Know2eat

Methylene blue

Isolated Compounds

What methylene blue may help with

Ranked by how strong the human evidence is — best supported first.

Best supportedCognitive functionNot enough evidence· 3 sources

Then, in order

About Methylene blue

A synthetic thiazine dye and the first fully synthetic drug used in medicine, approved for treating methaemoglobinaemia. It has become a self-administered supplement for cognitive and mitochondrial claims.

Methylene blue is a genuine pharmaceutical with a genuine approved use — reversing methaemoglobinaemia, where it is given intravenously in hospital — and a redox chemistry that makes it interesting to mitochondrial researchers. It is being sold and self-dosed as a nootropic on the basis of animal work and small imaging studies, and the safety profile is the reason to take this seriously rather than lightly. Methylene blue is a potent monoamine oxidase inhibitor, and combining it with serotonergic drugs has caused serotonin syndrome severe enough for drug regulators to issue formal warnings. In people with glucose-6-phosphate dehydrogenase deficiency it causes haemolysis rather than helping. And much of what is sold online is aquarium or laboratory grade, with contaminants that pharmaceutical grade material does not carry.

Sold as
Pharmaceutical grade solution (prescription), Oral drops sold as supplement, Tablets, Aquarium and laboratory grade product used off-label
Standardised to
Pharmaceutical or USP grade is the meaningful distinction; industrial and aquarium grades carry heavy metal and dye contaminants — a product without this marker may not resemble what was studied.
Also known as
Methylthioninium chloride, Provayblue, USP methylene blue

Regulation: An approved prescription medicine for methaemoglobinaemia, given intravenously under supervision. It is not an approved dietary supplement, and drug regulators have issued formal safety communications about serotonin syndrome when it is combined with serotonergic medicines. Products sold for self-administration sit outside both frameworks.

What the research used

The amounts, forms and durations published trials of Methylene blue actually administered.

These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.

  • Studied for Approved medical use

    1–2 mg

    Strong

    Per kilogram of body weight, intravenously, for methaemoglobinaemia

    The approved hospital use, given by clinicians with monitoring. It has no bearing on oral self-administration.

  • Studied for Small cognitive and imaging studies

    0.5–4 mg

    Not enough

    Per kilogram, oral, single dose in experimental settings

    Doses in small experimental studies measuring brain imaging changes and memory. These are exploratory studies in tens of participants, not evidence of benefit.

This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.

When it was taken

Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.

None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.

  • Any time

    Not enough

    No timing research exists for self-administered use. The dose-response is notably non-linear — it is a redox agent that behaves as an antioxidant at low concentrations and a pro-oxidant at higher ones — which makes casual dose escalation a bad idea.

    Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.

The evidence in depth

Best supported: Not enough

What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.

Cognitive function

Brain & Cognitive Health
Not enough evidence

Small imaging studies report changes in brain activity and modest memory effects after single doses. These are exploratory, in small numbers of people, with no replication and no long-term data.

What may be going on: Methylene blue can act as an alternative electron carrier in the mitochondrial respiratory chain, and inhibits monoamine oxidase and nitric oxide synthase.

Not enough evidence. Not enough human research to say anything useful yet.

View the 3 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Energy metabolism

Energy & Metabolism
Not enough evidence

The mitochondrial electron-carrier mechanism is real in laboratory systems. No human trial has demonstrated a benefit for energy or fatigue.

Not enough evidence. Not enough human research to say anything useful yet.

View the 4 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Things to know

Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.

  • Interaction

    A monoamine oxidase inhibitor — serotonin syndrome risk

    Interacts withSSRIs, SNRIs, tricyclic antidepressants, MAO inhibitors, triptans, tramadol, lithium

    Methylene blue is a potent MAO inhibitor, and combining it with SSRIs, SNRIs, tricyclics, triptans, tramadol, lithium or MAOI antidepressants can cause serotonin syndrome — confusion, agitation, fever, rigidity, seizures and death. Drug regulators have issued formal safety communications on exactly this. Given how many people take an antidepressant, this is the single most important fact about it.

  • Avoid

    Haemolysis in G6PD deficiency

    In people with glucose-6-phosphate dehydrogenase deficiency, methylene blue causes destruction of red blood cells rather than the intended effect, and can be dangerous. G6PD deficiency is common in parts of Africa, the Mediterranean, the Middle East and South East Asia, and many people carrying it do not know.

  • Worth knowing

    Product grade matters enormously

    Much of what is sold online is aquarium or industrial grade dye, which can contain heavy metals and other contaminants at levels unacceptable for ingestion. Pharmaceutical or USP grade is the only material with any purity assurance, and it is a prescription product.

  • Too much

    Dose-dependent toxicity and blue discoloration

    Blue or green urine and a blue tint to the skin, tongue and sclera are expected. Higher doses cause nausea, abdominal pain, chest pain, dizziness, confusion and, in overdose, methaemoglobinaemia — the very condition it is given in hospital to correct. The dose-response is biphasic, so more is not simply more.

  • Avoid

    Not in pregnancy

    Methylene blue has been associated with fetal harm, including intestinal atresia after intra-amniotic use, and should be avoided in pregnancy and breastfeeding.

Evidence ratings on this page: 2 not enough evidence.

Supplements are sold in the US without pre-market review of efficacy or safety. Nothing on this page is a recommendation to take Methylene blue, or a dose to follow.