As it becomes legal around the world, everyone is wondering “how long does marijuana stay in your system?” or, taking it a step further, “how long does THC stay in your system”?
The answers vary and are, quite often, all over the map.
Older research says a minimal amount of marijuana use takes anywhere from 25 to 67 days to clear out of your system. However, tests with a higher threshold can show up negative after just 2 days, in some cases.
The answer to this age-old question, unfortunately, is “it depends.”
Factors that affect your detection rate include: your body weight, your level of physical activity, how often you consume cannabis, your consumption method (e.g. smoking vs vaping), the strains you use, how much water you drink, and much more.
It’s difficult to know if you will test positive, even if you do everything “right” to ensure there’s no weed in your system. Worse, common drug testing methods produce false positives in around 5% to 10% of cases.
Want a method for estimating the answer to “How long does marijuana stay in your system”? Read further to learn about how different tests work, the factors that affect them, and what your “safe” window could be.
How Long Does THC Stay in your System?
There are lots of different types of marijuana drug tests. The detection method can affect how long marijuana is in your system. Different tests will yield different results.
The most commonly used methods include:
- Urine test (urinalysis)
- Hair test
- Blood test
- Saliva test
It’s important to note that all test types are trying to detect a certain molecule at a certain concentration.
Molecule concentration is often written as a nanogram per milliliter (ng/ml) figure. So, for a saliva test, a cutoff of 20 ng/ml means that the test will be POSITIVE if more than 20 nanograms’ worth of THC is detected in a milliliter of saliva.
A nanogram is a billionth of a gram, which is pretty tiny. Yet, tests looking for over 50 ng/ml can often show negative after just 24-48 hours of smoking. On the other hand, tests looking for a tiny 20 ng/ml amount will show up positive more often.
Learn more about how each test works below…
Urine Tests (Urinalysis) for Marijuana
Urine tests look for the presence of THC metabolites, usually THC-COOH. These metabolites form when your liver breaks down the THC in your system, after ingesting cannabis. Your kidneys filter out these molecules, and then your body gets rid of them through your urine.
As a result, urine tests do not detect whether or not you are high during the test. Instead, they just indicate that you have been stoned at some point recently in the past. Testing sensitivity commonly ranges anywhere from 15 ng/ml to 90 ng/ml.
Urine tests expose the urine to chemicals that change color when THC-COOH is present or not, depending on the test. Less-accurate tests use litmus strips that react upon contact with the urine.
Gold standard tests use gas chromatography/mass spectrometry (GC/MS). Urine is vaporized into a cloud of molecules, and a computer system measures the range of molecules and ionized particles. Then, using the results, they look for THC-COOH and other molecules.
Note also that urine tests look for signs of tampering. Not only will they test for THC-COOH, but they will also look for:
- Diluted samples (examining color and consistency)
- Added chemicals (adulterants)
- Temperature (to see if it’s actually fresh urine)
- Chemical makeup (to see if the sample is old, artificial, not the same person, etc.)
How Long Does Marijuana Stay in Your System for a Urine Test?
THC metabolites, like THC-COOH, are fat soluble. This chemical property means that the molecule will not break down in water, nor can it exit your body through water alone.
When THC-COOH gets filtered through your kidneys, most of it is reabsorbed into your bloodstream. But, some of it gets stuck behind. These “stuck” molecules are chemically changed by your kidneys to become more water-soluble before you urinate them out.
As a result, THC-COOH takes a loooooong time to break down and exit your body. It will also have higher concentration in your kidneys than in your bloodstream. Additionally, smoking high-THC marijuana strains will naturally concentrate THC-COOH further.
So, exactly how long does marijuana stay in your system for these tests?
According to California NORML, someone who rarely smokes marijuana should have all their metabolites leave by 1-7 days for a 20 ng/ml test.
However, someone who smokes regularly will have to wait at least a week, and it could last as long as 100 days — more than three months!
Note that drinking plenty of water, engaging in physical activity, ceasing cannabis consumption, and drinking mildly diuretic substances like cranberry juice can all potentially help shorten the duration that THC-COOH is detected in habitual users through urinalysis.
Other Tests — Blood, Hair, Saliva, Etc.
There are other tests that check marijuana and THC in your system. These include blood tests, hair follicle tests, and saliva tests. Details for each are below:
- Blood tests look for actual, active THC. The simple litmus strip test can only detect concentrations 50 ng/ml or higher. The GC/MS can detect down to 15 ng/ml. So, how long does THC stay in your system?
- Light users: 12-24 hours
- Heavy users: 2-7 days
- Hair follicle tests use GC/MS to find metabolites in your hairs. They can detect them at a level of 1 picogram (a trillionth of a gram) per milliliter of hair by volume. How long does THC stay in your system?
- Light users: Will not typically show up on hair test for single use
- Heavy users: Can last 90 days or more.
- Saliva tests typically detect 15-20 ng/ml of THC in mouth fluids. The test measures marijuana metabolized into saliva through the bloodstream. It can detect use as recently as three minutes ago. However, results for detection are inconsistent, depending on the test brand. How long does THC stay in your system?
- For both light and heavy users: 24-72 hours, max
Cannabis Options for Lower Risk of Drug Test Positives
There is no 100% guarantee to test negative on any drug test after consuming cannabis in the past few months. However, you can look to pure CBD products, low-THC weed strains, and high-CBD weed strains to lower the amount of THC you consume.
All in all, we hate the fact that responsible adults have to worry about a test that just detects that they got high recently, not that they are high now. We wish you the best of luck on your upcoming test, and we sure hope reading articles like this helps!