Methylene blue, a synthetic dye first made in the 1870s and a legitimate hospital treatment for methemoglobinemia, has gone viral as a longevity and nootropic supplement. It has accumulated thousands of TikTok posts, with users filming their blue-stained tongues and crediting it for mood, focus, energy and 'mitochondrial' benefits. The trend has been amplified by high-profile figures: biohacker Bryan Johnson announced starting it in 2025, Mel Gibson discussed it on a podcast, and a widely shared video appeared to show RFK Jr. dosing a blue liquid.
The claims outrun the science. There are no clinical studies demonstrating that methylene blue improves memory, cognition, longevity, sleep, skin aging or energy in humans. The frequently cited Alzheimer's findings exist only at the laboratory and test-tube level, with no demonstrated benefit in human clinical trials. Chemists also note that the marketed oxidized form is not the antioxidant form proponents describe.
The safety issue is concrete rather than theoretical. Methylene blue inhibits monoamine oxidase, and combining it with SSRIs or other serotonergic drugs can trigger serotonin syndrome — agitation, rapid heartbeat, hallucinations and loss of muscle coordination. With roughly 13% of Americans on SSRIs, clinicians warn that anyone taking these medications should avoid it. Other effects range from harmless blue urine to nausea, diarrhea and, at higher doses, methemoglobinemia risk itself.
The reality: methylene blue is a real drug with a narrow legitimate use, being repurposed on the basis of preclinical signals and celebrity endorsement. The cognitive and anti-aging claims are unconfirmed in humans, and the SSRI interaction makes casual self-dosing genuinely hazardous for a large slice of the audience it's marketed to.