What Doctors Need to Know About the Activated Charcoal Trend

Dana G. Smith


July 17, 2019

Activated charcoal has been a mainstay in poison treatment for decades due to its effectiveness at adsorbing chemicals and drugs following an overdose. In recent years, this legitimate medical use has been co-opted as an antidote for all that ails. Activated charcoal has popped up in juices, toothpaste, and face washes, ostensibly to "detoxify" the body. These products probably have little effect—for good or for bad. More concerning are the activated charcoal capsules available in pharmacies and health food stores that claim to aid intestinal cleansing and help with gas and bloating; these supplements could be doing more harm than good.

In the stomach, activated charcoal soaks up most of the molecules it comes into contact with, preventing them from being absorbed into the bloodstream. The material's sponge-like quality stems from its many pores, which give it an enormous surface area to bind to other substances. Once the chemicals adhere to the charcoal in the gastrointestinal tract, they can safely pass through the body.

Activated charcoal supplements found in most drugstores promise to relieve intestinal gas, but medical experts question whether they work. "The number-one thing is, is it useful?" asks Jacqueline Wolf, MD, a gastroenterologist at Beth Israel Deaconess Medical Center in Boston. "The studies are contradictory on its use for gas and bloating, which is what a lot of people are using it for."

The few studies on activated charcoal's ability to adsorb gas in the gut—most dating from the 1980s—are mixed. Two papers report that activated charcoal significantly reduced gas production, measured by breath hydrogen levels and flatus events.[1,2] However, other studies found that activated charcoal did not affect fecal gas release, the number of times someone passed gas, or breath hydrogen concentration after a meal.[3,4]

The other primary consideration, Wolf says, is activated charcoal's side effects. "Besides getting a dark tongue and dark roof of the mouth, one of the major problems with activated charcoal is that it causes nausea and vomiting in a large percentage of people."

By some estimates, 20%-30% of people vomit after taking activated charcoal for poisonings.[5] Less common but not unheard of are gastrointestinal obstruction or fecal impaction. There have also been reports of regular activated charcoal consumption causing chronic intestinal problems. In one case study from 2014, a man developed colitis 4 days after he began taking charcoal for fatigue.

Ironically, activated charcoal may be ineffective at two of its most widely advertised uses: adsorbing alcohol and heavy metals.[6,7] Alcohol is absorbed too quickly into the bloodstream for the charcoal to make much difference, whereas metals and charcoal have a weak chemical bond.[8] "A lot of people don't really understand what they're trying to detox from," says Kristen Smith, MS, RDN, LD, a spokesperson for the Academy of Nutrition and Dietetics.

While its ability to adsorb certain unwanted toxins and intestinal gas is dubious, activated charcoal really can soak up prescription and over-the-counter medications. Known interactions include painkillers, antidepressants, arthritis drugs, diabetes medications, oral contraceptives, antiarrhythmics, beta-blockers, antiepileptics, and bronchodilators. Another concern is that activated charcoal could inadvertently bind to and prevent the absorption of important vitamins and nutrients.[9]

"It's about dose and it's about timing of the charcoal administration," says Christopher Holstege, MD, a professor of emergency medicine at the University of Virginia and director of the Blue Ridge Poison Center. "If you're taking it around the time that you're taking the medication, there is a potential for binding some of that up and causing problems.... If [the dose] is really small and you're taking it hours before you're taking the medication, or after you take the medication, it may not have any effect at all."

The conventional wisdom is that you need 10 times more charcoal than the substance you're trying to adsorb. In the hospital, activated charcoal is given in liquid doses of 50 g, whereas over-the-counter supplements are typically sold in 500-mg capsules. According to one study, 50 g of activated charcoal reduced drug absorption by an average of 47% when given within 30 minutes, with that rate dropping over time to about 21% at 180 minutes.[10] It is feasible, then, that a charcoal supplement consumed within an hour of an oral medication dosed at 50 mg or less could interfere with the absorption of the drug.

"Because the surface area is just so huge, even if there are weak interactions, things can be bound to the charcoal," says David Kroll, PhD, a professor in the department of pharmaceutical sciences at the University of Colorado Denver. "Any drug that's taken at a relatively low dose, I could see these charcoal capsules having a deleterious effect."

None of the experts interviewed for this article had encountered a case of a charcoal–medication interaction, but some were still wary of the potential risk. "Do I think we'll find reports of complications with this? Yes," Holstege says. "There are always extremes where people think a little is good so more is better: 'I'm going to take a lot more charcoal to try to detoxify myself' or for whatever reason I'm taking it. That will then start to bind up medications and has the potential to cause intestinal obstructions and other problems."

Wolf, on the other hand, said that while she was unconvinced of charcoal's efficacy, she thought the risk of side effects was minimal. "I don't think if someone's taking a small amount of it before a meal that it's going to hurt," she says. "They may just be wasting their money."

Follow Medscape on Facebook, Twitter, Instagram, and YouTube


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.