What is Methylene Blue? History, Uses, and Modern Applications

Written by the NooBlue editorial team. NooBlue makes and sells methylene blue capsules, gummies and drops, so we have a commercial interest in this topic. Every date, dose and study figure below is linked to its source at the end of the page.

What is methylene blue?

Methylene blue is a man-made compound from the phenothiazine family of chemicals. Its formula is C₁₆H₁₈ClN₃S and its molar mass is 319.85 g per mole. It is a salt: the colored part is a positively charged three-ring core with a sulfur atom and a nitrogen atom in the middle ring, balanced by a chloride ion. As a solid it is a dark green powder, and it turns water a deep blue.

It goes by several names. Methylthioninium chloride is the name used for the medicine. Basic Blue 9 and CI 52015 are its dye-industry codes. All of them mean the same molecule.

The detail that explains most of its biology is that methylene blue is a redox dye. Add two electrons and a hydrogen ion and the blue cation becomes leucomethylene blue, which is colorless. Take the electrons away again and it turns blue. The molecule is not used up in the process, so one molecule can pass electrons along many times. Our guide to leucomethylene blue, the colorless form, covers that chemistry in more depth.

Methylene blue does not occur in plants, food or minerals. Every gram sold, whether in a hospital vial, a lab bottle, an aquarium remedy or a supplement, was made in a chemical plant. What separates those products is purity and paperwork, which we come back to below.

Methylene blue vs methyl blue vs methyl red

The names are close enough to cause real mix-ups, including in search results for “methyl blue”.

• Methylene blue is the compound this page is about: a phenothiazine dye, a redox indicator, a hospital medicine and a supplement.
• Methyl blue is a different, much larger dye (formula C₃₇H₂₇N₃Na₂O₉S₃) used in histology to stain collagen blue and in stains such as lactophenol cotton blue for fungi. It is distinctly different in structure, function and use, and it is not a supplement.
• Methyl red is an azo dye used as a pH indicator. It is red below pH 4.4, yellow above pH 6.2 and orange in between. People sometimes search for “methylene red vs blue”, but methyl red has nothing to do with methylene blue beyond the similar name.

If you are buying methylene blue to take by mouth, check that the label says methylene blue or methylthioninium chloride, not methyl blue.

The history of methylene blue

Methylene blue’s history is the history of the first synthetic medicines. The main dates:

• 1876: a new dye. Heinrich Caro, a German chemist in the young synthetic dye industry, first prepared methylene blue.
• 1887: a stain for living nerves. Paul Ehrlich described how methylene blue stains nerve fibers in living tissue. The idea that a dye could pick out one kind of cell and leave others alone helped shape his later thinking about drugs that seek out a target.
• 1891: the first synthetic drug. Paul Guttmann and Paul Ehrlich gave methylene blue to people with malaria in 1891. That is why it is often described as the first fully synthetic drug used in medicine.
• The 20th century: a prototype. Chemists used methylene blue as the lead compound for a series of later drugs, including the antimalarial chloroquine, antihistamines and antipsychotic drugs such as chlorpromazine.
• World War II: blue urine in the ranks. Methylene blue was still given to soldiers as an antimalarial. It was not popular, because it turned their urine blue.
• The late 20th century: a hospital staple. Methylene blue settled into a narrow set of hospital uses, described in the next section, and a large set of laboratory uses.
• The 2000s onward: mitochondria. Researchers returned to the compound because of how it behaves inside mitochondria. A 2008 cell study by Atamna and colleagues found that nanomolar amounts extended the lifespan of human fibroblasts in culture by more than 20 population doublings, and that interest spilled over into the supplement market.

Schirmer and colleagues’ 2011 review in Neurobiology of Aging, titled “Lest we forget you, methylene blue”, covers this history and the compound’s medical record in detail. Our article on methylene blue and parasites goes further into the antimalarial story.

What methylene blue is used for today

Methylene blue has three separate groups of uses, and they should not be confused with each other.

