Key statistics
- 1 to 4 mg/kg: the “low” dose band in the rat memory studies reviewed by Rojas and colleagues in 2012. Doses of 50 mg/kg or more caused adverse effects.
- 280 mg once: the oral dose (about 4 mg/kg) in the only randomized human brain-imaging trial, which enrolled 26 healthy adults and found 7% more correct memory-retrieval responses one hour later.
- 72.3%: the average absolute oral bioavailability of methylene blue in 16 healthy volunteers.
- About 24 hours: the half-life in humans stated on the prescription injection’s label.
- 0.07 µM: the concentration that half-inhibits the enzyme MAO-A in the lab, which is why methylene blue must not be combined with serotonergic medicines.
- 13 of 14: reported cases of methylene blue nervous-system toxicity that met formal criteria for serotonin toxicity.
- 891 patients: the largest trial we found of a methylene blue compound (the derivative LMTM), which showed no benefit on its main outcomes.
Methylene blue is discussed everywhere in nootropic and longevity circles, usually without numbers. This page collects the figures that appear in the published research: the doses studied in animals and people, how much reaches the blood, how long it stays, how strongly it blocks MAO-A, what the human trials measured, and where the evidence stops. Every figure links to the paper or label it comes from, and each is described with its species, route and study type so you can judge how far it applies to you.
NooBlue sells methylene blue capsules, gummies and drops, so we have a commercial interest in this subject. We have tried to report the research as it stands, including the trials that found nothing. For practical dosing, see our methylene blue dosage guide. For safety, see our methylene blue side effects guide.
Methylene Blue Research Statistics at a Glance
| Statistic | Figure | Study type | Source |
|---|---|---|---|
| Low dose band in rat memory studies | 1 to 4 mg/kg (4 mg/kg most reliable after one dose) | Review of animal studies | Rojas et al., 2012 |
| Dose with adverse effects in rats | 50 mg/kg or more | Review of animal studies | Rojas et al., 2012 |
| Human brain imaging trial dose | 280 mg once (about 4 mg/kg), 26 adults | Randomized controlled trial | Rodriguez et al., 2016 |
| Change in correct memory responses | 7% increase, one hour after dosing | Randomized controlled trial | Rodriguez et al., 2016 |
| Oral absolute bioavailability | 72.3% (plasma), 16 healthy adults | Crossover pharmacokinetic study | Walter-Sack et al., 2009 |
| Half-life in humans | About 24 hours | Prescription label | ProvayBlue label |
| Standard injectable dose | 1 mg/kg into a vein | Prescription label | ProvayBlue label |
| MAO-A inhibition (IC50) in the lab | 0.07 µM | Enzyme assay | Delport et al., 2017 |
| Peak blood level after 0.75 mg/kg IV | 500 ng/mL (1.6 µM) | Human data cited in a review | Gillman, 2011 |
| Nerve toxicity cases meeting serotonin toxicity criteria | 13 of 14 | Review of case reports | Gillman, 2011 |
| Adverse effects in hospital use | 4.9% of 185 patients | Case series over 24 years | Rothenberg et al., 2025 |
| Largest trial we found of a methylene blue compound | 891 patients, 15 months, no benefit on main outcomes | Phase 3 randomized trial of LMTM | Gauthier et al., 2016 |
What Doses of Methylene Blue Appear in the Research?
The doses in the literature span more than a hundredfold, and the route matters as much as the number. The best-known review of the memory research, by Rojas, Bruchey and Gonzalez-Lima in Progress in Neurobiology (2012), pulls together rat and mouse studies in which methylene blue was mostly injected into the abdomen. In those studies, low doses of 1 to 4 mg/kg and an intermediate dose of 10 mg/kg caused no general behavioral side effects, 4 mg/kg was the most reliable single dose for improving memory, and doses of 50 mg/kg or more reduced activity and food intake and should be avoided (Rojas et al., 2012).
