Methylene Blue for Brain Fog: One Small Scan Study, a Failed Dementia Trial and a Serious Drug Interaction
Wellness influencers sell methylene blue as a mitochondrial booster for focus and energy. In healthy people, the human evidence is one small single-dose brain-scan study. The largest trial of a related drug failed, and the prescription label carries a boxed warning for serotonin syndrome with common antidepressants.
By Kymata Health Editorial Published Last checked
What this article covers
1 evidence profileKey takeaways
From 8 sources- The study behind most brain-boost claims gave 13 healthy adults a single oral dose and 13 a placebo; correct answers on a memory task rose 7% an hour later, alongside changes on brain scans1.
- A 15-month phase 3 trial of LMTM, a methylene blue derivative, in 891 people with mild to moderate Alzheimer’s disease found no benefit at either dose; the drug’s developer, TauRx Therapeutics, funded it4.
- The FDA label for methylene blue injection carries a boxed warning: it may cause serious or fatal serotonin syndrome with SSRIs, SNRIs, MAOIs and opioids6.
- A review of case reports found 26 people became acutely confused after a methylene blue infusion, and 24 of them were taking a serotonin reuptake inhibitor7.
- People with G6PD deficiency should not take it: the label lists G6PD deficiency as a contraindication because of the risk of severe hemolytic anemia6.
The evidence, graded
Pulled from the trial tables in our evidence profiles. Grades follow our evidence-grading policy.
Graded findings
1 row- DGrade DBrain activity and memory retrieval after one doseImproved fMRI responses during sustained-attention and short-term memory tasks rose, and correct responses during memory retrieval increased by 7%, compared with placebo.Methylene blue · RCT · n=26 · 2016 · PMID 27351678
What methylene blue is, and why it is trending
Methylene blue is a blue dye and a prescription drug. In the US, the approved injection is indicated for acquired methemoglobinemia, a blood disorder in which hemoglobin cannot carry oxygen normally, at 1 mg/kg given into a vein6. The label describes it as an oxidation-reduction agent6, the property marketers point to when they call it a mitochondrial or energy booster.
The same label says methylene blue appears to be a potent reversible inhibitor of monoamine oxidase, the enzyme that MAOI antidepressants block6. That second property drives most of the safety concerns below.
Online, methylene blue is sold as drops and tablets for focus, energy and longevity. We found no randomized trial of these consumer products in healthy people, and their label doses are not the doses used in the studies below.
The evidence in healthy people: one small study
The trial cited most often is a 2016 randomized, double-blind, placebo-controlled study of 26 adults aged 22 to 621. Thirteen took a single oral dose of methylene blue and 13 took a blue food-dye placebo, with MRI brain scans during attention and short-term memory tasks before and 1 hour later1. The methylene blue dose was 280 mg, about 4 mg/kg, which the authors described as low1.
Methylene blue increased activity in brain regions used for attention and memory, and correct responses during memory retrieval rose by 7%1. That is a short-term lab result after one dose. It does not show better focus in daily life, an effect of repeated use, or safety over months1.
Other small trials: mixed signals
A handful of trials have tested methylene blue as an add-on in psychiatry, each with only a few dozen people:
- Claustrophobia, 2014: 42 adults took 260 mg of methylene blue or placebo right after a short exposure-therapy session2. People whose fear had dropped during the session did better a month later on methylene blue, but people who were still very afraid tended to do worse2.
- PTSD, 2017: 42 patients had 5 daily imaginal exposure sessions followed by 260 mg of methylene blue or placebo, or went on a waitlist3. Both exposure groups improved, and methylene blue gave better evaluator-rated response and quality of life than placebo3.
- Bipolar disorder, 2017: in a 6-month crossover trial in 37 people already taking lamotrigine, a 195 mg dose improved depression and anxiety scores compared with a 15 mg comparison dose, with no significant effect on cognition8.
Alzheimer’s disease: the large trial came back negative
Methylene blue chemistry has been tested as an Alzheimer’s drug because it can stop tau protein from clumping in lab and mouse studies4. In a phase 3 trial at 115 sites in 16 countries, 891 people with mild to moderate Alzheimer’s disease took 75 mg or 125 mg of LMTM twice a day, or a 4 mg control dose, for 15 months4.
Neither dose slowed decline on the co-primary memory and daily-function scales, and the authors concluded the results do not suggest benefit as an add-on treatment4. TauRx Therapeutics, which develops LMTM, funded the trial, and four authors were officers of the company with financial interests in it4.
