THC is the active ingredient in marijuana that’s responsible for the high you experience when smoking or ingesting. Blood levels of this active compound generally leave the body after a few hours.
But unlike other drugs, marijuana use can be detected for months after using. Even your urine will still show traces after a period of time has passed.
Urine tests don’t actually screen for THC. They screen for a particular metabolite that forms after the THC in your blood has been filtered by your liver. Commonly known as THC COOH, this metabolite is taken up by the fatty tissues in your organs. The lungs, heart, liver, kidneys and body fat are all able to store this metabolite. Over time, small amounts of THC COOH are released back into your system and flushed away in your urine and excrement.
However, this process takes a lot of time which is why you can still test positive for marijuana many months after stopping. Of course, the exact length of time depends on several factors:
- THC Potency: If you’re smoking a highly concentrated variety of weed, you’ll accumulate more metabolites in your system. And the more metabolites you have, the longer it will take to eliminate them from your system.
- Frequency and Duration: Frequency refers to how often you use marijuana. Once a week or once a month? Duration refers to how long you have been using for. Three months or ten years? Because the metabolite accumulates in your body and is only released slowly, frequent or long-time users will have more of the metabolite in their system.
- Method of Consumption: Do you smoke marijuana, ingest it in an edible form, or both? Blood levels of THC tend to drop faster if you smoke it than if you ingest it.
Some of the other factors that influence detection levels have more to do with your individual characteristics.
- Metabolism: If you have a faster metabolism your body may be able to process and eliminate the metabolite rather quickly.
- Weight: Because the metabolite is stored in the fatty tissues of the body, the fatter you carry, the more you can store.
- Fitness level: Exercise tends to speed up the metabolism. So if you work out regularly you’ll be able to increase the rate at which the drug is flushed from your system.
- Eating habits: A healthy diet helps your body flush toxins from your system faster. That includes THC.
There is really no conclusive answer to the question of how long marijuana can remain detectable in your urine. Urine testing is most often used to confirm active usage. Samples are analysed for heightened levels of THC COOH. This is measured in nanograms per millilitre (ng/ml).
Urine tests typically have a threshold of 50ng/ml, although some test for even smaller amounts of only 20ng/ml. If the initial test yields a result higher than the threshold, the sample will be sent for further testing by gas chromatography or mass spectrometry. Here the threshold is only 15ng/ml and it is very accurate.
How Long Does Weed Stay in Your Urine?
All the factors mentioned above will vary between individuals, but here are some general estimates you can use (note that these are when no detox efforts are taken, and these estimates can be shortened considerably with a good detox plan):
- A one-time user will often (not always) be able to pass a urine test after seven days, provided they don’t use marijuana again during this period.
- For moderate users it will generally take 1 – 3 weeks for their urine to be clear of the THC metabolite.
- Regular users will need at least 3 weeks of abstinence to ensure a negative result.
- Heavy users will find it considerably more difficult to test clean up since it generally takes anywhere from 1 to 3 months after stopping. Even this is not definite as some heavy users still fail the test after three to six months of abstaining (longer than with any other testing type, hair being 3 months max, duration in saliva and blood being less than 10 days max), although it’s pretty rare.
So even one-time users are likely to get a positive result on a urine test if the test is administered within a few days of smoking. Heavy users will have more of the metabolite circulating through their system all the time. This is why they’re still likely to have a positive test result, even after a long period of abstention.
Some people try drinking plenty of water right before their test in an effort to flush their body and dilute their urine. But this is not really effective. Your body only releases small amounts of the THC into your system over time. Drinking more water won’t speed up this process. And diluting your urine may cause more problems. If a sample is too diluted the lab may reject it. This only makes you look suspicious and you’ll probably have to be re-tested.
It’s also not recommended that you add any other substances to your urine. Liquid detergents cannot alter the chemicals in your urine and may cause it to froth during transportation. Again, this will cause the lab to be suspicious and they may test for the presence of detergent. Bleach also won’t have any effect, and most testers are familiar with this trick.
The only way to 100% ensure a negative result is to stop smoking or ingesting marijuana long before the test is administered. If time is not on your side however, you generally only have two options that are decent depending on the circumstances;
- Go heavy on detox – Combining effective products with natural efforts of sweating through exercise, drinking plenty of liquid, diet etc. On this page you can learn all about this.
- Synthetic urine substitution – Great when you have little time and your test is unsupervised. Needs to be a reliable brand that will pass a lab analysis. I recommend that you check out this page for all you need to know about urine substitution.
Again, light and infrequent users will stand a better chance of passing a urine test if sufficient time passes between their last joint and the test. Frequent and heavier users will need more time to allow the THC to flush from their systems. However, with a proper, sensible detox programme the amount of time needed can be reduced. Exercise, diet and stress management can improve your metabolism and help you shed the drug from your body faster. Take your method of ingestion, frequency and duration into account when working out how long it will take you to get clean. For more info on beating a urine test you can read this guide.