Using activated charcoal to clear your system of THC and its metabolites is still controversial. Here is the science showing why it works.

I have focused so much recently on busting drug testing myths, that it is time to get down to some things that actually work. Today I will focus on a strategy to beat cannabis drug tests that has the reverse problem…many people don’t believe it even though it is proven to work!

I am talking about activated charcoal. Activated charcoal is a very porous type of carbon. It has a large surface area to which drugs will adsorb. It is frequently used in the emergency room to soak up drugs like a sponge in the GI tract in cases of poisonings and overdoses. It is also available over the counter as a powder, in capsules, and in drinks.

It might not hurt to keep some activated charcoal around in case you accidentally take too high a dose of edibles. Without a doubt it is effective at stopping drugs still in your intestines from being absorbed. But when it comes to drug testing, nobody can agree on whether it works!

There is so much misinformation! Vice tried to investigate it, but the expert they consulted got it wrong:

“As for the activated charcoal pills, it turns out that I may have been led astray by the internet…he told me that, basically, they’re bunk.

Herb suggests that it works, listing it as something that can be done a few days before the test:

“Some additional helpful supplements to try a few days before a test include…activated charcoal (only if the THC is still in your digestive tract)”

What the f*** are they even talking about? If you know you have a drug test coming up in a few days, why would you be taking an edible?

Even on a number of websites where physicians answered this question, they all gave wrong information:

“If you are asking if taking charcoal in order to pass a drug test – there is no basis to believe that this would have any significant effect on the levels or length of detection of common drugs in urine, hair or saliva tests”

Most of this confusion comes from a lack of knowledge about the properties of THC metabolites. That is why I am here to drop some science and set the record straight.

Enterohepatic Recirculation of THC Metabolites

The fundamental misunderstanding about whether activated charcoal works comes down to one question. After THC has been completely absorbed, do its metabolites go into the GI tract where they can be absorbed by the activated charcoal? Most people think that’s not possible, but the answer is yes. The reason why: enterohepatic recirculation.

Enterohepatic recirculation of THC-COOH

After you ingest cannabis, your body converts THC to the THC-COOH metabolite and then the THC-COO-glucuronide metabolite. The addition of the glucuronide is like a tag that targets the metabolite to be removed from your body. It is excreted into your urine and is the primary metabolite detected in drug tests.

It is also sent into the bile by your liver. Two studies (here and here) have tested the bile of cadavers for THC and metabolites. The THC-COO-glucuronide metabolite was found in incredibly high levels in the bile with a median concentration of 17 uM. Your body produces about 600 mL of bile every day, so this is the equivalent of about 3 mg of THC excreted into your GI tract on a daily basis.

What happens to the metabolite once it is in your bile? Upon eating a meal, your body secretes bile into the GI tract. Since glucuronide metabolites are large and polar, they cannot be reabsorbed from the intestine. The idea is that it will be excreted in your feces. However, thanks to enzymes produced by the bacteria in your gut, most of the THC-COO-glucuronide is converted back to THC-COOH. The THC-COOH metabolite is then reabsorbed into the blood, where it can start the entire cycle over again.

This quantity of THC metabolites circulating through your bile and intestines represents a significant store that is completely separate from the commonly known fat storage. However, unlike the THC metabolites in fat that are basically inaccessible, we can use activated charcoal to interrupt this recirculation and clear the THC metabolites from our bodies. Once activated charcoal binds the metabolites, then they cannot be reabsorbed and you will poop them out.

Does Activated Charcoal Bind THC?

One obvious prerequisite for activated charcoal to work is that it needs to bind THC metabolites. One study assessed this and showed that it does. 5 mg of activated charcoal was able to completely bind 1 mg of either the THC-COOH or THC-COO-glucuronide metabolites (and maybe even more, but they only tested up to 1 mg).

Dietary fiber (in the form of wheat bran) was also able to bind these metabolites. Although an appealing alternative to activated charcoal, a lot more was required – even 250 mg of wheat bran was not able to bind all of the THC metabolites. Fiber also did not bind the glucuronide metabolite as well as THC-COOH.

Clinical Evidence that Activated Charcoal Removes THC Metabolites

Based on the above information, we have a strong, although theoretical, reason to use activated charcoal. But it gets better…a full clinical study was conducted just to see the effects of activated charcoal on THC metabolites. It does not get any better than this!

Eight subjects were dosed intravenously with the THC-COOH metabolite on two occasions. They were randomly assigned to receive the first dose with or without activated charcoal and then crossed over to the other condition on the second dose.

They dosed 5 g of the activated charcoal at 6 different timepoints: 15 min before the THC-COOH dose and 5 min, 2, 4, 7 and 10 h after the dose (for a total of 30 g charcoal).

