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If I Smoke Weed Once, Will I Fail a Urine Test?

Many occasional smokers think they will fail the urine drug test because they smoked weed once before. Could this be true? The answer is complex. Therefore, read on, as we break down this question into smaller parts.

Table of Contents

How Long Does Weed Stay in Your System?

Whether you smoke occasionally or are new to cannabis, having information about how your body reacts to weed is essential.

Marijuana contains THC (delta-9 tetrahydrocannabinol), a psychotropic or euphoric substance that stimulates part of your brain and causes a “high.” A drug test is not usually administered to detect the THC molecules in your urine but rather the waste products your body produces after smoking weed.

When you smoke marijuana, THC metabolizes in your body, which gets you high for a few hours as your body processes the psychoactive content. The end products, which are called metabolites, store in your fat cells and organs of your body from several days to several weeks until fully clean. The time it takes for the metabolites to clean from your system depends on how often you smoke, your metabolism, and the amount of fat you have in your body.

How Much You Need to Pass a Urine Test

A urine test is considered noninvasive and relatively accurate. Technically, weed doesn’t stay in your urine, but its waste products do. A urine drug screen for marijuana contains immunoassays with antibodies that are made to detect THC’s main metabolite 11-nor-delta-9 Carboxy-THC (THC-COOH).

The accepted cutoff level for THC-COOH in a urine test is 50 ng/mL, which means that your result is considered negative if you have less than 50 ng/mL; otherwise, it’s positive. When the initial urine screen is positive, a Gas Chromatography/Mass Spectrometry test will be used to verify the result at a cutoff level of 15 ng/mL.

How Much Is 50 ng/mL?

CarboxyTetrahydrocannabinol is the most abundant metabolite that stores in the system and ultimately the compound of interest during a urine test. According to studies, the average joint gives about 150–200 ng/mL peak concentration of THC-COOH in urine 4 hours after smoking. So, 50 ng/mL is about one-fourth or one-third of a joint, but it strongly depends on your cannabis potency.

THC Half-Life

Half-life is the time frame it takes for a substance to reduce by half its initial value. The half-life of THC is not the same as how long you stay “high.”

The half-life of THC in urine is about 30 hours, which means that THC concentration in urine is reduced by half about every 30 hours. So, having 200 ng/mL after smoking a joint will give you about 100 ng/mL the next day and about 50 ng/mL 2 days after smoking.

This calculation is very rough because half-life depends heavily on many factors, such as:

  • the route of administration
  • the frequency of marijuana use
  • body structure
  • drug potency
  • fluid intake
  • metabolism rate

Will I Pass a Drug Test If I Smoked 1 Week Ago?

Regardless of all the information about whether or not you will pass a drug test, it still depends specifically on your body and the potency of marijuana. In most cases, a week is long enough to flush THC out of your body. So, yes, if you smoked only once, you are very likely to pass a urine test after one week. After 2, 3, 4, and more weeks, chances are 100%, but 1 week is also close to 100%.

Will I Pass a Drug Test If I Smoked Weed a Few Days Ago?

The short-lived effect of THC does not prevent evidence of marijuana from lingering in your body. For as long as the chemical exists in your body, you risk failing a drug test. If you had smoked weed just a few days ago, your chance of passing is 50–50, depending on the potency of the marijuana and your metabolism. Having a few puffs will give you a THC-COOH level under 50 ng/ml in 1–2 days. After one joint, you can pass the test in 3–5 days.

Can I Pass a Drug Test the Next Day?

The time it takes for weed to get out of the system depends on how often, how much, and for how long the user has been smoking. If you don’t have a history of marijuana smoking and you had just a few puffs, it’s possible but not guaranteed that you will pass a drug test the next day. After a joint or even half of a joint, you will fail.

Can I Pass the Urine Test in a Few Hours?

Surprisingly, yes. As was said before, urine tests check for THC-COOH, not THC itself. THC-COOH is a metabolite of THC, and the body needs some time to metabolise THC into THC-COOH and excrete it through urine. According to studies, the peak concentration of THC-COOH in urine comes about 4 hours after smoking. So, 1–2 hours may not be long enough to accumulate 50 ng/mL in urine so that you can pass. This is why saliva tests are used to detect recent cannabis use.