In hospitals

Injectable methylene blue is a prescription medicine. Its main labeled use is acquired methemoglobinemia, a blood condition in which hemoglobin cannot release oxygen properly. StatPearls gives the usual dose as 1 mg per kilogram of body weight into a vein over 5 to 30 minutes. Surgeons also use it as a dye to make structures such as the ureters, parathyroid glands and sentinel lymph nodes easier to see, and hospital teams use it off-label in some cases of severe low blood pressure (vasoplegic shock) and for a nervous-system side effect of the chemotherapy drug ifosfamide. None of this is self-care. It is done by clinicians, at doses and by routes that have nothing in common with a supplement.

In laboratories and microbiology

Methylene blue is one of the oldest biological stains. It is used to stain nerve fibers in living tissue, to color cells for microscopy, and as a redox indicator in analytical chemistry, because it turns colorless when reduced and blue again when oxidized. Laboratory methylene blue is sold as a reagent and is not made or labeled for eating.

It is also sold for aquariums, where fish keepers use it against fungal growth. Those products are not for people either. Kordon’s aquarium solution, for example, is a 2.303% solution with the printed note that it is “not intended for human consumption”.

As a supplement

The newest use is the one this site covers: low-dose oral methylene blue, usually 5 to 25 mg a day, taken as capsules, gummies or drops for cellular energy and focus. That use rests mostly on mechanism and animal research plus a few small human imaging studies, as the research section below explains. Our review of methylene blue benefits and the research behind them goes through each claim, and what makes methylene blue unusual as a molecule explains why it keeps drawing attention.

How methylene blue is made, and why grade matters

Methylene blue is made by organic synthesis. In the classic route, 4-aminodimethylaniline is oxidized in the presence of sodium thiosulfate, the product is reacted with dimethylaniline, oxidized again and then closed into the three-ring thiazine structure. A greener electrochemical route using dimethyl-4-phenylenediamine and sulfide ions has also been proposed. Our guide to what methylene blue is made from walks through the chemistry step by step.

The same reaction produces every grade of methylene blue. What differs is how far the product is purified afterwards and what it is tested for:

• USP grade is made to the United States Pharmacopeia monograph, which sets standards for identity, strength and purity. This is the grade used in medicine and in reputable supplements.
• Laboratory or reagent grade is sold for staining and chemistry. It is not tested or labeled for eating.
• Industrial and aquarium grades are sold for dyeing and fish keeping. They are not for people.

The practical point is that the name on the bottle tells you very little. A lot-numbered certificate of analysis from a named laboratory tells you much more. Our guides to lab grade vs pharmaceutical grade methylene blue, what 99% and USP purity mean and how to tell if methylene blue is real cover what to look for.

How methylene blue works in the body

Methylene blue does several things at once, and each one explains a different use.

It shuttles electrons in mitochondria. Enzymes in the cell that use NADH or NADPH reduce methylene blue to colorless leucomethylene blue. Cytochrome c, a protein in the mitochondrial electron transport chain, then takes the electrons back and turns it blue again. Atamna and colleagues proposed that this cycling may partly explain why methylene blue raised the activity of mitochondrial complex IV by 30% and cellular oxygen use by 37 to 70% in their 2008 cell experiments. Reviews by Rojas and colleagues (2012), Gonzalez-Lima and colleagues (2014) and Tucker and colleagues (2018) set out this “alternative electron carrier” idea in detail. Much of that work is in cells and animals.

It restores hemoglobin. In red blood cells, an NADPH-dependent enzyme reduces methylene blue to leucomethylene blue, which in turn converts methemoglobin back into hemoglobin that can carry oxygen. This is the basis of its main hospital use.

It narrows blood vessels. Methylene blue inhibits nitric oxide synthase and guanylate cyclase, two enzymes involved in relaxing blood vessels, which is why intensive-care teams sometimes use it when blood pressure will not respond to other drugs.