Activated charcoal reduced serum THC-COOH metabolite levels by 45%

By 24 hours after the dose, the serum THC-COOH concentrations were 45% lower when subjects were treated with activated charcoal.  I suspect that if activated charcoal was given continuously, rather than just for the first 10 hours, the concentrations would have continued to separate further.

Activated charcoal reduced the amount of THC-COO-glucuronide metabolite excreted into the urine by 21%.

The amount of THC-COO-glucuronide excreted into the urine was reduced 21% with the activated charcoal treatment.  THC-COO-glucuronide also reached undetectable levels in urine a full day earlier with activated charcoal.

Again, this is after just a single day of activated charcoal dosing. I expect results would be even better with multiple days of dosing.

Using Activated Charcoal to Clear Your Body of THC Metabolites

Here is my recommended regimen of activated charcoal to reduce levels of THC metabolites and prepare for a drug test:

  • Take 10 g prior to each meal of the day (a total of 30 g a day).
  • Activated charcoal carries a risk of constipation. Take it with plenty of water.
  • If you do experience constipation or other side effects, you can reduce the dose to 5 g prior to each meal.
  • Take the activated charcoal for 2 consecutive days each week, and then take a 5 day break.
  • On the days that you do not use the activated charcoal, eat meals with a lot of fiber or take fiber supplements.
  • Repeat this regimen from the time you want to detox until the time of the drug test. The more time you have, the better.
  • Activated charcoal may bind to medications and dietary supplements and prevent their absorption. Consult your physician if you take medications.

Last modified: May 2, 2017

28 Responses to " Activated Charcoal – Why It Clears THC Metabolites "

  1. Fred says:

    Thanks Prof !

  2. T says:

    Wow, your site is a welcome oasis in the horrendous desert wasteland of credible/helpful ‘info’ on the topic of THC testing–thank you!!! I hadn’t heard about charcoal before and, having a test coming up in the next week or so, and 10 days clean right now, of course I’d like to give myself every chance so thought I’d try it (I’m fairly fit/thin, so going the fat-burning exercise/diet route).

    However: I purchased an over-the-counter bottle of activated charcaol, CharcoCaps. The recommended dosage says 2 capsules per meal/use, which is 520 mg, and says not to exceed 16 capsules per day, which would be 4160 mg. But your recommended dosage is 10 g per meal/30 g per day…that’s about 116 capsules a day, more than a bottle a day and over 7x recommended dosage! Is this really correct?? Is this good for you??


    • Hi T,

      Thanks for your kind words.

      CharcoCaps are made to treat gas and bloating, which don’t require a high dose. 30 g per day for 2 days is perfectly safe (although constipation is possible). It is actually much lower than the doses used in the ER for poisoning. That being said, we don’t actually know what the minimum effective dose is to remove THC metabolites. I recommend 30 g since this was the dose used in the clinical study that I cite in this article.

      I would probably use a different brand based on how small the capsule sizes are. When I have time, I am going to do some research into the best brands for this use and post them.

      • bp says:

        I’m also super-grateful for your work here, Prof! I’m almost 2 weeks clean in preparation for an upcoming test. I’m most likely clean anyway, since I’m pretty moderate and smoke low-THC high-CBD strains, but doing your weekly regimen just to be safe. Last weekend I took a ton of capsules and did have the common side-effect. This past week, though, I found coconut charcoal in powder form, and am finding it’s a lot more economical, convenient, and pleasant than slamming 20-100 pills. The product I found was available at a Natural Grocers. I’ll post again at some point and let you know if the side-effects are better with the powder. It doesn’t taste great, but I definitely prefer it to all the pills.

        • I agree that this probably isn’t so good in pill form. The pill sizes are just too small and so you have to take too many. It seems like buying the powder is the way to go.

  3. G H says:

    Great article! It was very helpful. One thing I’m not clear about is the effect of activated charcoal on thc-cooh that’s already stored in fat. Will activated charcoal help to reduce it if taken over the course of a couple of weeks? It makes sense that it would reduce it in the study where the thc-cooh and activated charcoal were introduced into the subjects at the same time. Thanks!

    • You make a good point that the study does not perfectly recreate the situation of someone who has taken cannabis since they intravenously infuse the THC-COOH metabolite directly. However, I am fully confident that it would still work for someone who has taken THC. As I point out in the article, THC-COO-glucuronide was found in very high levels in the bile of cannabis users. This indicates that a lot of enterohepatic recirculation is happening in cannabis users. If you use activated charcoal to block this cycling, then you will get lower blood THC-COOH levels since little will be reabsorbed from the GI. The more you lower blood levels, the more will move out of fat, since fat and blood levels are always in an equilibrium

  4. bp says:

    One other question for you–you mention taking fiber supplements on days when you’re *not* taking the charcoal. Is there any reason not to take fiber on days when you are? Might the extra fiber interfere with the absorption of thc-cooh into the charcoal? Doesn’t seem like this would be the case, but just want to make sure.

