What the evidence says. Graded preliminary: a single fMRI RCT showed a 7% memory-retrieval gain and two small psychiatry RCTs supported fear-extinction learning, but the large phase-3 Alzheimer's trial of the derivative LMTM failed its primary endpoints. The mechanism is real but durable cognitive benefit in healthy people is unproven. (Preliminary evidence: Early or small human trials; promising but not yet conclusive.)
What is Methylene Blue?
Methylene Blue (Methylthioninium chloride) is a nootropic used for possible short-term memory boost. NutriDex grades the human evidence as Preliminary. Methylene blue is a century-old synthetic dye used medically to treat methemoglobinemia and now marketed as a nootropic and 'longevity' aid. The strongest human signal is a randomized fMRI study in 26 healthy adults where a single low oral dose raised brain activity during attention and memory tasks and produced a 7% increase in correct memory-retrieval responses. Two small psychiatry RCTs found it can enhance retention of fear-extinction (exposure therapy) when learning succeeds. However, the large 891-patient phase-3 trial of its reduced derivative LMTM in Alzheimer's disease failed both primary cognitive and functional endpoints, with benefit seen only in an unplanned monotherapy subgroup. At low doses it supports mitochondrial electron transport, but evidence for lasting cognitive enhancement or extended lifespan in humans is absent. Effects are acute and dose-dependent — higher doses impair, not help.
Purported Benefits
✓Possible short-term memory boost
✓Mitochondrial energy support
✓Aids fear-extinction learning
✓Treats methemoglobinemia (medical use)
Evidence by outcome
The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.
Outcome
Evidence
Effect
Studies
Acute short-term memory boostSingle low-dose fMRI RCT (n=26) gave a 7% rise in correct memory retrieval; acute, one small trial.
Methylene blue is a potent reversible MAO-A inhibitor and carries an FDA boxed warning for potentially fatal serotonin syndrome when combined with SSRIs, SNRIs, MAOIs, bupropion, triptans, tramadol or other serotonergic drugs — avoid these for at least 2 weeks before and 24–72 hours after. It is contraindicated in G6PD deficiency (causes hemolytic anemia) and should be avoided in pregnancy. High doses paradoxically cause methemoglobinemia, blue-green urine/skin, nausea, headache and can raise blood pressure; it may also interact with other MAO-affecting drugs. It is a prescription drug, not a dietary supplement, and unregulated 'pharma-grade' products vary in purity. Educational only — always check with your doctor or pharmacist before combining Methylene Blue with any medicine.
Methylene Blue is most often taken for Possible short-term memory boost, Mitochondrial energy support, Aids fear-extinction learning, Treats methemoglobinemia (medical use). Old dye, hyped as a brain booster — human data are thin.
Does Methylene Blue work — what does the evidence say?
Preliminary evidence. Early or small human trials; promising but not yet conclusive. Methylene blue is a century-old synthetic dye used medically to treat methemoglobinemia and now marketed as a nootropic and 'longevity' aid. The strongest human signal is a randomized fMRI study in 26 healthy adults where a single low oral dose raised brain activity during attention and memory tasks and produced a 7% increase in correct memory-retrieval responses. Two small psychiatry RCTs found it can enhance retention of fear-extinction (exposure therapy) when learning succeeds. However, the large 891-patient phase-3 trial of its reduced derivative LMTM in Alzheimer's disease failed both primary cognitive and functional endpoints, with benefit seen only in an unplanned monotherapy subgroup. At low doses it supports mitochondrial electron transport, but evidence for lasting cognitive enhancement or extended lifespan in humans is absent. Effects are acute and dose-dependent — higher doses impair, not help.
What is the typical dose of Methylene Blue?
Nootropic research uses single low oral doses (~0.5–4 mg/kg, often ~280 mg); there is no established supplement regimen, and high doses are toxic.
Is Methylene Blue safe? Any cautions or side effects?
Methylene blue is a potent reversible MAO-A inhibitor and carries an FDA boxed warning for potentially fatal serotonin syndrome when combined with SSRIs, SNRIs, MAOIs, bupropion, triptans, tramadol or other serotonergic drugs — avoid these for at least 2 weeks before and 24–72 hours after. It is contraindicated in G6PD deficiency (causes hemolytic anemia) and should be avoided in pregnancy. High doses paradoxically cause methemoglobinemia, blue-green urine/skin, nausea, headache and can raise blood pressure; it may also interact with other MAO-affecting drugs. It is a prescription drug, not a dietary supplement, and unregulated 'pharma-grade' products vary in purity.
How many studies support Methylene Blue?
NutriDex cites 7 sources for Methylene Blue, graded "Preliminary".
Cite this page
APA
Peh, D. (2026). Methylene Blue (Methylthioninium chloride): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 16 Sept 2026, from https://nutridex.info/s/methylene-blue
BibTeX
@misc{nutridex_methylene_blue,
author = {Peh, Daryl},
title = {Methylene Blue (Methylthioninium chloride): Benefits, Dosage, Side Effects \& Evidence},
year = {2026},
howpublished = {NutriDex --- The Supplement Research Compendium},
url = {https://nutridex.info/s/methylene-blue},
note = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-09-16}
}
For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.