Methylene blue
Summary
Methylene blue is an FDA-approved injectable drug for methemoglobinemia that is also sold as a nootropic. One 26-person brain-imaging study found a single low dose raised memory-task activity (grade D). It can cause serious or fatal serotonin syndrome with common antidepressants, so we do not link to products.
Key facts
- A blue dye and prescription drug (ProvayBlue) given by injection for methemoglobinemia[4]
- May cause serious or fatal serotonin syndrome with SSRIs, SNRIs, MAOIs and opioids[4]
- The drug label lists G6PD deficiency as a contraindication because of hemolytic anemia[4]
- A single low oral dose increased fMRI activity during attention and memory tasks and correct memory responses by 7% in 26 adults[1]
- FDA says it is not known whether oral use carries the same serotonin syndrome risk as intravenous doses[3]
- 1 graded human outcome on this page
- October 11, 2026
How it works
ProposedMethylene blue inhibits monoamine oxidase A, which breaks down serotonin; this is the proposed cause of its interaction with serotonergic drugs. Its proposed cognitive effect involves mitochondrial electron transfer, which has not been established in people.[3]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Brain activity and memory retrieval after one dose | Improved | Grade D | RCT · n = 26 · 2016 Healthy adults aged 22–62 Form: Oral methylene blue · Dose: Single low dose (amount not stated in the abstract) · Duration: 1 hour fMRI responses during attention and short-term memory tasks rose, and correct memory responses increased by 7%, compared with placebo. | 27351678 (opens PubMed)Source [1] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Methylene blue (oral solution or tablets) | Varies[4] | Oral bioavailability is not given in our sources; the approved product is an injection.[4] | Prescription labeling lists headache, diarrhea, nausea and seizure-like events among common reactions to the injection.[4] | Attention and memory imaging (single dose) |
Studied doses
Doses studied in human trials ranged from a single low oral dose in a brain-imaging study; no longer-term supplement trial was found.[1]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Who should be careful
- People on antidepressants or opioids
- Serotonin syndrome, which can be fatal, has been reported with these drugs.[4][2]
- People with G6PD deficiency
- It can cause hemolytic anemia and is contraindicated.[4]
- Pregnancy and breastfeeding
- The label advises use in pregnancy only if benefit justifies fetal risk and pausing breastfeeding for up to 8 days after a dose.[4]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Frequently asked questions
Why is there no buying link for methylene blue?
Its main risk, serotonin syndrome with common antidepressants and opioids, can be fatal, and the only cognitive data is one single-dose imaging study. We judged that the risk outweighs the evidence.[4][1]
Does methylene blue improve memory?
One 26-person study found a single low dose raised brain activity on fMRI and memory-task accuracy by 7% an hour later. No longer trial was found.[1]
Is oral methylene blue safer than the injection?
FDA has said it is not known whether oral or low doses carry the same serotonin syndrome risk.[3]
Who must not take methylene blue?
People with G6PD deficiency and anyone on SSRIs, SNRIs, MAOIs or opioids, per the drug label.[4]
Sources
- [1]Multimodal Randomized Functional MR Imaging of the Effects of Methylene Blue in the Human Brain.. Radiology, 2016. RCT
- [2]The role of methylene blue in serotonin syndrome: a systematic review.. Psychosomatics, 2010. systematic-review
- [3]FDA Drug Safety Communication: Updated information about the drug interaction between methylene blue (methylthioninium chloride) and serotonergic psychiatric medications. U.S. Food and Drug Administration, 2011. safety-communication
- [4]PROVAYBLUE (methylene blue) injection prescribing information. U.S. Food and Drug Administration, 2024. label
What changed
- First draft. Every PMID checked against NCBI E-utilities (title, year and journal taken from the PubMed record) and abstracts read for each cited row. Product details in Where to buy read from the brand page on the date shown. Self-reviewed in a second strict pass (no independent reviewer yet).