    • There’s no reason you can’t eat fiber every day (in fact it’s probably good for preventing any possible constipation from the activated charcoal). It’s just that it probably won’t do anything extra since the activated charcoal is so efficient at adsorbing the THC metabolite molecules.

  5. bp says:

    Hi Prof,

    Thanks for all your quick responses and all the solid info. One last question before my test–I’m not planning to drink a ton of water before my test, but I tend to stay pretty hydrated, and don’t want to produce a dilute sample because it just won’t look very good. Is it a myth that eating red meat in the 24 hours before giving the sample will raise creatinine levels and reduce the odds of it testing as diluted? Also, does it make sense to drink gatorade vs. water or simply eat something salty to raise specific gravity? I don’t really want to take B complex vitamins because they make urine neon and i doubt u/a labs are just looking at samples to determine if they’re dilute (as opposed to testing creatinine & SG, which I know Quest does). See for more info.

    • Funny you should ask this, because I am starting to research another article on this exact topic. You should definitely be hydrating right before the test to the maximum amount possible without failing the specimen validity testing. The problem is that no one gives any advice based on science about what a good regimen is. Eating red meat should increase urine creatinine, but I haven’t yet looked into how much and for how long. Gatorade is probably better than water so that more electrolytes are in the urine to increase specific gravity, but probably lots of things can raise specific gravity. The B vitamins couldn’t hurt, as I think a tester could reject a very clear sample as being diluted based on visual inspection. I wouldn’t depend on this alone though. I hope I can give you some better advice soon when I finish researching and writing the article.

      • bp says:

        Hi Prof,

        I already took the test, and am pretty sure I passed since I home-tested (voiding half my bladder immediately before going in to submit sample) w/ a nice bold line. However, my urine was ‘straw-colored’ and not really yellow, so I’m concerned it could be identified as dilute. I did eat a nice big bowl of beef Ramen (w/ extra beef) the night before to increase creatinine, sipped powerade in the hour before (didn’t drink more than 20 oz in the 1.5 hrs before testing, though), and had a bag of salted peanuts in the hour before to increase SG. I’m probably not going to smoke until I hear from HR, but have been poking around the internet anyway trying to figure out my odds of having a dilute sample and needing to retest… Looks like I’ll be fine since I didn’t exactly chug water, just stayed hydrated, but better safe than sorry for now…

        Anyway, in my obsessive researching I found this manual for MROs which might be helpful for your articles in general:…/MRO_Manual_2010_100908.doc Also found this study on plasma creatinine following meat meal, which might help with the article you’re working on:

        Quest is a SAMHSA-certified lab. It looks as if a dilute/positive/invalid sample triggers Medical Review Officer (MRO) to call “as soon as possible” and “usually within 24 hours” of such results, so, if I don’t hear from an MRO w/in a few business days, I should be good, right?

        Clearly not in a rush to smoke,


  6. x says:

    Dear Prof of Pot,

    You are truly amazing, seriously thank you for clearing up so many misconceptions about drug testing while providing beneficial information to beating one. It sucks abstaining from smoking, but reading your articles makes it suck less. Thanks a toooooooooon!!!!!!

  7. KD says:

    How can i tell how much im getting per use/dose? Im reading some of the labels for powders i see on amazon etc and i see no concentration information. Thank you so much for scientifically based information!

    • Prof of Pot says:

      If you are using powder, you can divide the size of the package by how much you want to take. For example, if you buy 100 g of powder and take 10 g with each meal, then take about 10% of the package each time. It doesn’t have to be super exact.

  8. NotRichardNixonsBitch,Bitch! says:

    Anecdotal evidence for you:

    160 pounds 6’2″ male. Pre-employment drug screening. Smoked multiple times a day for years, maybe an average of .25 – .5 grams a day. Found out I had a drug test. Abstained completely for 5.5 days. Took about 10 grams of activated charcoal once a day the last two whole days. On the day of the test I drank more water than any sane person ever should – was pissing about every 20 minutes – started hydrating 5 hours before the test. 2.5 hours before the test I drank a XXXXXXXX “detox” drink. PASSED THE TEST THANK DOG! Now I get to start a new career after a lifetime of hard work in school. Thank you for offering this well reasoned and researched information!

