if you need to know something specific use the links below to skip down the page.
THCCOOH & What It Means For You
Factors That Affect THC Detection Times
How Long Does Weed Stay In Your Urine?
Additional Factors Affecting Urine Tests
If You Only Smoked Once / Took One Hit
Heavy Usage / Extreme Cases
Detection Times For Marijuana In Your Blood
Heavy Use / Extreme Cases
How Long Does THC Remain In Hair Follicles?
How Long Is Weed Detected In Saliva / Mouth Swab?
Heavy Use / Extreme Cases
Most people think of a marijuana drug screening as something that looks for THC. This isn’t quite accurate. The vast majority of screenings are looking for a compound known as THCCOOH. Here’s why:
THC actually lasts for only a few days in your system. So, labs typically turn to another compound found in marijuana, THCCOOH. Unfortunately, this has a much longer detection time than THC.
Note: There are a few tests that look at compounds other than THCCOOH. For example, some blood tests have used both THC and 11-OH-THC.
One of the most important things to remember is everyone does not have the same detection times – not even close. Thus, there is absolutely no way for anyone to positively predict your exact detection time frame. I will do my best to guide you as much as possible, however, you must under the following factors to really understand how detection times work.
- Frequency: How often do you smoke? This idea will be covered more thoroughly throughout this article.
- Dosage: How much do you smoke at a time? Also, how potent is the weed?
- Weight: The more body fat you have, the longer it takes to clear a drug test.
- Exercise: Exercising speeds up the rate of THC detox. Are you are naturally active?
- Metabolism: A fast metabolism with result in shorter detection times
- Liver Health: Much of the THC you smoke is processed through your liver. If you have a liver condition it would cause you to process it more slowly.
- Test Sensitivity / Cutoff Level: Truth is, with most tests you can have a little bit of THC in your system and still pass. Tests have a set amount of THC that will still result in a negative test. Cutoff levels differ depending on what type of test/screening being used.
- Testing Method: Not all tests are created equal so some are more sensitive than others. For example, this study demonstrates how GC/MS (gas chromatography-mass spectrometry), when compared to Immunoassay testing, detects THCCOOH faster and for longer periods of times.
Urine tests are perhaps the most prevalent type of drug testing that you will encounter. One reason is urine tests are much cheaper to perform than the other types of drug screening methods such as hair, saliva, and blood. Unfortunately, urine tests also yield the longest detection times with the exception of hair. The cutoff level for urine is typically 20 or 50 ng/ml, however; this number can vary.
In addition to all the factors just mentioned, there are several factors that apply specifically to urine screenings.
- Fluid Intake: This factor really only affects urine tests. Drinking more water will dilute the amount of THC in your system. Drinking too much water could cause you to fail the test.
- Urine pH: Urine that is more acidic has a shorter detection time.
Okay, let’s get on to some real numbers, shall we? Perhaps the number one factor is how much you smoke. Below each category of usage, you’ll see a range of detection times. You can use some of the factors about to help figure out where you might fall within the range.
This category is for people who only used a small amount. If your one-time smoking was an all out bluntfest or a heavy dab session then you will likely experience longer detection times. Typically, people who smoke once will test positive for marijuana for 2-7 days. Again, depending on how much you smoke, along with the factors mentioned earlier, you could have a longer detection time. These numbers also assume you were completely clean before your one-time smoking.
Okay, let’s talk about the studies these numbers come from.
A study done in 2001 gives us several useful figures for single use. First off, they state urine typically does not test positive right away. The study found it took an average of 4-6 hours after smoking for marijuana to be detected. This number is largely dependent on the type of equipment used. That same study found an average detection time of 42-58 hours. This is roughly 1.8-2.5 days. Remember, these numbers are the average so individuals could be higher or lower.
According to an article published in the International Journal of Clinical and Laboratory Medicine, after smoking one marijuana cigarette, THC is detectable in urine for 2-4 days.
Several websites cite A research paper by NDCI claiming single use is detectable for 5-8 days. These figures, however, are simply an endnote. The endnote references a site that sells products design to help you pass drug tests. The specific reference page does contain the same figures, but no actual source is to be found anywhere on the page. It’s basically the word of people who directly profit from people thinking they’re going to test positive. I’m not saying these numbers are wrong, but I’m just not seeing real proof.
Also, it seems the 5-8 days was taken out of context. If you read the NDCI paper you’ll find the author actually recommends this: “At the 20 ng/mL cutoff for cannabinoids, positive urine drug test results for the single event marijuana use would not be expected to be longer than 7 days.”
An occasional user is someone who consumes cannabis several times per month. Occasional users will typically have a detection time between 7-20 days. Most people will be clean in less than 2 weeks, but as always, exceptional cases are possible.
Truth is, there is not a ton of published research on this group of people. Most of the research focuses on chronics users or one-time users.
If you’re spreading out your smoke sessions then it’s possible you’re getting clean before your next session. If however, you’re smoking about once a week then it’s possible for the THC to build up resulting in a longer detection time.
A regular user is someone who consumes cannabis several times per week. 30 days has been the long-standing “gold standard” for THC detection time in regular users.
This number has come under some scrutiny, however. Some researchers believe the detection time is much less. The NDCI study mentioned earlier, which aims to set detection boundaries for courts, claims it would be unlikely for a regular user to test positive after 21 days. The problem with this number (and the article in general) is it doesn’t discuss all the individual factors such as body fat and exercise.
So, while most people will be clean in 20-30 days, it is possible for regular users to test positive for longer.