| Context | Dose | Route | Source |
|---|---|---|---|
| Rat memory studies, “low” band | 1 to 4 mg/kg | Mostly injected into the abdomen | Rojas et al., 2012 |
| Rat studies with adverse effects | 50 mg/kg or more | Injected into the abdomen | Rojas et al., 2012 |
| Human brain-imaging trials | 280 mg once (about 4 mg/kg) | Oral | Rodriguez et al., 2016 and 2017 |
| Prescription injection | 1 mg/kg | Intravenous | ProvayBlue label |
| Hospital uses reviewed | 1 to 7.5 mg/kg | Intravenous | Gillman, 2011 |
| Poison center cases | Median 1 mg/kg (interquartile range 1 to 2) | Intravenous | Rothenberg et al., 2025 |
| LMTM phase 3 trial | 75 or 125 mg twice a day (control 4 mg twice a day) | Oral tablets | Gauthier et al., 2016 |
| NooBlue capsule | 5 mg (about 0.07 mg/kg for a 70 kg adult) | Oral | Product label |
Two points stand out. The human trial dose of 280 mg is 56 times one of our 5 mg capsules, so the trial results cannot be carried over to supplement servings. And the doses that produced serotonin toxicity in hospital patients (1 mg/kg into a vein) sit inside the normal injectable range, which is why the interaction section below matters even though supplement servings are far smaller.
How Much Reaches the Blood? Absorption and Half-Life Data
Two human studies measured how methylene blue behaves when swallowed, and they reached different conclusions.
- High bioavailability in plasma. In a crossover study of 16 healthy adults, researchers compared 50 mg given into a vein with 500 mg taken by mouth as an aqueous solution. The average absolute bioavailability of the oral dose was 72.3% (plus or minus 23.9%), measured in plasma (Walter-Sack et al., 2009).
- Much lower exposure in whole blood. An earlier study gave 7 volunteers 100 mg by vein and by mouth. Measured in whole blood, the area under the curve after the oral dose was far lower (9 vs 137 nmol/min/ml), and urinary excretion of methylene blue and its colorless form was 18% of the dose after oral use vs 28% after injection. The estimated terminal half-life after injection was 5.25 hours. Rat work in the same paper found oral dosing gave higher levels in the gut wall and liver and lower levels in the brain than injection (Peter et al., 2000).
- Label half-life. The prescription injection’s label states a half-life of about 24 hours in humans (ProvayBlue label).
The studies measured different things (plasma in one, whole blood in the other) and used different doses, so their numbers are not directly comparable. The fair summary is that a good share of a swallowed dose is absorbed, the liver and gut see more of it than the brain does, and it takes days, not hours, to clear fully. Our page on methylene blue half-life works through what that means for daily use.
What Methylene Blue Does in the Mitochondria
Methylene blue works as an alternative electron carrier. A 2018 review in Molecular Neurobiology describes it rerouting electrons in the mitochondrial electron transfer chain directly from NADH to cytochrome c, increasing the activity of complex IV while reducing oxidative stress (Tucker et al., 2018). The Rojas review makes a related point: its effects “are not determined by regular drug-receptor interactions,” because it acts as a redox agent inside the respiratory chain.
A 2014 paper in Biochemical Pharmacology by the same Texas group proposed brain mitochondrial respiration as a research target and described low-dose USP methylene blue as one of three approaches to raise it, alongside near-infrared light and a diet higher in ketone bodies (Gonzalez-Lima et al., 2014). That is a proposal backed mostly by animal data, not a human outcome. Our explainer on how methylene blue works covers the chemistry in more depth, and our methylene blue vs CoQ10 comparison sets it against a better-known mitochondrial nutrient.
Why the Dose-Response Curve Matters
Methylene blue shows a hormetic dose response: low and high doses have opposite effects (Rojas et al., 2012). At low doses it cycles electrons and supports cell respiration. At high local concentrations it can pull electrons away from the chain and act as a pro-oxidant, and in rats, doses of 50 mg/kg or more caused visible harm. With most supplements an extra dose is wasted. With methylene blue, more can work against you, which is why accurate dosing and a known strength per serving matter more than usual.
This is also why the purity of what you buy matters. The USP monograph requires methylene blue to contain 97.0% to 103.0% of the compound on the dried basis (USP-NF). Our guide to methylene blue purity explains what that standard covers and what it does not.
