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Methylene blue

MB · Mitochondrial agent (nootropic use)

Research reference only. Pepdex does not sell, supply or track this compound, and nothing here is guidance to use it — this page exists so the evidence and the risks are visible.

What it is

A century-old dye and antidote drug (methemoglobinemia) that biohackers adopted as a mitochondrial enhancer — at low doses it can act as an electron shuttle in the respiratory chain. Turns urine blue-green, which is the most reliably reproduced effect it has.

How it works

Methylene blue is an old synthetic dye that turned out to be a drug — one of the first, and still a hospital medicine. Its established use is treating methaemoglobinaemia, where iron in haemoglobin is stuck in a form that cannot bind oxygen normally and also impairs delivery by the haemoglobin that still works; methylene blue's reduced metabolite converts that iron back. The nootropic interest rests on a separate property described in laboratory and animal work: at low concentrations it accepts and donates electrons in the mitochondrial respiratory chain, with the behaviour reversing to pro-oxidant at higher ones. That is a preclinical hypothesis, not established human pharmacology — FDA states the exposure-response relationship is unknown, and no beneficial nootropic exposure has been established from it.

What human evidence shows

Legitimate medical uses are established. The cognitive story rests on small studies (one fMRI memory task paper does heavy lifting in every thread about it) and on hormetic mouse data showing low-dose benefit that INVERTS at higher doses. No solid human trials for memory, energy or longevity endpoints.

The studies, one by one

  • Solidly established as a hospital treatment for methaemoglobinaemia, given intravenously under supervision. That is the evidence base, and it is about a specific emergency.
  • For cognition, memory or mood in healthy people there is very little: a small number of small imaging and behavioural studies, nothing approaching an outcome trial.
  • The Alzheimer's trials used LMTM (hydromethylthionine), a reduced methylthioninium formulation, in an 891-participant phase III study — and the prespecified co-primary cognition and daily-function analyses were negative in add-on use.
  • Serotonin syndrome is the best-documented serious harm, and it is not theoretical — methylene blue is a potent MAO inhibitor, and cases have occurred in patients taking serotonergic antidepressants who were given it in hospital. This prompted formal regulatory safety communication.
  • Haemolysis in people with G6PD deficiency is a recognised and potentially severe reaction.

Half-life and how long it lasts

Half-life in the range of half a day to a day. It is a potent monoamine oxidase inhibitor, which is the single most important pharmacological fact about it and the source of its worst interaction. It turns urine and sometimes stool blue-green, which is harmless and universal. Aquarium-grade and laboratory-grade product is not pharmaceutical grade and may carry contaminants including heavy metals — a real distinction, since much of what is sold for self-experimentation is not made for human use.

Risks

It is an MAO inhibitor — combined with SSRIs/SNRIs or other serotonergics it can cause serotonin syndrome, which is a hospital problem, not a headache. The dose-response is a U-curve, so the enthusiast logic of taking more inverts the effect. G6PD deficiency is a contraindication. Aquarium-grade product is not a human-grade product.

Who should never touch it

  • Anyone taking any serotonergic antidepressant or other serotonergic drug — this is the absolute one
  • Anyone with G6PD deficiency
  • Anyone pregnant or breastfeeding
  • Anyone with severe kidney impairment
  • Anyone using non-pharmaceutical-grade product

Interactions worth knowing

  • Serotonergic drugs — the serious one, with documented serotonin syndrome and a formal regulatory warning behind it. The label list is wider than most people expect: SSRIs, SNRIs, tricyclics, MAO inhibitors, triptans, tramadol, lithium, and also opioids, dextromethorphan, buspirone, bupropion, mirtazapine, clomipramine and linezolid. The documented cases involved IV methylene blue; FDA calls the risk from oral routes unclear, which is not the same as absent.
  • G6PD deficiency, where it can cause severe haemolysis.
  • Enzyme-inhibition effects seen in the laboratory did not materially change drug exposure in the label's clinical interaction study, so treat claimed interactions beyond the serotonergic list as uncertain rather than established.

Stacking interactions

Documented interactions with other things people research. A compound not listed here does not mean the combination is safe — only that no specific interaction is on file.

AvoidTesofensine

Combining agents that raise serotonergic tone is the classic route to serotonin syndrome, a medical emergency.

What a clinician would watch

  • Any serotonergic medication you take — this is the check that matters most, and it should happen before rather than during.
  • G6PD status, since deficiency turns this into a haemolysis risk — and G6PD is not the only serious issue: the label carries anaphylaxis, delayed haemolytic anaemia, fetal harm, an eight-day breastfeeding interruption, phototoxicity, impaired driving from confusion and visual effects, interference with pulse oximetry readings, and markedly higher exposure in kidney impairment.
  • Symptoms of serotonin syndrome: agitation, tremor, sweating, rapid heartbeat, confusion, muscle rigidity. This is an emergency, not a side effect to sleep off.
  • Product grade — pharmaceutical versus aquarium or laboratory supply.

What stopping looks like

No withdrawal syndrome. The blue-green urine clears within a day or two. Anyone who experienced symptoms suggesting serotonin syndrome needs urgent medical assessment rather than simply stopping, and should tell the clinician that methylene blue is an MAO inhibitor, because that changes management and is not something every clinician has front of mind.

Myth vs evidence

“It is a safe nootropic because it is an old approved drug.”

It is approved for an emergency blood condition given under supervision. Its MAO inhibition makes it genuinely dangerous alongside common antidepressants.

“Aquarium methylene blue is the same chemical.”

The molecule may be, the product is not. Non-pharmaceutical grades can carry contaminants including heavy metals and are not made for human consumption.

“More is more mitochondrial support.”

In laboratory work the electron-carrier effect is confined to low concentrations and reverses to pro-oxidant at higher ones — and even that low-dose benefit is a preclinical hypothesis, not established human pharmacology.

“The Alzheimer's trials showed it works.”

Those trials used a related compound and the large programme missed its primary endpoints.

Legal status

US: prescription drug for its medical indications; sold grey-market as "research" liquid. Not scheduled.

Research on this compound

Papers about this compound, not proof of the claims above. A title says what was studied, which is sometimes a negative result or a different question entirely.

Evidence base

S30,316 research papers
established literature

Large human evidence base: several phase 3 or 4 trial reports, plus multiple meta-analyses or systematic reviews.

phase 3/4
8
randomised
448
reviews
129
human trials
612

Counts are of published papers, not distinct trials, and they nest rather than add up: PubMed files every randomised trial as a clinical trial too. They measure how much research exists — not whether this works or is safe for you.

Research (12)

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Where next

Every compound in the catalogThe full non-peptide index, with evidence grades.→The peptide indexInjectable peptides, half-lives and what trials used.→Spotting a scam vendorRed flags, COA checks and what traceability looks like.→