So, the main question is:

Will I Fail a Urine Test If I Smoke Weed Once?

Several factors can improve or decrease your chances of passing a drug test. Studies have shown that occasional smokers can pass a urine test in a few days.

If you had just 1–2 puffs, the chances are that you will pass even the next day if your strain was weak.

If you had a full joint, you would fail in the next few days, but it’s impossible to say for sure how many days you would need to get clean. It depends on weed potency and your metabolism.

You will pass the urine test for sure about one week after smoking weed once.

Important Notice

This information is for only one smoke, not for regular users! Even if you had smoked a few weeks ago, some residue might stay in the body and affect test results.

The calculations above are rough. In the end, it all depends on weed potency and your metabolism! You should not rely on this information when preparing to pass a drug test.

To know if you are ready for a drug test, you need to be able to determine the number of metabolites in your urine. You can use the THC calculator to calculate your approximate level of THC-COOH. It also helps to understand the probability of passing a test.

When your chances of passing a drug test are slim or you are not sure about the result, use THC detox kits that clear THC metabolites from your system. They include high-quality detox drinks that will help dilute your urine. These detox drinks contain vitamin B and creatine that will help hide that your urine is diluted.

Many occasional smokers think they will fail the urine drug test because they smoked weed once before. Could this be true? The answer is complex.

How Long Does Weed Stay In Your System?

This article was made possible by a sponsorship from my friends over at passyourtest.com. Check out their site to find out how to reduce the amount of time THC is in your system.

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.

Here’s a text version of the chart above for those who are unable to view images:

Urine
Single Use 2-7 days
Occasional Use (few times per month) 7-20 days
Regular Use (few times per week) 20-30 days
Heavy/Extreme Use (daily+) 30-100 days*
*60+ days is considered highly unusual even for heavy smokers, but numbers as high as 95 days have been observed in clinical tests.

Blood
Single Use 1-2 days
Occasional Use 1-3 days
Regular Use 2-7 days
Heavy/Extreme Use 7-18 days

Hair
90 days. While it is possible to see a longer history of use, all standard testing methods for hair look at the last 90 days.

Saliva
Single Use 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.

[ps2id target=”/] THCCOOH & What It Means For You

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.

[ps2id target=”/]Factors That Affect THC Detection Times

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.

[ps2id target=”/]How Long Does Weed Stay In Your Urine?

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.

[ps2id target=”/]Additional Factors Affecting Urine Tests

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.

[ps2id target=”/]If You Only Smoked Once / Took One Hit

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.”

[ps2id target=”/]Occasional Use

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.

[ps2id target=”/]Regular Use

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.

[ps2id target=”/]Heavy Usage / Extreme Cases

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.

[ps2id target=”/]Detection Times For Marijuana In Your Blood

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.

[ps2id target=”/]One-Time Use

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.

[ps2id target=”/]Occasional Use

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.

[ps2id target=”/]Regular Use

NORML (National Organization for the Reform of Marijuana Laws) published a statement claiming regular users will typically test positive for 2-7 days.

[ps2id target=”/]Heavy Use / Extreme Cases

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:

  1. 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.
  2. 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).
  3. 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.

[ps2id target=”/]How Long Does THC Remain In Hair Follicles?

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).

[ps2id target=”/]How Long Is Weed Detected In Saliva / Mouth Swab?

Like blood, the detection times for saliva are much shorter when compared to urine screenings.

[ps2id target=”/]One-Time Use

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.

[ps2id target=”/]Occasional Use

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).

[ps2id target=”/]Regular Use

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.

[ps2id target=”/]Heavy Use / Extreme Cases

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.

If you’re trying to reduce the amount of time THC stays in your system don’t forget to check out passyourtest.com.

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:

How long is weed in your system? This article covers urine, blood, hair, & saliva testing. Get times for one-time users, occasional, regular, & heavy users.