A heavy user would be someone who smokes daily (or close to it). Heavy use over a prolonged period of time also increases your detection times. Using heavy concentrates may bring your number up as well. Typically a heavy cannabis user will test positive for 30-60 days, however, much longer times have shown up in published research. Extreme and unusual cases could test positive for 100+ days.
The National Drug Court Institute took a look at 8 different studies. Of these studies, 4 relied on subjects who were self-reported heavy or chronic users. The longest detection time from each study was: 40 days, 67 days, 25 days, and another study also found 25 days to be the maximum time to test positive. Keep in mind these studies were done in the mid to late 80s so they may not be directly comparable to modern cannabis. Also, note many of these studies relied on relatively small sample sizes of participants.
Ellis et. al. found that out of 86 patients, who described themselves as chronic users, the average detection time was 27 days, but could take as long as 77 days.
Now, a quick look at the extreme cases. There are at least 2 documented cases of people testing positive in excess of 90 days. In 1991, a study by Lafolie P. et. al. had a participant who tested positive for 93 days. A year later, another study found a participant who tested positive for 95 days. Both of these studies were conducted in the early 90s when weed was not as potent as it is now. It would not surprise me to find extraordinary cases of people testing positive for 100 days given the high potency of modern cannabis.
Your blood will test positive for THC for a much shorter detection period in blood as compared to urine. THC detection times for blood are typically a week or less, however, extreme cases have tested positive for over a month.
Most one-time users will typically be clean for a blood test in 1-2 days. Some users have shown to test negative only 6 hours after use.
A 1992 study found that participant’s blood tested positive for THC-COOH for 6-27 hours after smoking a single “high-dose” marijuana cigarette. Keep in mind high-dose is referring to marijuana that is 3.55% THC. This number is up to 10 times less potent than modern weed. For this same study, a low dose joint was 1.75% THC. These subjects tested positive for 6-12 hours after smoking. So, you can really see how potency of your weed matters when it comes to detection times.
Another test, using the same potency weed as the previous study, found that test subjects tested below 1 mg/ml. This study only included 6 participants.
If you’re only smoking a few times per month then you should have fairly low detection times. In fact, it’s possible you are getting completely clean between usage if you’re spacing them out. Expect to test positive for 1-3 days after occasional use.
NORML (National Organization for the Reform of Marijuana Laws) published a statement claiming regular users will typically test positive for 2-7 days.
A heavy user may be detectable for cannabis in blood for 7-18 days. This number is much higher than the 7 days many sites are suggesting, however, these numbers are entirely rooted in peer reviewed scientific research. Also, keep in mind that the higher end (18 days) is reserved for extreme cases.
Here’s a study I find exceptionally interesting and important. There is 3 reason’s I’m so interested in this study:
- It was done in 2013. Many of the studies done on the subject are decades old so it’s always good to have newer research.
- The participants used their own weed instead of administered weed. This is important because administered weed is typically very low strength compared to what the general population is smoking. Many of the old studies consider 3.55% to be high-potency (lol).
- This study found some numbers that are much higher than many of the old studies.
Okay, so let’s dive right into it. This study looked at 22 people who self-reported smoking a median of 9 joints per day. Also, all participants reported regular use of cannabis for over a year prior to the study.
The study analyzed 3 different markers for the screening: THC, THC-COOH, and 11-OH-THC. Both THC and THC-COOH were found up to 30 days after subjects stopped smoking. Now, let me say, there were 2 subjects in the study who reported smoking for 15-17 years and 9-18 joints per day respectively. So, keep in mind these are extreme cases. Also, although THC was detectable for 30 days, the cutoff of ≥5 ng/ml for THC-COOH, was not reached after 18 days. The ≥2 ng/ml cutoff for THC was not met after 9 days. Lastly, 11-OH-THC showed 0 participants testing above the ≥2 ng/ml cutoff after 24 hours.
These cutoff numbers are important as they have been cited multiple times as proposed levels for impaired driving in states and countries where cannabis is legal. This means heavy users could test positive for intoxicated driving even if they hadn’t smoked for 16 days.
Hair testing reveals marijuana in your system longer than any other testing method. It’s also a very uncommon test to have done. While it is possible to see a longer history of use, all standard testing methods for hair look at the last 90 days. Also, if you think shaving your head will do the trick then think again. The test can also be done on body hair so you would have to shave your entire body smooth (don’t forget about those eyebrows).
Like blood, the detection times for saliva are much shorter when compared to urine screenings.
The majority of one-time smoker’s saliva will test negative for marijuana in less than 24 hours.
This research took a look at 6 other studies who looked at saliva testing on marijuana users. It found detection times to range from less than 6 hours up to 14 hours.
Niedbala et al found subjects tested positive for 13-34 hours after one-time use. However, this test used a .5 μg/L cutoff level which is double the typical cutoff of 1 μg/L for a GC-MS test.
Due to the small window of saliva detection time most occasional users (smokes a few times per month) shouldn’t take much longer than a one-time user to naturally detox (24 hours).
Using a few times per week may increase your detection time. Olaf Drummer did a meta analysis in which 4 different studies were analyzed. He found the longest detection time to be around 30 hours. So, regular users could possibly test positive for up the 3 days.
Extreme cases could see saliva detectable for up to 7 days, however, this amount of time would be considered unusual. The actual time is going to vary based on your individual variables.
Thanks for reading! Let me know what you think in the comment section below. Also, if you enjoyed this article then here are a few more I think you might like: