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.
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.
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?
So how long does weed stay in your system? It depends on which system we’re talking about. From a certain perspective, humans appear hard-wired for cannabis. We have an endocannabinoid system throughout our body with receptors that perfectly fit the cannabinoids we ingest when we consume weed. And our bodies process those cannabinoids in a variety of ways, producing byproducts that can linger for a long time.
Overview: How Long Does Weed Stay In Your System?
Whether you’re new to cannabis and curious about how long the effects last and how long weed stays in your system, or facing a drug screening of some kind, knowing the specific ways weed interacts with your body and where signs of your using it show up is valuable information.
We’ll answer the perennial question—how long does weed stay in your system?—by taking a look at the four parts of the body that betray the signs of marijuana use.
But before diving in, let’s put the answer as simply as possible.
Remember, it’s technically the psychoactive, high-producing THC that makes your weed illicit, and your use of it illegal. And that illicit chemical is rapidly metabolized by your body when you smoke weed.
The process takes a little longer if you ingest cannabis, but the result is practically the same. You don’t stay high for days at a time because your body quickly processes all the psychoactive compounds you inhaled or ate.
But the byproducts of that process, called ‘metabolites,’ can stay in your fatty tissue for a long time. They’re not active, of course, but they’re telltale signs of previous cannabis use.
So again, how long does weed stay in your system? It depends what the system deals with, THC or its waste metabolite, THC-COOH.
If the system deals with active, or delta-9 THC, weed doesn’t stay around for very long. But if the system deals with eliminating inactive THC-COOH, weed sticks around for a longer time.
How Long Does Weed Stay In Your Blood?
Let’s start with the system that shows signs of weed for the shortest amount of time. That’s your circulatory system, or more specifically, the blood flowing through it.
THC and other active cannabinoids have to make it into your bloodstream to take effect. When you smoke, that happens via your lungs. When you ingest weed, that happens through your stomach.
In other words, your blood is where potent, active cannabinoids make their way to your brain, kicking off the euphoric sensations of being high, or the therapeutic effects in the case of cannabidiol (CBD).
Your body rapidly metabolizes, breaks down those active cannabinoids in the blood. And that’s why signs of weed use don’t stay in your blood for very long.
Hence the reason why companies or law enforcement will take blood tests after workplace or traffic accidents because it would reveal that someone was likely intoxicated with cannabis when the sample was taken.
Specifically, weed (i.e. THC) stays in the blood for one to two days after a single use. If you smoke multiple times or regularly or multiple times daily, weed will stay in your blood for up to a week after your last session.
How Long Does Weed Stay In Your Saliva
Saliva is virtually tied with blood in terms of the time span weed sticks around in it. No wonder a mouth swab drug test looks for the same active THC blood tests do.
Delta-9 THC, the psychoactive kind, coats the inside of your mouth and gets soaked up by your saliva glands after you smoke. If you eat edibles, your exposure is somewhat reduced, but you’re still chewing the decarbed cannabis in your cookie.
This THC doesn’t make it into your bloodstream in any significant quantity. It just stays in your saliva until you swallow enough of it to purge your mouth of the signs of your scandalous cannabis habit.
Therefore, drinking lots of water, brushing your teeth, using mouthwash, and eating fatty foods—THC bonds to fat—can help you get rid of THC in your mouth faster.
Specifically, THC will stay in your saliva for one to two days after your last puff. If you’re worried that you smoke a lot, or if your weed is more potent, traces of THC could linger up to a week, max.
How Long Does Weed Stay In Your Urine
As you can see, your body is naturally eager to absorb and process psychoactive THC and other active cannabinoids. (Drug tests, by the way, are only looking for THC.) So those chemical compounds of weed don’t stay in your system very long.
But the byproducts of THC, which are evidence of prior use, are also fat-soluble. In other words, THC metabolites bond to fatty tissues, and this causes the body to take some time expelling them.
So technically speaking, ‘weed’ doesn’t stay in your urine, THC-COOH does. And it’s totally inactive, meaning you’re not still under the influence of cannabis despite the presence of this chemical in your system.
Since the presence of cannabinoid metabolites in the body is entirely dependent on a person’s particular traits, it’s hard to answer definitively, how long does weed stay in your system?
Suffice to say, the amount of time evidence of cannabis use stays in your urine largely depends on how often you smoke up. Other factors, like your body mass index, your metabolic rate, and how hydrated you are also play a role.
Summing up the research we examined, this table can help you determine the average time weed will stay in your renal system.
- 1-time use: clean in 5-8 days
- 2-4 times a week: 11-18 days
- 5-6 times a week: 33-48 days
- Daily use: 50-65 days, up to 77
Cleanse Using a Detoxification Program
If you have at least seven days before your test, a detoxification program will speed up the body’s natural cleansing process and completely rid your body of the THC in your system in about a week. These programs also come with home testing kits to verify you are clean.
Cleanse the Same Day
If your test is coming up sooner, certain detox drinks are known to flush your system the same day you drink them keeping you clean for a period of four to six hours.
How Long Does Weed Stay In Your Hair
Although there are plenty of myths and misconceptions circulating about hair drug tests, they’re feared by weed users for good reason.
Evidence of cannabis consumption stays in your hair for longer than any other system in your body. In fact, hair follicle testing can reveal cannabis use up to years prior.
But in terms of common testing procedures, hair follicle tests are typically looking for cannabis use back 90 days.
One rumor is that drug test kit administrators or police will cut off the tips of your hair for a drug test. But that wouldn’t be very conclusive at all.
Instead, hair follicle tests take a head hair from the root to 1.5 inches of hair. Testers discard the rest of the hair.
Human head hair grows, on average, at a rate of about .5 inches per month. So 1.5 inches equals about three months of hair growth. If you took the end of a foot-long hair, you’d be able to detect weed use back two years!
Body hair, which grows more slowly than head hair and isn’t replaced as often by new hairs, may betray prior weed use back even further.
A body hair of the same length could show weed use back 180 to 360 days. At the moment, however, there are no conclusive studies verifying this.
So weed stays in your hair for a long time. But it doesn’t show up in one time or occasional users. Instead, hair testing reveals a chronic habit of marijuana consumption.
For regular cannabis users, this is definitely case for alarm. Once THC makes its way to the follicle and ends up in the hair strand, it’s there forever.
Of course, you could answer how long does weed stay in your system with the answer, not another second. All you have to do is shave off all of your hair.
The Final Answer: How Long Does Weed Stay In Your System?
The short-lived effects of weed don’t prevent evidence of marijuana consumption from lingering in your system. Of course, this doesn’t mean that you’re high for as long as those chemicals exist in your body. But it does mean you’re at risk of failing a drug test.
So how long does weed stay in your system? When it comes to saliva and blood, where active THC resides, weed stays in the body for a week, tops. But with urine, weed stays in your system much longer. And with hair, it’ll stay with you forever. Or at least until you cut that hair off!
The human body is a complex machine. And cannabis interacts with it in complex, dynamic ways we don't yet fully understand.