It inhibits monoamine oxidase A. Ramsay and colleagues showed in 2007 that methylene blue is a potent, reversible inhibitor of MAO-A, the enzyme that breaks down serotonin. This is the source of its most important safety risk, covered below.

Its effects follow a hormetic curve. In a 2008 review, Bruchey and Gonzalez-Lima described how methylene blue’s effects rise with dose, then fall, and at high enough doses drop below baseline. Low doses and high doses can do opposite things, which is why the research concentrates on low doses.

How long methylene blue stays in your system

Methylene blue is absorbed well by mouth. In a 2009 study in 16 healthy volunteers, Walter-Sack and colleagues compared 50 mg given into a vein with 500 mg taken as an oral solution and measured an absolute oral bioavailability of 72.3%.

It leaves the blood over hours rather than minutes. Peter and colleagues gave 100 mg to seven volunteers in 2000 and estimated a terminal half-life of 5.25 hours after an intravenous dose. They recovered 28% of the intravenous dose and 18% of the oral dose in urine as methylene blue and its colorless form, which is why urine turns blue or blue-green. That color is expected and harmless.

As a rough guide, a drug is mostly cleared after about five half-lives, which for methylene blue works out to about a day. That half-life comes from one small intravenous study, so read it as an estimate. Our guide to how long methylene blue takes to work covers the other end of the timeline, and our comparison of absorption from liquid and capsules covers the formats.

What the research shows, and what it does not

The evidence falls into three tiers, and most confusion about methylene blue comes from mixing them up.

Human pharmacology is well described. How methylene blue is absorbed, how long it stays in the blood and how it is excreted have been measured in people, as in the studies above. That tells you what the body does with the compound, not what the compound does for thinking or energy.

Human brain studies are few and small, and they point in different directions. In a 2016 randomized, double-blind, placebo-controlled trial in Radiology, Rodriguez and colleagues gave 26 healthy adults either placebo or a single oral dose of 280 mg (about 4 mg per kilogram) of USP grade methylene blue. One hour later, functional MRI showed more activity during attention and short-term memory tasks, and the methylene blue group gave 7% more correct answers during memory retrieval. A follow-up paper from the same team in 2017 reported changes in resting-state brain connectivity. In 2023, though, Singh and colleagues at King’s College London gave healthy volunteers methylene blue into a vein at 0.5 and 1 mg per kilogram and found that global brain blood flow and brain oxygen use went down, not up, the opposite of what they expected. They suggested the hormetic curve as one explanation.

Cell and animal studies make up most of the literature. The Atamna cell work, and a large body of animal research reviewed by Rojas, Gonzalez-Lima and Tucker, supports the mitochondrial mechanism. These studies generate hypotheses. They are not results in people.

What has not been shown matters just as much. The Rodriguez trial used a single dose far larger than a supplement serving and measured effects within an hour. We know of no trial that has tested daily 5 to 25 mg supplement use in healthy adults over months. So the honest description of a methylene blue supplement is a compound that may support cellular energy, with a plausible mechanism and limited human data, not something proven to change how you think. Our articles on methylene blue for brain and cellular health, methylene blue and aging and methylene blue for mental clarity go through the individual claims.

Why methylene blue is controversial

Methylene blue became a wellness trend in the mid-2020s, and the attention ran ahead of the evidence. Harvard Health’s 2025 overview lists what supporters claim (slower aging, better memory, better mood and focus) and points to the 2023 study that found lower brain blood flow instead.

Three concerns come up again and again:

• A serious drug interaction. Combined with common antidepressants, methylene blue can cause serotonin syndrome, which can be fatal.
• The wrong product. Laboratory, industrial and aquarium methylene blue are easy to buy and are not made for people. Harvard Health warns that stain- or dye-grade methylene blue should not be used in humans or animals.
• Overselling. Cell and animal findings get repeated as if they were results in people. We try to avoid that on this site, and we flag it when we see it.

