How Long Does Weed Stay In Your System

There is no single answer to the question. Marijuana can be detected in your system anywhere from a few days to several months depending on a number of variables. How often you smoke, your rate of metabolism and your weight all need to be considered.

On this page I aim to answer the question “how long does weed stay in your system” the best way one can expect. This includes general estimations of detection time in urine, hair, saliva and blood, as well as factors that play a part in how long the THC remains. I’ll also include links to guides on how to pass drug tests by shortening this detection time.

But let’s start with some basics:

What do drug tests look for?

Drug testingTetrahydrocannabinol (or THC) is the chemical compound found in marijuana that is responsible for the ‘high’ you get when you smoke. Once ingested, the body breaks it down into about 80 different metabolites. It’s one of these metabolites, THC COOH, that drug tests usually screen for to determine if you are using (or have been). Saliva and blood tests however, look for the actual THC as opposed to its metabolites, and thus have a shorter detection span.

Unfortunately, THC COOH is extremely hydrophobic. This simply means that water doesn’t stick to it and dissolve it like it does with alcohol. Instead, it gets stored in other compounds, such as alkanes, oils and body fat. Although blood concentrations of THC drop rapidly after consumption, it is stored in organs like your lungs, heart, brain and liver for much longer. In fact, in can remain in the fatty tissues in your body for up to four weeks after consumption.

This means it can take a considerable amount of time before the compound is no longer detectable. And while THC COOH is the primary metabolite that drug tests look for, there are some other compounds that are also used to determine marijuana use.

How quickly is THC flushed from your system?

How long does weed stay in your system

How long does weed actually stay in your system? This depends on a lot of factors as you will learn below. If you’re running out of time due to a drug test though, there are still ways to get around that and speed up the process.

Your liver is responsible for cleaning your blood, which is why THC isn’t detectable in blood after at least three days. Studies show that within 5 days almost 80 – 90% of the THC is removed from the body. More than 65% is excreted in faeces and 20% in urine.

But regular users may still have detectable levels in their blood up to a month later. For very heavy users, this number can be several months.  If you’re facing a drug test, knowing how and when you’ll be tested will help.

Because the THC is taken up by the organs quickly, it is stored in the fatty tissues of your body for much longer. Over time the drug is still flushed from your organs, but it’s a much slower process. And if you’ve been smoking for a long time, you will have built up a significant amount of THC in your body. The longer you’ve been using weed, the longer it will take to completely clear it from your system.

Factors that influence how long marijuana stays in your system

It doesn’t matter if you’re an infrequent user, or if you smoke marijuana every day. There are many factors that can affect how long the weed you smoke remains detectable in your system. Here’s what you need to take into consideration if you’re facing a drug test:

  • THC Concentration Levels: Naturally, the more you smoke the more THC you ingest and this will remain in your system for longer. But the potency of the marijuana is also important. Even a small amount of weed with a higher concentration of THC will result in the metabolites remaining detectable for a longer period.
  • Frequency and Duration: If you smoke regularly, or you’ve been smoking for many years it’s likely that you’ve built up a significant amount of THC in your system. Even if you haven’t been smoking for long, but have had a joint every day, you’ll have higher levels of the metabolite in your body.
  • Method of consumption: If you smoke marijuana, the level of THC in your blood will drop sharply within a few hours. If you ingest it, the immediate heightened levels could remain detectable for longer since it’s metabolized more slowly, although in the long term the duration it stays in your system will still be similar.

These are standard factors that apply to all marijuana users. Yet, there are some other factors that vary significantly between individuals:

Marijuana detox timeline factors

Below factors are responsible for the unpredictability of the time it takes to get your system clear after cannabis use. They are highly individual and could mean that you need twice (or half) the duration to get clean compared to someone else smoking the exact same amount.

  • Metabolism: Some people have a faster metabolism than others. This means their bodies are able to break down and flush the THC faster.
  • Body weight: Your body weight and percentage of fat can influence how long it takes to clear THC from your system. THC is stored in the fatty tissues, so if you have an above average percentage of body fat it will take longer for you to clear your system.
  • Other drugs and supplements: Some substances can slow down the metabolism while others may speed it up. If you’re using other prescription drugs or taking a health supplement, do some research on the ingredients. Your body is constantly metabolising substances from your body, not only THC.
  • Overall health: If you exercise, eat correctly and get enough sleep your body will function better. It will also be able to detoxify itself at a faster rate than if you aren’t taking proper care of yourself. Stress is another factor that has an effect on your metabolism. The more stressed you are, the less likely your body is functioning at its best.

With all these factors at play it’s easy to see why the amount of time it takes for the body to be clear of THC varies so much between individuals. Everything from how often and how much you smoke, to your general health and fitness can influence how long it takes for the drug to be flushed from the body. Even though levels of THC in the blood can fall within a few days of consuming marijuana, it remains in the fatty tissues. It takes much longer for the organs to release the metabolites into your system where they’re finally flushed from the body through your faeces and urine.

On top of this, drug tests look for evidence of marijuana use in different bodily fluids and even hair. Some drug tests are more sensitive than others and are able to detect smaller amounts of THC months after exposure. While some can determine whether a person is currently using, others can show whether marijuana has been consumed in the past.

Knowledge is power. Understanding how the different tests work and how sensitive they are will help you to pass them. THC remains detectable in blood, saliva, urine and hair for different lengths of time. What follows is a quick overview of each test and what you need to know about it.

