Non-peptide

Methylene blue

Methylene blue is FDA-approved as a drip into a vein for a rare blood disorder. No approval covers memory or mood, where the evidence grade is limited-human: a few small trials. It can cause a deadly reaction with some antidepressants.

fda-approvedchecked Evidence grade limited-human · our assessmentVerified

This page has not been individually reviewed by a clinician.

Fact sheet · 6 facts

every row cites its source and its date
FactValueTierCheckedSource
Also calledmethylthionium chloridepeer-reviewedpubmed.ncbi.nlm.nih.gov
Classnon-peptideprimarydailymed.nlm.nih.gov
Regulatory statusfda-approvedprimaryaccessdata.fda.gov
Status source read2026-10-26primaryaccessdata.fda.gov
Evidence gradelimited-humanour assessmentpeptideindex.ai
Label dosingFrom the ProvayBlue label. It is given by drip into a vein over 5 to 30 minutes, at 1 mg per kilogram of body weight. If the blood level stays above 30% or symptoms persist, one more dose of up to 1 mg per kilogram may be given an hour later. People with moderate or severe kidney disease get a single dose. The prescriber sets the dose.primarydailymed.nlm.nih.gov

Short answer

Methylene blue is FDA-approved as a drip into a vein for a rare blood disorder. No approval covers memory or mood, where the evidence grade is limited-human: a few small trials. It can cause a deadly reaction with some antidepressants.

Our assessment, drawn from the sources below.

What it is

Methylene blue is a blue dye that is also a medicine. It has been used in medicine for centuries [14]. It is not a peptide.

The approved drug is ProvayBlue, a liquid given by drip into a vein [1] [2]. It treats acquired methemoglobinemia, a rare blood disorder [2] [17]. The dye also strongly blocks MAO A, an enzyme that acts on serotonin [10].

Online, drops of it are promoted for brain health and long life [17]. Its color can stain the tongue and urine blue [17].

What the evidence shows

Evidence grade: limited-human · our assessment

The evidence grade is limited-human: for memory and mood, there are only a few small trials in people [8] [9]. In a 2016 trial, 26 healthy adults took one low dose by mouth or a dummy pill [8]. An hour later, brain scans showed more activity during memory tasks [8]. Correct answers on one memory test rose by 7% [8].

In a 2017 trial, 37 people with bipolar disorder took it beside their usual drug [9]. It eased leftover depression and anxiety. It did not help thinking skills [9].

For its approved use, the label reports 31 adults with acquired methemoglobinemia [2]. In 26 of 28 people with a level measured before treatment, the level fell by half or more [2]. In septic shock, a 2024 review of six trials with 302 patients found it may lower early deaths [11]. The review rated that evidence as low certainty [11].

Much of the brain story comes from animals. In mice with a brain injury, it partly kept memory from getting worse [12]. That does not show it helps healthy people.

Known risks

  • The label carries a boxed warning. Methylene blue can cause serotonin syndrome, which can kill, when used with some antidepressants or with opioids [2].
  • Methylene blue strongly blocks MAO A, an enzyme. An enzyme study says this may be why it can cause serotonin toxicity in people who take some antidepressants [10].
  • People with G6PD deficiency, an inherited red blood cell problem, can have their red blood cells break down. The label says they must not get it [2] [13] [17].
  • Some people have had serious allergic reactions [2].
  • It may harm an unborn baby, the label says [2].
  • It can cause confusion, dizziness and trouble seeing. The label advises against driving until these pass [2].
  • In the label's study, the most common problems were headache, diarrhea, nausea and muscle jerks. Low potassium, low magnesium and seizure-like events were on the list too [2].
  • It can make a finger oxygen monitor read too low. It also turns urine blue [2] [17].

What nobody knows yet

  • Nobody knows if methylene blue by mouth helps memory over time. The 2016 brain scan trial tested one dose in 26 healthy adults [8].
  • The bipolar trial found less depression and anxiety in 37 people who also took another drug [9]. Nobody knows if it helps others with depression.
  • In septic shock, the 2024 review rated its evidence as low certainty and called for better trials [11].
  • Experts quoted by NPR in 2025 called the human findings for brain health early [17].
  • Buyers online may not know what is in the bottle. An expert quoted by NPR said oversight of supplements is weak [17].
  • A mouse study after brain injury does not show that it helps healthy people think better [12].

