How long does weed stay in your system?

It’s a pretty reasonable question to ask: if I smoke weed now, how long afterwards will it be detectable in my system? The answer can help you increase the safety of co-workers and other drivers, protect yourself against breaking the law, and ultimately, just plan ahead.

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Like many people around Australia, you may have recently heard a lot of debate in the media about driving and cannabis testing.

Most recently, the basis of this debate has been around lobbyist groups querying the validity of the NSW Government advice pertaining to how long THC can be detected using roadside saliva (more correctly oral fluid) drug tests. According to that website, this is around 12 hours. In contrast to this, a magistrate in Lismore has openly criticised the NSW Government’s roadside drug testing program, believing cannabis can be detected in the system for longer than the advised 12 hours. The magistrate noted many people appearing in court for a drug driving offence report not having smoked cannabis for weeks despite returning positive results.

The challenge with cases like this one is a magistrate’s comments can carry quite a lot of weight – but in this instance, those comments are based on the self-reporting of people who have been charged with driving under the influence of a drug – a conviction that carries with it hefty fines and the loss of a licence. To date, this magistrate is the only in Australia to challenge the 12 hour advice – advice that has been reinforced by science. While there has been some other debate around testing for traces of cannabis for 12 hours when intoxication or impairment may not last that long, the best option, like alcohol, is simply to have a plan B if you plan to smoke and drive in the same day.

Despite the presence of mobile drug testing increasing in many states, and many industries such as mining and construction choosing to drug test their employees for safety reasons, it seems people are becoming confused about how long drug tests can detect THC in the system after it has been ingested.

It’s a pretty reasonable question to ask: if I smoke weed now, how long afterwards will it be detectable in my system? The answer can help you increase the safety of co-workers and other drivers, protect yourself against breaking the law, and ultimately, just plan ahead.

But the answer all depends on the type of test being used…

Saliva tests

This is the type used in roadside drug tests, where a swab of the driver’s saliva is taken by police. Cannabis use (THC) can usually be detected for up to six hours depending on the test and person. To play it extra safe though, it’s probably best to stick with the NSW Government’s guideline, which says THC can be detected for up to 12 hours in a saliva test.

Blood tests

THC can usually be detected in blood samples for up to 36 hours after use.

Urine tests

In some cases it’s been said metabolites of cannabis (THC COOH) can be detected in urine for up to 95 days among those people who are heavy users, but more commonly this type of testing shows use anywhere between 34-87 hours.

Hair tests

Hair follicle testing is not as clear cut when it comes to cannabis. Because THC doesn’t readily accumulate in hair, detection rates vary between daily users and non-daily users.

Breath tests

This is a new and developing area and is not yet used routinely. At this stage THC can be detected for one-to-two hours after use among those using regularly, however the test can be less reliable for occasional users.

Keep in mind, these are only indications. Everyone is different, as is their cannabis frequency and volume of use. Many factors can have a big effect on how long cannabis remains in your system, so it could be longer or shorter than the indications above.

So there you have it. Some tests detect THC directly and other its metabolites or breakdown products; and the length of time needed to avoid detection varies greatly between all of them. Of course they don’t test for impairment, which is another issue entirely. It’s important to remember that saliva tests are very reliable, and even if you’re personally sceptical , they are still used by law enforcement and that is unlikely to change any time soon.

Your best bet to avoid cannabis being detected in your system by any of the tests mentioned here is to avoid using cannabis altogether!

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