Testing for THC: The Facts

It seems unfair that employers resort to testing prospective employees for drug use. Often, these tests are only an indication that someone has used marijuana in the past. It’s no indication of their current state of intoxication and doesn’t necessarily guarantee that they are fit for work. Unfortunately, this hasn’t stopped the practice of testing new and existing employees.

Since the time it takes to eliminate THC from the body can be unpredictable, you should abstain from smoking as soon as you are told about a drug test. Then, based on the type of test that will be administered, you can take the necessary steps to detoxify your body. It is essential that you don’t consume any marijuana during the detoxification process.

There are four main substances that can be tested to indicate marijuana usage. They include blood, saliva, urine and hair. Some are more popular than others because they are less expensive, but they vary in accuracy. They are used to determine the levels of the metabolite THC COOH present in the sample. This is usually recorded in the format of nanograms per millilitre (ng/ml).

Each test also has a specific ‘threshold’. Some are set at 50ng/ml while others might be as low as 20ng/ml. If you use marijuana regularly it will take much longer to pass a test with a threshold of 20ng/ml than one with a threshold of 50ng/ml. Here’s what you need to know about how long THC can be detected by the different tests.

How long does weed stay in your urine?

Urine tests are one of the most popular and reliable tests for marijuana use. The threshold for urine tests is usually set at 50ng/ml. They are able to accurately determine whether an individual has used marijuana within 1 to 3 days. Metabolites can be detected in urine within 2 – 5 hours after smoking. The length of time it remains detectable will depend on the frequency of your usage.

A one-time user will generally test positive for one to six days after consumption. Moderate users will likely have levels high enough to be detected after approximately 7 to 14 days afterwards. Frequent users will have to wait at least two to three weeks before they can pass a urine test. Unfortunately, heavy users can test positive for months due to the build-up of THC in their systems.

urine detection time

Of course, this can vary depending on the other factors mentioned earlier, but the fact remains that heavy users will have difficulty passing a urine test. However, infrequent and moderate users can lower the detectable levels of THC in their system by following a sensible detox program. The more THC you can flush from your system before the test, the more difficult it will be to detect.

You might be tempted to drink lots of water to dilute your urine as much as possible. But, if the sample is too weak, the lab may reject it. This will only make you look suspicious, although it might buy you more time before another test is administered.

You can read this page if you want to know you best options of passing a urine test. In the end it comes down to either detox or synthetic urine if you don’t have a lot of time at your disposal to wait it out by staying abstinent.

How long does weed stay in your hair?

Although it can take up to five days after exposure for THC to show up in your hair, it remains detectable for months afterwards. While they’re not a popular choice for detecting recent use, they are used to determine historical use. Even if you haven’t touched a joint for months, the THC that remains in your hair and will give you away.

The most recent outgrowth of hair is used for testing—normally 1.5 inches. It takes hair on average 3 months to grow this far, so the time THC remains detectable in your hair will therefore be 3 months on the vast majority of hair follicle tests. If you have extremely short hair this may compromise the test. But, body hair can also be used. Unfortunately, body hair tends to grow at a slower rate which means it can provide the tester with a longer detection detection time

Hair tests can detect an exceptionally small amount of THC, even as little as 1ng/ml. It is an extremely sensitive test that is excellent for proving a history of marijuana use. Because the metabolite is literally bound to your hair follicles, most shampoos and remedies will have little to no effect at all.

But it should be noted that THC does not always bind reliably to hair follicles. So hair testing may not be considered a reliable or accurate test for marijuana use. They can also be expensive, so most employers are unlikely to use them.

There are ways though (although few) that are considered effective in beating the hair test, by being able to access and open up the hair follicles. Find out more by reading this guide.

How long does weed stay in your blood?

Blood tests aren’t as popular as urine tests because they can be difficult to administer. However, they remain an accurate test for active consumption. They are also used by law enforcement to determine whether someone has been driving under the influence of marijuana or other drugs.


In general, THC is taken up by the liver very quickly and blood levels can drop significantly within a few hours of smoking. However, if you’re ingesting marijuana orally, it can take much longer for the levels to drop. Of course, if you’re a heavy user, even your blood levels will be higher than a once-off or infrequent user.

To pass a blood test, an infrequent user would need 2 – 3 days before ensuring a negative result. And a heavy user would need about one to two weeks to be clear of THC in the blood. There are also ways to detox your blood.

How long does weed stay in your saliva?

Saliva tests are fairly new and not considered as reliable as some of the other tests. There is a small window of detection with this test as only minimal amounts of the drug are excreted through saliva.

Saliva detection time

Generally it is capable of determining whether an individual has consumed marijuana within the last 2 to 3 hours. After 2-3 days of abstaining an occassional smoker should generally be able to pass most saliva tests, although heavier users may need a week of abstinence to be on the safe side.

There are products that can make sure you pass the saliva test though, and you can find out more about that in this guide. If it’s an important test, that can be very useful to eliminate most of the risk of failing.


Cannabis tends to remain in the body longer than other drugs because of its accumulative effort. Most drugs are quickly absorbed and flushed within hours, but because the metabolites from marijuana are very fat soluble they remain in the fatty tissues and are slowly released over a period of time. If you want to detoxify your system, be sure to give it plenty of time and don’t try to rush the process. If time is not on your side and you have a drug test coming up however.. For the most effective ways to detox from THC, make sure you check out the home page!

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