How Long Does Weed Stay in Your System?

When you consume psychoactive cannabis (AKA weed or marijuana), it can stay in your body for quite a while. Depending on the test administered, it can be detected anywhere from hours and days... to weeks and months.
Police drug testing bus

There are a number of reasons why you might want to know how long weed stays in your system. Perhaps you’re concerned about drug testing, or maybe you feel like you need a break to clear out the THC from your body. So then, let’s find out – how long does weed stay in your system?

How long does marijuana stay in your system?

Before we begin, let’s clarify one thing – we’re talking about cannabis as in marijuana, AKA “the stuff that gets you high” due to the presence of the cannabinoid THC. Hemp foods typically contain less than 0.3% THC, so it’s practically impossible that you will fail a drug test from consuming hemp.

Does CBD show up in drug tests?

CBD shouldn’t show up in drug tests. Theoretically, however, one may consume enough Full Spectrum CBD (which includes THC) that it might show up, but this is very unlikely.

The other problem is that due to CBD being illegal here in Australia, it’s only possible to source it from the black market, meaning that it’s impossible to be certain of where it came from and what exactly its chemical makeup is – it may not have any THC in it, or it may have a lot.

Even in jurisdictions where CBD is legal, over half of the 30 products tested in this study contained levels of THC up to double the accepted limit – a point which demonstrates the extent to which Australia will require a highly regulated legal framework to prevent the same thing happening here.  

How long does THC stay in your system?

The short answer is anywhere from 3 days to 90 days.

When people ask “how long does weed stay in your system?”, what they’re really asking is “how long does THC stay in your system?”. This is because when drug testing happens around cannabis, it is generally intended to measure THC levels, since this is what makes people “high” and affects their behaviour and reaction time.

Testing may be carried out by police, workplaces, sports bodies or other authorities. In Australia, people can be tested for illegal drugs in randomised roadside tests which use saliva swabs. Certain workplaces and sports bodies use blood tests and/or urine tests.

Marijuana (aka psychoactive cannabis) lasts a differing amount of time in the body based on a number of factors:

How long does weed stay in your system?
  • How much THC was contained in it
  • How often it’s ingested
  • How long it’s been since it was last used
  • The size and body fat percentage of the individual
  • The individual’s metabolism and how quickly they process THC
  • Levels of hydration

Let’s take a closer look at the different test types:

How long does THC stay in urine?

As detailed in the Clinical Interpretation of Urine Drug Tests from the Mayo Clinic, THC shows up in urine for varying amounts of time depending on when it was last used:

  • 3 days for casual cannabis users (consumes THC three times a week)
  • 5-to-7 days for frequent cannabis users (four or more times a week)
  • 10-to-15 days for chronic cannabis users (daily)
  • 30+ days for heavy cannabis users (multiple times daily)

The reason it can take differing lengths of time is because cannabis is fat soluble, meaning it’s stored in fat molecules in your body. This means that it can take some time before it’s expelled.

How long does THC stay in blood?

For testing purposes, weed traces can be found in your blood as THC for up to five hours, while THC metabolites have a detection time of up to 25 days. The typical time span is 2-7 days.

Even in chronic users, traces of marijuana quickly disappear from the blood. This study looked at 25 long-term users at the US National Institute on Drug Abuse over the course of a week, under continuous medical surveillance to prevent cannabis self-administration. Nine users (36%) showed no traces of THC during 7 days of abstinence while the other 16 users showed at least one positive test.

How long does THC stay in hair?

Hair testing for weed can show usage from up to 90 days prior. However, this sort of testing is uncommon – good news for stoners.

How long does THC stay in saliva?

Differing studies have shown different results, with the research at this link showing THC traces disappearing 15-34 hours after smoking or eating marijuana. Another study demonstrated that casual users show evidence of weed in saliva for 1-to-3 days, whereas THC in chronic users is detectable up to 29 days after use. 

Roadside Drug Testing for Weed, Marijuana and THC in Australia

By far the most common way to end up being tested for cannabis in Australia is via randomised roadside drug tests by police.

Shockingly, the tests have been found to be very inaccurate, with this study showing that it can result in an incorrect outcome up to 16% of the time.  

An article by the ABC quoted Thomas Arkell, a University of Sydney researcher behind the study, as saying “What we found was that these test results often came back positive when they should have been negative, or conversely that they came back negative when they should have actually been positive”. As the article details, the poor standard of testing has resulted in a number of cases being thrown out of court, as the results cannot be tested.

So remember – if you’re pulled over for roadside testing, question the result and do not admit to anything without consulting legal advice. You may have been falsely accused and be able to beat the charge.

That said, do not ever drive while impaired from cannabis consumption – as this study demonstrates, doing so makes you twice as likely to crash. Regardless of your reasons for wondering about how long does weed stay in your system, there’s one thing you should be certain of – don’t drink and drive, don’t smoke weed and fly, and don’t smoke weed and drive!   

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