That is also why doctors rarely suggest it for everyday use. Our article on why doctors don’t prescribe methylene blue and our guide to whether you need a prescription for methylene blue explain the clinical view.

Is methylene blue safe to take daily?

For healthy adults who take no interacting medicines, low supplement doses are generally well tolerated, but no long-term trial has tested daily use, so nobody can promise long-term safety. The groups who should not take it at all are well documented:

• People taking serotonergic medicines. StatPearls lists serotonin syndrome as a reported reaction when methylene blue is used with SSRIs, SNRIs, MAOIs, certain opioids and dextromethorphan. A systematic review by Ng and Cameron (2010) found 26 patients who became acutely confused after intravenous methylene blue, and 24 of them were taking a serotonin reuptake inhibitor. Do not combine methylene blue with these medicines, and do not stop a prescribed medicine to make room for it. Talk to your doctor.
• People with G6PD deficiency. StatPearls lists G6PD deficiency as a contraindication because of the risk of hemolysis. If you do not know your status, ask your doctor about a test first.
• Pregnancy and breastfeeding. StatPearls notes that methylene blue may cause fetal harm when given during pregnancy. Do not take it while pregnant, and do not take it while breastfeeding without your doctor’s advice.
• Allergy. Anyone who has had a severe reaction to methylene blue or related thiazine dyes should not take it.

Dose matters too. StatPearls notes that doses above 7 mg per kilogram carry a markedly higher risk of side effects, far above any supplement routine. Healthspan, a clinician-led telehealth service, says its methylene blue dosing typically starts around 5 mg and rises to a maximum of about 25 mg a day. Start at the lowest dose you can take, take it in the morning or early afternoon, and hold it for a week or two before you change anything.

Our guides to who should not take methylene blue, what not to take with methylene blue, methylene blue side effects and why methylene blue can make you feel weird go into more detail.

Methylene blue as a supplement: forms and doses

Supplement methylene blue comes in three main forms. The molecule is the same in each. The format changes how finely you can dose it and whether the dye touches your mouth.

• Capsules give a fixed dose in a shell you swallow. Our 5 mg methylene blue capsules hold 5 mg of USP grade methylene blue and 10 mg of vitamin C each, 60 for $37.99, one a day with food, which suits people who want to start low.
• Gummies are chewed. Our methylene blue gummies hold 10 mg of methylene blue and 25 mg of vitamin C each, 60 for $49.99. They don’t leave the blue mouth that drops can.
• Drops are the most adjustable. Our 1% methylene blue drops give 0.5 mg per drop, so 10 drops make 5 mg. A 50 mL bottle costs $29.99. Drops can stain the mouth unless diluted, and our guide to taking methylene blue drops covers dilution.

NooBlue publishes a report from Contract Testing Laboratories of America on its methylene blue ingredient, covering identity by HPLC and four heavy metals. It is an ingredient-level report, not a test of every finished batch, and it does not state a purity percentage. For daily amounts, see our guide to how many mg of methylene blue to take per day. To compare brands, see our best methylene blue supplements, methylene blue capsules and methylene blue gummies roundups, and our capsules vs liquid comparison. If you would rather buy in person, see whether health food stores and pharmacies stock methylene blue, or browse the NooBlue shop.

If you are comparing methylene blue with other mitochondrial supplements, our methylene blue vs NAD comparison and mitochondrial support supplements guide set out how they differ.

Frequently asked questions about methylene blue

What does methylene blue do to the body?

At low concentrations it cycles between a blue and a colorless form, passing electrons along in mitochondria. It also converts methemoglobin back into working hemoglobin, narrows blood vessels by blocking nitric oxide signaling, and inhibits the enzyme MAO-A, which is why it must not be combined with serotonergic medicines. It turns urine blue or blue-green, which is harmless.

What is methylene blue used for?