    A note to anyone reading this. I currently have no idea how to view the results myself. It is entirely possible that my employer saw the results and decided to gloss over the THC if it was there. Although I doubt this happened since they are a large well known staffing agency and I am now being employed by a fortune 500 company.

    PotProf – please write an article about overhydrating immediately before the test, as I feel this is an effective technique if done safely and in combination with a nutrient beverage such as XXXXXX to offset a possible ‘dilute’ sample.


    • Prof of Pot says:

      Wow, you passed in very little time for how much you smoke! It’s probably a combination of all things – low body fat, charcoal, and drinking a ton of water. I have an article on overhydrating half written, but I’ve been working on some other topics lately and haven’t had time to finish it. Everybody should be diluting their urine before the test though. I am going to give details on exactly how much to drink and what else to take so that you don’t run into issues with low creatinine, low specific gravity, etc. Hopefully I can finish it up by next month.

  9. Jusswavy says:

    Am I being sabatoged? The drug test I tested for my urine and came at a metabolite level of 47 I believe this is the third time it came back on the same level!!! It’s been then 70 plus days since I smoked weed an I weigh like 105 and very skinny but have some fat on me.. So am I right? Am I being sabotaged?? My home is a smoke free home btw an I don’t hang with anyone who smokes weed!! I need some answers before I lose my mind lol

    • Prof of Pot says:

      It does seem suspicious. It would be possible to come back at the same metabolite level two times in a row. Even though metabolite levels are always dropping on average once you quit smoking, there is a ton of variability from sample to sample, depending on hydration and other factors. So it is possible to measure the same metabolite level 2 times in a row, but the chances of it coming in at exactly the same level for 3 times in a row is incredibly unlikely. Plus, you should come up clear by 70+ days. Do you know which lab carried out the testing? It would be difficult to sabotage the sample if they are a legit lab. False positives are possible, although very rare if they are using GC/MS. Maybe you can explain to your employer that there must be an error in the test for it to come back at the exact same metabolite level 3 times.

  10. Lou says:

    Great article! If we use a smaller dose (5g/day) can we take the charcoal more frequent than 2 days on/5 days off?

    • Prof of Pot says:

      Sure, some people take small amounts every day because they believe it is detoxifying (I don’t mean specifically for THC metabolites, but just in general). 5 g is still a pretty big amount though. You may end up with some constipation. But if you do start getting any side effects, then just stop taking the charcoal. You can also take fiber on days you don’t take the charcoal.

  11. Jody says:

    Hi Doc! Is there a benefit to taking charcoal every day preceding a drug test, or is it overkill? Let’s say for example you have a week before a drug test. Would it make sense to take charcoal every day (minus the potential for constipation?), or do you think there’s a “cutoff” for how much is helpful/clearing?


    • Prof of Pot says:

      The more days you take it, the faster it will clear. Fiber also helps (although it is not as efficient as the activated charcoal). If you only have a week, you could try it every day. There is a cutoff for how much you take at a time though – at a certain point you are taking more than is necessary to bind all of the metabolite that is released in the bile.

  12. Brian says:

    Hi Doc.
    I’ve always suspected that AC does remove metabalites and with other toxins.

    You see on the internet about all the na Sayers. But you mentioned Entropathic Circulation. Along with that process a lot of people fail to think and lack basic biology. Inside the small intestines are villis and micro villies.

    Those micro villies contain small blood vessels. They are usually one cell thick. So do you think along with E. Circulation it’s possible for the blood being cleaned directly through the small intestine? Since AC has a +/- attraction to molecules. It would be easy for molecules with +/- to travel through single cells.

    I take AC periodically to help with gas and bloat. But since I’ve seen the article. I’ve tryed and experiment on myself.

    I smoke and drink beer daily. Usually about .5 gram of high grade and usually 2 4 packs.

    The last couple weeks I’ve taking 2 capsules of AC in the morning before I go to work. A total of 560mg or 5.6 grams. I started at the end of July.

    One thing I’ve noticed is does appear to be some truth with this article. I’ve noticed my tolerance to both beer and weed has dropped. So I guess that it’s giving me a T-break.

    I’m going to continue taking AC. May order test strips next week.

    Also I’ve seen other web pages that filtering urine directly through AC cleans it too.

    • Prof of Pot says:

      There is a specific name for what you are describing – it is called exsorption (it is like the opposite of absorption). I couldn’t find any studies on whether significant exsorption happens with THC or its metabolites. It is possible, so I wouldn’t rule it out.

      Filtering the urine through AC should work too, although I wonder whether it would also discolor it or remove creatinine, which could cause sample rejection. I haven’t read about this technique yet, so thanks for mentioning it.

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