Legitimate ways to get it

The legal way to get methylene blue is ProvayBlue, a prescription drug given by drip into a vein [1] [2]. It is approved for acquired methemoglobinemia in children and adults [2].

Pharmacies may compound with a raw substance that meets a USP standard or is part of an FDA-approved drug [3]. A compounded product is not FDA-approved [5].

Two US trials of methylene blue for memory have finished [15] [16]. The trials block on this page lists open trials with their dates.

  • Approved product

    Approved by FDA as a prescription drug given by drip into a vein.

    Brand names: ProvayBlue

    Manufacturer: Provepharm SAS

    Indication: Acquired methemoglobinemia in children and adults.

    dailymed.nlm.nih.gov

  • Lawful compounding

    Pharmacies may compound with a raw substance that meets a USP standard or is part of an FDA-approved drug. A compounded product is not FDA-approved.

    fda.gov

Recruiting trials

A listing is not a recommendation. Trials have strict eligibility rules. Talk to your doctor and read the official record.

No open trials in the snapshot of .clinicaltrials.gov

How people are getting it anyway

This section describes what happens and is not a recommendation.

Drops of methylene blue are promoted online for brain health and long life [17]. Many of these products are not labeled as dietary supplements [17].

In June 2020, FDA and the Federal Trade Commission sent warning letters to two wellness centers [6] [7]. Each sold methylene blue products online with claims about COVID-19. FDA called the products unapproved new drugs and misbranded drugs [6] [7]. FDA told consumers not to buy or use such products [6].

  • Clinic or med spa

    Wellness centers that sold methylene blue capsules and other methylene blue products on their websites with claims about COVID-19.

    The lawFDA called these products unapproved new drugs and misbranded drugs. Shipping them across state lines is prohibited under federal law.fda.gov

    Documented riskThe products were sold to prevent or treat COVID-19. FDA and the Federal Trade Commission said no study was known to show that they could.fda.gov

    Documented riskFDA advised consumers not to buy or use products it had not approved that were sold with COVID-19 claims.fda.gov

    Enforcement FDA and Federal Trade Commission warning letter to a wellness center that sold methylene blue products online with COVID-19 claims.fda.gov

    Enforcement FDA and Federal Trade Commission warning letter to a wellness center that sold methylene blue capsules online with COVID-19 claims.fda.gov

Sources

  1. [1]Drugs@FDA: ProvayBlue (methylene blue) injection, application 204630Regulatory · primary
  2. [2]DailyMed: ProvayBlue (methylene blue) injection label, revised February 2024Label · primary
  3. [3]FDA: bulk drug substances used in compounding under section 503ARegulatory · primary
  4. [4]FDA: 503A bulk drug substances category list, updated May 2026Regulatory · primary
  5. [5]FDA guidance: compounded drugs that are essentially copies, January 2018Regulatory · primary
  6. [6]FDA warning letter: methylene blue capsules sold with COVID-19 claims, 30 June 2020Regulatory · primary
  7. [7]FDA warning letter: methylene blue products sold with COVID-19 claims, 19 June 2020Regulatory · primary
  8. [8]Randomized trial: methylene blue and brain scans of memory in healthy adults, 2016Rct · peer-reviewed
  9. [9]Randomized crossover trial: methylene blue in bipolar disorder, 2017Rct · peer-reviewed
  10. [10]Enzyme study: methylene blue, MAO A and serotonin toxicity, 2007In vitro · peer-reviewed
  11. [11]Systematic review and meta-analysis: methylene blue in septic shock, 2024Systematic review · peer-reviewed
  12. [12]Mouse study: methylene blue and spatial memory after brain injury, 2025Animal · peer-reviewed
  13. [13]Hematology report: methylene blue and G6PD deficiency, 2024Reference · peer-reviewed
  14. [14]Review: methylene blue as an antidote for methemoglobinemia, 2021Reference · peer-reviewed
  15. [15]ClinicalTrials.gov NCT02380573: methylene blue in healthy aging, mild cognitive impairment and Alzheimer's diseaseReference · primary
  16. [16]ClinicalTrials.gov NCT01836094: USP methylene blue, memory and brain scansReference · primary
  17. [17]NPR: methylene blue wellness claims and the research, December 2025Reference · established-news

Last verified · 6 facts · 9 sources

Primary source: https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=204630

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Information, not medical advice.

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