In hospitals it is an injectable prescription medicine, mainly for acquired methemoglobinemia, and a surgical dye. In laboratories it is a stain and redox indicator. In fish keeping it is a remedy for fungal growth. As a supplement it is taken by mouth at low doses, usually 5 to 25 mg a day, for cellular energy and focus.

Why are people taking methylene blue now?

Interest grew from research on how it behaves in mitochondria and from a small number of human brain-imaging studies, then spread through wellness media in the mid-2020s. The human evidence for daily supplement use is still limited, and one 2023 study found that it lowered brain blood flow in healthy volunteers.

Is the methylene blue in supplements the same compound used in hospitals?

Yes, the molecule is the same. The route and dose differ: hospital methylene blue is injected at about 1 mg per kilogram of body weight, while supplements provide a few milligrams by mouth. Both should be USP grade, and a supplement should come with a certificate from a named laboratory.

Is methylene blue natural or synthetic?

Synthetic. It does not occur in plants, animals or minerals. Heinrich Caro first made it in 1876, and all methylene blue is still made by chemical synthesis. “Natural” is not a quality marker for it. Purity and testing are.

Where does methylene blue come from?

It comes from organic synthesis. In the classic route, 4-aminodimethylaniline is oxidized with sodium thiosulfate, reacted with dimethylaniline and then oxidized and closed into the thiazine ring. The grade depends on how far the product is purified and tested afterwards.

Is methylene blue the same as the aquarium or lab dye?

Chemically it is the same molecule, but aquarium, industrial and laboratory products are not made or tested for people and are labeled accordingly. Only take methylene blue sold as a supplement with a stated dose and lab paperwork.

Is methylene blue safe to take daily?

For healthy adults on no interacting medicines, low doses are generally well tolerated, but no long-term trial has tested daily supplement use. Do not take it if you take SSRIs, SNRIs, MAOIs, certain opioids or dextromethorphan, if you have G6PD deficiency, or if you are pregnant or breastfeeding. Talk to your doctor if you take any prescription medicine.

How long does methylene blue stay in your system?

One study estimated a terminal half-life of 5.25 hours after an intravenous dose, so most of a dose clears in about a day. Oral methylene blue is well absorbed, with an absolute bioavailability of 72.3% in one trial.

Why does methylene blue work at low doses but not high doses?

Its effects follow a hormetic curve: they rise with dose, then fall, and at high enough doses go below baseline. One explanation is that methylene blue helps only while it can be recycled between its two forms. Beyond that point it can add to oxidative stress instead.

Why don’t doctors prescribe methylene blue for everyday use?

Its established medical uses are narrow and handled in hospital. The everyday use people ask about rests mainly on cell and animal research, and the interaction with serotonergic medicines is a real hazard, so most doctors are cautious.

Can I take methylene blue with antidepressants?

No. Methylene blue inhibits MAO-A, and combining it with SSRIs, SNRIs or MAOIs has been linked to serotonin syndrome, a serious and sometimes fatal reaction. Do not stop an antidepressant on your own to take methylene blue. Talk to your prescriber.

What forms is methylene blue sold in?

Capsules, gummies and drops are the main supplement forms, with some tablets and troches as well. Capsules give a fixed dose you swallow, gummies are chewed, and a 1% solution gives about 0.5 mg per drop for fine control.

The short version

Methylene blue is a synthetic dye from 1876 that became the first synthetic drug, a century-old hospital medicine and lab stain, and now a low-dose supplement. Its biology comes from its ability to cycle between a blue and a colorless form, and its effects follow a curve where more is not better. The human evidence for supplement use is small. The safety rules are clear: no serotonergic medicines, no G6PD deficiency, no pregnancy or breastfeeding, and only USP grade methylene blue with lab paperwork.

Related reading

• What methylene blue is made from
• Methylene blue benefits: what the research shows
• How many mg of methylene blue per day
• Who should not take methylene blue
• Best methylene blue supplements compared

Sources

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