Study: Most marijuana edibles have mislabeled potency

Researchers from Johns Hopkins University did a study to see if the amount of THC in edible marijuana products was the same as the amount specified on the labels. The answer was a resounding “nah, man.”

Hopkins scientists went to Colorado and Washington state, where recreational marijuana is legal, and bought a total of 75 different edible products containing marijuana. They then tested the products’ THC content to see if it matched the amount of THC that was promised on their labels.

Marijuana edibles, via Wikimedia Commons

Marijuana edibles, via Wikimedia Commons

They found that over three three quarters of the edibles did not contain the specified amount of THC, with 60 percent of edibles tested containing less THC than advertised. 23 percent of the products actually contained more THC than was claimed on the label.

The researchers state that edibles containing marijuana cannot be relied upon to give a medicinal dose to patients taking it. One researcher said, “I suspected that we would see variability, but I was shocked at how much variability there was.”

One reason may be that both states require in-state testing of THC content by local labs. These labs, and labs in general, don’t have much experience in testing for THC in substances other than serum and urine. And testing for THC in marijuana plants and oils is more straightforward than trying to test for marijuana in, say, a brownie, where there are a number of other ingredients present.

For pharmaceuticals prescribed in the U.S., the Food and Drug Administration requires strict testing on drugs produced, including medications like PrEP and aspirin. But since the FDA states that marijuana is a non-medicinal drug, it has nothing to do with determining the purity or amount to THC in any marijuana products.

Another reason for the mislabeling is that the producers of medical marijuana edibles are mostly small mom and pop stores. They may not have the knowledge or skills to prepare brownies, cookies and other edibles properly or consistently. Recipes differ and how the THC is added to the mixture varies. Of course, there is also the possibility that there may be some producers who are just shortchanging the consumer to increase their own profits.

For right now at least, if you or someone you know is using medical marijuana and expecting a consistent dose, it may be much better to use it in a non-edible form.  Perhaps, over time the analytical techniques will get better, or the FDA will step in, and the THC content of edibles will be more accurate.


Mark Thoma, MD, is a physician who did his residency in internal medicine. Mark has a long history of social activism, and was an early technogeek, and science junkie, after evolving through his nerd phase. Favorite quote: “The most exciting phrase to hear in science... is not 'Eureka!' (I found it!) but 'That's funny.'” - Isaac Asimov

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  • FLL

    Combustion (burning) is the hardest on your lungs, and includes some by-products of burning that you can do without. Vaping is better, but some people have sensitive bronchial tubes (and a tendency to have bouts of bronchitis or asthma), in which case edibles are always best. Soy lecithin is a fun addition during the heating stage of edible making because it increases bioavailability.

  • LOL! Guess nobody told her about the need for the ‘magic butter’ recipe to start with.

  • SkippyFlipjack

    I had brownies at a party once that weren’t strong, they were tough. As in, the hostess had just dumped a bunch of weed in the batter. It was like eating a shrub dipped in cake :)

  • Fair enough.

  • True enough. I remember once eating a brownie…and it turned out not to be as mild as I’d hoped. I do agree that particularly for medical and not recreational use, they need to get a handle on standardized dosing.

  • SkippyFlipjack

    See the risks? Jasmine has clearly had too strong a dose of THC.

  • SkippyFlipjack

    You’re absolutely right. I was just surprised to see the thoughts that “too much is a good thing” or “at least and OD won’t kill you” or “it’s no different than physician-prescribed pills made in China”. those seemed like things people would say if the only edibles available were brownies the neighbors made.

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  • SkippyFlipjack

    It just seemed sort of flip — no, an overdose won’t kill you, but it can really really suck. When we’re talking about MJ as medicine, that’s just a terrible metric, right? Like if Valium said on the package “Actual product dosage may vary, but won’t kill you.” I’d find that sort of distressing.

  • Indigo

    That’s one of those dosage issues that will be resolved as medical marijuana becomes better recognized as a valid use of canabis. Meanwhile, experimentation by rule of thumb and the confidence that even if a dosage is higher than usual, nobody’s going to experience SDS [sudden death syndrome] the way the pharmaceuticals advertised on television warn.

  • No, he’s not.

  • I’m wondering if anyone commenting below has any experience with edibles.

    Wonder no more.

  • That’s not what I said or meant at all.

  • Mike_in_the_Tundra

    I can certainly agree with that.

  • SkippyFlipjack

    You’re the exception. :)

  • SkippyFlipjack

    Right, which is exactly why edibles need to be of predictable doses. I mainly was objecting to the idea that ‘more thc is better’ or that consistency doesn’t really matter.

  • Mike_in_the_Tundra

    Many people taking medical marijuana have compromised respiratory systems. They are unable to smoke their medicine. They can’t vape it either.

  • SkippyFlipjack

    That’s true, but I just meant the article wasn’t really proof of your conclusion. It only spoke to the potency of edibles. It’s probably proof that if you want your edibles consistent you make them yourself out of lab-tested herb or home-grown.

  • Knottwhole

    Well lets see…….If I know what my herb consists of, you know, the things like thc and cbd, I can make a great guess on how much of the active ingredients are in the cookies and candies I make. Good enough for ya?
    Please try to not be so condescending towards others.

  • Knottwhole

    Duh. The point being, if you grow your own, you can control your medibles.
    Can’t have medibles without herb.

  • SkippyFlipjack

    This is about edibles, not herb.

  • SkippyFlipjack

    OK, sure, if that’s your baseline by which you measure the effectiveness of a drug.

  • SkippyFlipjack

    I’m wondering if anyone commenting below has any experience with edibles. You absolutely do want to know how strong the edibles are. Maybe you don’t care that much if you just want to go to a concert and get f*cked up, but since a big part of the MJ movement is about the medical benefits, it needs to be treated like medicine and be available in consistent doses. Edibles aren’t like smoking where you know pretty quickly how strong it is and can meter the dose accordingly.

    At this point I think people still need to consider edibles as party drugs. When taking Advil you don’t have to decide between a cupcake and a gummy bear.

  • UncleBucky

    I would like to be able to know the potency, eh? Of course, if a producer has a consistent quality they can demonstrate, that would probably be all right for the moment.

    Right now, I’m off it since 1973. :P

  • devlzadvocate

    I’d kinda like to know which products were tested in the 23% that tested too high. As Martha Stewart says, “It’s a good thing”.

  • Yeah, but y’know, here’s the thing: Even if you ingest more than you were expecting, the THC overdose won’t kill you.

  • Knottwhole

    Just further proof, that if you want it consistent, you need to grow your own.

  • nicho

    So, basically, not much different than the crap your MD prescribes for you and which comes from “laboratories” in China, which are somewhat akin to barns.

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