Human Trials: What Has Actually Been Measured
The human evidence in healthy people is small. In a randomized, double-blind, placebo-controlled trial published in Radiology in 2016, 26 healthy adults aged 22 to 62 were assigned to a single 280 mg oral dose of methylene blue (about 4 mg/kg) or placebo. One hour later, methylene blue increased the brain’s response in the insular cortex during a sustained-attention task and in prefrontal, parietal and occipital areas during a short-term memory task, and it was associated with a 7% increase in correct memory-retrieval responses (Rodriguez et al., 2016). A 2017 follow-up paper from the same team, with the same single 280 mg dose, reported stronger resting-state connectivity between regions tied to perception and memory (Rodriguez et al., 2017).
The largest human trials we found used LMTM (leuco-methylthioninium), a stabilized reduced form of the same molecule, in patients diagnosed with a neurodegenerative memory condition. In a 15-month phase 3 trial of 891 patients across 16 countries, LMTM at 75 or 125 mg twice a day showed no benefit over a 4 mg twice-daily control on either main outcome. The most common side effects at the higher doses were digestive and urinary, and the trial was funded by the drug’s developer, TauRx (Gauthier et al., 2016).
Methylene blue also has a long clinical history. A 2019 review in CNS Drugs notes it has been used in psychiatry for over a century, and it describes it as usually well tolerated but calls for caution because it inhibits MAO-A (Alda, 2019). For how these findings compare with other options, see methylene blue vs other nootropics and methylene blue vs modafinil.
Safety Data: The MAO-A Interaction in Numbers
The best-quantified human risk is the interaction with serotonergic medicines. Kinetic tests on purified human enzyme showed methylene blue is a potent reversible inhibitor of MAO-A, with much weaker action on MAO-B (Ramsay et al., 2007). A 2017 study measured its half-inhibition concentration for MAO-A at 0.07 µM (Delport et al., 2017).
A 2011 review in the Journal of Psychopharmacology found that 13 of 14 reported cases of methylene blue nervous-system toxicity met the Hunter Serotonin Toxicity Criteria. It cited human data in which an intravenous dose of only 0.75 mg/kg produced a peak blood level of 500 ng/mL (1.6 µM), enough to inhibit MAO-A in the brain, and it noted that severe serotonin toxicity has occurred at 1 mg/kg (Gillman, 2011). The prescription injection’s label carries a boxed warning of serious or fatal serotonin syndrome with SSRIs, SNRIs, MAO inhibitors and opioids, lists G6PD deficiency as a contraindication because of the risk of hemolytic anemia, and warns of possible harm in pregnancy.
Outside that interaction, adverse effects in hospital use were uncommon. A 24-year review of 185 patients given methylene blue by a New York poison center found adverse effects attributed to it in 9 cases (4.9%), including one case of hemolysis (Rothenberg et al., 2025). Read our guides to methylene blue and serotonin syndrome, methylene blue interactions and methylene blue and G6PD deficiency before you take it, and see who should not take methylene blue.
Where Methylene Blue Research Is Concentrated
Read this table as a map of what researchers have studied, not as a list of things a supplement does. Most entries describe animal, cell or clinical work at doses and routes unrelated to supplement servings.
| Research area | What has been studied | Evidence type | Representative source |
|---|---|---|---|
| Memory and attention | Memory consolidation in rodents, brain activity in one human imaging trial | Mostly animal, one small human trial | Rojas et al., 2012, and Rodriguez et al., 2016 |
| Brain cell protection | Nerve cell protection in animal models of injury and degeneration | In vitro and animal | Tucker et al., 2018 |
| Aging and skin | Oxidative stress in aging cells and cultured skin models | Cell and tissue models, review | Xue et al., 2021 |
| Psychiatry | Psychiatric uses over more than a century | Clinical review | Alda, 2019 |
| Established hospital use | Injected methylene blue for methemoglobinemia | Clinical case series and label | Rothenberg et al., 2025 |
| Safety and interactions | MAO-A inhibition and serotonin toxicity | Enzyme assays and case reports | Ramsay et al., 2007, and Gillman, 2011 |
One note on the aging research: the 2021 Cells review that ranks first for this search was written by a group whose senior author founded a skincare company, Mblue Labs, as the paper’s conflict of interest statement discloses (Xue et al., 2021). That does not make it wrong, but it is worth knowing. Our reviews of methylene blue for anti-aging and methylene blue for skin go through that literature.
