Wellness enthusiasts seeking to hack their way to health and longevity have a new favorite remedy — one that stains their tongues blue.
Methylene blue has been around since the 1870s when it was used as a textile dye. Since then it's been prescribed as an antimalarial treatment and an antidote for cyanide poisoning. Today it's medication approved by the U.S. Food and Drug Administration as treatment for methemoglobinemia, a rare blood disorder.
But online influencers are promoting it for what they claim are its wellness properties. It's taking off among biohackers, who seek to optimize their health via lifestyle changes.
Commentators speculated that Robert F. Kennedy Jr. takes methylene blue after a video of the nation's top health official circulated early this year. He can be seen using an eyedropper to mix a cobalt blue liquid into a cup of water. Kennedy never confirmed what he was taking, though the vibrant color and applicator resembles the methylene blue products that are sold by online retailers. And Kennedy's known for taking supplements, and has a track record of embracing debunked or unproven scientific claims.
The Claim:
Methylene blue improves the function of mitochondria — components of our cells which convert nutrients into energy — and that results in a host of benefits, such as slowed aging, better mood and sharper cognition. Some even claim it alleviates jetlag.
The Evidence:
Lab studies and animal trials have found that methylene blue can help cells make energy more efficiently by giving mitochondria an easier way to move electrons when their normal pathways are damaged or stressed, says Lorne Hofseth, who studies dyes' effect on cancer and inflammation at the University of South Carolina College of Pharmacy.
He also cites studies done in rodents and worms to show that methylene blue improves brain energy use, reduces inflammation, and protects against neurological damage.
When it comes to research in humans, there have been several smaller trials in select populations that have shown antidepressant or cognitive benefits from pure methylene blue. But Hofseth says these findings remain preliminary — which is why he strongly discourages people from taking it as a supplement, as right now, the risks outweigh the benefits.
"You're wasting your money," he says.
That doesn't mean methylene blue is a total scientific dead end. Hofseth points to promising work being done in the UK on a modified form of the dye to treat Alzheimer's disease. But this methylene blue is different from the dye people are purchasing as an over the counter supplement.
So why might online influencers feel convinced that methylene blue makes them feel better and think faster?
"Cognition is subjective," says Nicole Brandt, a professor at the University of Maryland School of Pharmacy who studies geriatric pharmacotherapy. "We have good and bad days if we sleep well, if we eat well."
The Risks:
In addition to wasting money, Hofseth and Brandt both warn of adverse side effects from methylene blue. That includes serotonin toxicity, which is a serious drug reaction, which can cause elevated blood pressure, diarrhea, seizures, and even death: People who take certain antidepressants, including Zoloft and Lexapro, are especially at risk.
Methylene blue could also be dangerous for people who have a genetic disorder affecting red blood cells called glucose-6-phosphate dehydrogenase deficiency.
Another concern is people may not know what they're getting when they buy methylene blue over the counter.
"We really don't have good oversight, or any oversight to nutritional supplements and what's in them," Brandt says.
Unlike drugs, supplements are not approved by the FDA for safety and efficacy before they go on the market. But they do have to follow certain rules around labeling. Manufacturers are also subject to inspection, and the FDA monitors safety concerns once products are on the market.
However, federal regulators have finite resources and are unable to catch every bad actor, says Dr. Joshua Sharfstein, a professor at Johns Hopkins Bloomberg School of Public Health and a former principal deputy commissioner at the FDA. That's why he says it's buyer beware with methylene blue, and similar products
"The internet is a big place," he told NPR. "There are a lot of products for sale that are not safe."
It's also not clear whether methylene blue meets the regulatory definition of a supplement. It's listed in an FDA database as a generic drug that requires a prescription.
And most methylene blue products are not in a federal registry of dietary supplement labels, according to Jeff Ventura, vice president for communications at the Council for Responsible Nutrition. Many of the products seen online are not explicitly identified as supplements.
The FDA did not respond to a request for comment about how it's possible for online retailers to sell methylene blue without a prescription.
The Bottom Line:
Those who still want to try methylene blue should first talk to a clinician to ensure they're not at risk for adverse side effects. And if someone's taking methylene blue for a specific health concern, like brain fog or fatigue, a primary care provider can also help address those issues, says Sharfstein.
If you do decide to try the product, be warned: It could turn your teeth, tongue and urine bright blue.
Copyright 2025 NPR