A second phase 3 trial in 800 people with mild disease was later reanalyzed by largely the same author team, comparing small non-randomized subgroups taking LMTM without other Alzheimer’s drugs5. Those revised analyses were positive, but the authors themselves said a further randomized trial is required5. TauRx also sponsored the 800-person trial5.
Safety: who should avoid methylene blue
Most safety data come from the prescription injection, which is given under medical supervision6. The small trials above were short, so they say little about months of daily use. Groups at particular risk:
- Anyone on an antidepressant or other serotonergic drug: the label says to avoid SSRIs, SNRIs, MAOIs and opioids, and also lists bupropion, buspirone, clomipramine, mirtazapine, linezolid and dextromethorphan as interacting drugs6. Serotonin syndrome can cause agitation, fever, a fast heart rate, tremor and seizures, and some reported cases were fatal6. The label also tells patients not to take serotonergic drugs within 72 hours after the last dose6.
- The case-report evidence: a systematic review found 26 people developed acute confusion after a methylene blue infusion; 24 were taking a serotonin reuptake inhibitor and 1 was taking clomipramine, and serotonin syndrome was a possible diagnosis in all 257.
- G6PD deficiency: the label contraindicates methylene blue because it can cause severe hemolysis and anemia in this inherited condition6.
- Pregnancy and breastfeeding: the label warns of possible fetal harm and advises stopping breastfeeding for up to 8 days after treatment6.
- Kidney or liver problems: drug exposure rose 52% to 192% with mild to severe kidney impairment after one dose, and the label advises longer monitoring with any liver impairment6.
- Side effects and lab tests: the label lists headache, nausea, diarrhea, confusion, dizziness and blue discoloration of skin and body fluids, advises against driving until such effects pass, and notes it can lower pulse-oximeter readings and interfere with urine dipstick tests6.
- Dose and product: the studies above gave single or repeated doses of 195 to 280 mg under research supervision128. Those were research conditions, not guidance for self-use, and consumer products vary. See the methylene blue page for the studied forms.
Quick answers
Common questions
4 answersIs methylene blue FDA approved?
Methylene blue injection is FDA approved for acquired methemoglobinemia6. That approval does not cover drops or tablets sold for focus or energy.
Can I take methylene blue with an SSRI?
The prescribing label says to avoid the combination because it may cause serious or fatal serotonin syndrome6.
Does methylene blue improve memory?
In a 26-person trial in healthy adults, one dose raised correct memory answers by 7% an hour later compared with placebo1. We found no long-term trial in healthy people.
Why does methylene blue turn urine blue?
It is a dye; the label warns that it may cause blue discoloration of the skin and body fluids6.
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References
8 sources. Numbers in the text link here.
Sources cited in this article
8 sources- 1Multimodal Randomized Functional MR Imaging of the Effects of Methylene Blue in the Human BrainRadiology, 2016 · PMID 27351678
- 2Effects of post-session administration of methylene blue on fear extinction and contextual memory in adults with claustrophobiaAm J Psychiatry, 2014 · PMID 25018057
- 3Enhancing Extinction Learning in Posttraumatic Stress Disorder With Brief Daily Imaginal Exposure and Methylene Blue: A Randomized Controlled TrialJ Clin Psychiatry, 2017 · PMID 28686823
- 4Efficacy 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 trialLancet, 2016 · PMID 27863809
- 5Potential of Low Dose Leuco-Methylthioninium Bis(Hydromethanesulphonate) (LMTM) Monotherapy for Treatment of Mild Alzheimer’s Disease: Cohort Analysis as Modified Primary Outcome in a Phase III Clinical TrialJ Alzheimers Dis, 2018 · PMID 29154277
- 6PROVAYBLUE (methylene blue) injection: prescribing informationU.S. Food and Drug Administration, 2024
- 7The role of methylene blue in serotonin syndrome: a systematic reviewPsychosomatics, 2010 · PMID 20484716
- 8Methylene blue treatment for residual symptoms of bipolar disorder: randomised crossover studyBr J Psychiatry, 2017 · PMID 27284082
Methylene blue is FDA-approved only as a prescription injection; products sold as supplements or dyes are not FDA-approved drugs. This article summarizes published research; it is not a guide to using any product. Talk to your clinician or pharmacist, especially if you take prescription medicines. This page has no product or affiliate links.