How to Read a Methylene Blue Study Without Being Misled
- Check the route before comparing doses. The alarming figures, such as serotonin toxicity at 1 mg/kg, come from injections into a vein. Swallowed methylene blue passes through the gut and liver first, and the Peter study found lower brain levels after oral dosing in rats. A milligram figure without a route is not a comparable number.
- Separate lab concentrations from doses. The 0.07 µM MAO-A figure describes purified enzyme in a test tube. It matters because human blood levels after clinical doses reach well above it.
- Note the species. The 1 to 4 mg/kg memory band comes from rats and mice. Results in animals are a reason to run human trials, not a substitute for them.
- Check whether the paper is a review or a primary study. Several of the most cited methylene blue papers are reviews that summarize other people’s data. A claim that traces back only to reviews of animal work supports “studies suggest,” not “research shows.”
- Look at funding and conflicts. The largest trial was funded by the developer of LMTM, and the leading anti-aging review discloses a skincare company. Both facts are in the papers themselves.
What the Research Does Not Show
- No trial has tested supplement servings. No published human study has measured cognitive or energy effects at 5 to 10 mg a day.
- No established supplement dose. The animal and human doses above are research doses. The papers do not translate them into a daily serving, and anyone quoting an “optimal” supplement dose is going beyond them.
- Little long-term data in healthy adults. Clinical experience is mostly short-term hospital use. Daily use over years in healthy people has not been studied.
- Human benefit is unproven for most proposed uses. The neuroprotection findings come mainly from cells and animals, and the largest human trial of a methylene blue compound was negative on its main outcomes.
What These Numbers Mean If You Take a Supplement
A 5 mg capsule is about 0.07 mg/kg for a 70 kg adult, a small fraction of every research dose above. That is a deliberate choice given the hormetic curve, but it also means the published results cannot be assumed to apply at that amount. Our 5 mg methylene blue capsules contain 5 mg of USP-grade methylene blue and 10 mg of vitamin C, one a day with food. Our methylene blue gummies contain 10 mg with 25 mg of vitamin C, and our 1% methylene blue drops give 0.5 mg per drop. Our quality page links a CTLA report on the raw methylene blue ingredient (lot 2025022801) with an HPLC identity result and heavy-metal results. It covers the ingredient only, not each finished batch, and it gives no purity percentage.
Whatever you choose, the safety numbers apply at any dose: never combine methylene blue with serotonergic medicines, and do not take it with G6PD deficiency or while pregnant or breastfeeding. Our overview of methylene blue benefits covers what the research suggests in plainer terms, and is methylene blue safe to take daily covers regular use.
Methodology
We searched PubMed for methylene blue studies on dosing, pharmacokinetics, cognition, clinical trials and serotonin toxicity, and read each paper’s abstract, plus the full text where it was freely available, in Sep 2026. Every figure on this page appears in the cited source. Nothing has been averaged across studies or estimated, apart from the per-kilogram conversion for a 70 kg adult, which is simple arithmetic. Reviews are labeled as reviews, and animal results are labeled as animal results. This page summarizes published research and is not medical advice.
Frequently Asked Questions
What dose of methylene blue is used in research?
It depends on the species and route. Rat memory studies used low doses of 1 to 4 mg/kg, mostly injected. The human brain-imaging trials used one 280 mg oral dose, about 4 mg/kg. The prescription injection is 1 mg/kg into a vein. Supplement servings are much smaller: a 5 mg capsule is about 0.07 mg/kg for a 70 kg adult, and no trial has tested that amount.
Is methylene blue backed by clinical trials?
For its hospital use, yes: injected methylene blue is an established prescription drug, and a 24-year case series found improvement in 98% of 185 patients. For focus, energy or aging in healthy people, the human evidence is one small single-dose imaging trial of 26 adults at 280 mg. The largest trial we found of a related compound, LMTM, showed no benefit on its main outcomes.
Why don’t doctors recommend methylene blue?
Many doctors are cautious because the human evidence for supplement uses is thin and the interaction risk is real. A Harvard Health Publishing article makes the point that short-term use of a pharmaceutical-grade product under medical supervision is different from buying a supplement online and taking it daily. Methylene blue also blocks MAO-A, so it can cause serotonin syndrome with common antidepressants. Talk to your doctor before starting.
