Methylene Blue
Methylene blue (methylthioninium chloride)
Also known as: MB, Methylthioninium chloride, ProvayBlue
An FDA-approved antidote for methemoglobinemia that biohackers take at low doses for mitochondrial energy and focus; the cognitive evidence is thin and it is a monoamine oxidase inhibitor with documented fatal interactions with antidepressants.
Overview
Methylene blue is a century-old dye and drug. At low doses it can act as an alternative electron carrier in mitochondria, and small imaging studies in healthy adults showed changes in brain activity during memory tasks. Its derivative, hydromethylthionine, failed to produce clean Phase 3 results in Alzheimer's disease. A wave of interest in 2026 followed public figures being seen drinking it. It is a potent MAO-A inhibitor at doses well under 1 mg/kg, and at least 14 published cases of serotonin syndrome, including a death, have occurred in people also taking SSRIs, SNRIs or other serotonergic drugs. G6PD deficiency is a contraindication. Products sold as supplements or aquarium-grade dye are not pharmaceutical grade.
Mechanism of action
Redox cycling that shuttles electrons within the mitochondrial respiratory chain, plus reversible inhibition of monoamine oxidase A and nitric-oxide synthase.
Key studies & citations
- Human2016
Multimodal randomized functional MR imaging of the effects of methylene blue in the human brain
A single low dose altered task-related brain activity in 26 healthy adults.
Radiology - Human2017
Methylene blue modulates functional connectivity in the human brain
Connectivity changes; no clinical cognitive outcome.
Brain Imaging and Behavior - Human2010
Serotonin syndrome from methylene blue with serotonergic drugs
Case series establishing the MAO-inhibitor interaction.
Psychosomatics - Review2018
Methylene blue-associated serotonin toxicity: updated review
At least 14 cases including a fatality.
Psychosomatics
Frequently asked questions
Can I take methylene blue with an SSRI?
No. It inhibits monoamine oxidase and has caused serotonin syndrome, including a death, when combined with SSRIs, SNRIs and related drugs. This is the most important fact about it.
Does it improve memory?
Small imaging studies show brain-activity changes after a single dose. No trial shows a meaningful cognitive benefit in healthy people, and the related Alzheimer's drug failed.