Is methylene blue toxic to the body?
Toxicity depends on dose and on what else you take. In rats, doses of 50 mg/kg or more caused adverse effects, while 1 to 4 mg/kg did not. In a hospital series of 185 patients given about 1 to 2 mg/kg, adverse effects were attributed to methylene blue in 4.9%. The serious risks are serotonin syndrome with serotonergic medicines and red blood cell breakdown in people with G6PD deficiency.
What warning does the methylene blue drug label carry?
The prescription injection’s label has a boxed warning that it may cause serious or fatal serotonin syndrome when used with serotonergic drugs and opioids, including SSRIs, SNRIs and MAO inhibitors. It also lists G6PD deficiency and severe allergy to thiazine dyes as contraindications, warns of possible harm in pregnancy and advises stopping breastfeeding for up to 8 days after a dose.
Is methylene blue an MAO inhibitor?
Yes. Tests on purified human enzyme show it is a potent reversible inhibitor of MAO-A, with a reported half-inhibition concentration of 0.07 µM, and much weaker action on MAO-B. That is why it must not be combined with serotonergic medicines, and why 13 of 14 reviewed cases of its nervous-system toxicity were serotonin toxicity.
How long does methylene blue stay in the body?
The prescription label gives a half-life of about 24 hours in humans. One small study estimated a terminal half-life of 5.25 hours in whole blood after injection, so figures vary with how it is measured. Either way, it takes several days to clear fully, which is why blue or green urine can persist for a while after a dose.
Next Steps
If you decide to try methylene blue after reading the research, start with the lowest fixed dose, check the safety list above, and give any change a few weeks before you judge it.
More research-based guides: best methylene blue supplements, methylene blue for brain fog, methylene blue liver safety, methylene blue side effects on skin, the NooBlue shop and about NooBlue.
Sources
- Rojas JC, Bruchey AK, Gonzalez-Lima F. Neurometabolic mechanisms for memory enhancement and neuroprotection of methylene blue. Progress in Neurobiology. 2012;96(1):32-45. PubMed 22067440, full text
- Rodriguez P, Zhou W, Barrett DW, et al. Multimodal randomized functional MR imaging of the effects of methylene blue in the human brain. Radiology. 2016;281(2):516-526. PubMed 27351678
- Rodriguez P, Singh AP, Malloy KE, et al. Methylene blue modulates functional connectivity in the human brain. Brain Imaging and Behavior. 2017;11(3):640-648. PubMed 26961091
- Walter-Sack I, Rengelshausen J, Oberwittler H, et al. High absolute bioavailability of methylene blue given as an aqueous oral formulation. European Journal of Clinical Pharmacology. 2009;65(2):179-189. PubMed 18810398
- Peter C, Hongwan D, Küpfer A, Lauterburg BH. Pharmacokinetics and organ distribution of intravenous and oral methylene blue. European Journal of Clinical Pharmacology. 2000;56(3):247-250. PubMed 10952480
- Tucker D, Lu Y, Zhang Q. From mitochondrial function to neuroprotection: an emerging role for methylene blue. Molecular Neurobiology. 2018;55(6):5137-5153. PubMed 28840449
- Gonzalez-Lima F, Barksdale BR, Rojas JC. Mitochondrial respiration as a target for neuroprotection and cognitive enhancement. Biochemical Pharmacology. 2014;88(4):584-593. PubMed 24316434
- Gauthier S, Feldman HH, Schneider LS, et al. Efficacy and safety of tau-aggregation inhibitor therapy in patients with mild or moderate Alzheimer’s disease: a randomised, controlled, double-blind, parallel-arm, phase 3 trial. Lancet. 2016;388(10062):2873-2884. PubMed 27863809
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- Xue H, Thaivalappil A, Cao K. The potentials of methylene blue as an anti-aging drug. Cells. 2021;10(12):3379. PubMed 34943887
- ProvayBlue (methylene blue) injection, prescribing information, revised 2/2024. DailyMed
- Methylene Blue monograph, USP-NF. USP-NF
- Goldman L. What to know about methylene blue. Harvard Health Publishing. health.harvard.edu
- NooBlue product pages and quality page (label amounts and the CTLA ingredient report), read Sep 2026. nooblue.com/quality
