Methylene Blue for Brain Fog: Can It Help With Post-COVID Cognitive Decline?

Last updated: September 27, 2026 · Originally published: March 21, 2026 · By Eternal Elixir Editorial

Quick answer: No clinical trial has tested methylene blue for brain fog after COVID-19. We searched PubMed and the ClinicalTrials.gov register in September 2026 and found no published or registered trial of it for post-COVID memory or concentration problems, so nobody can honestly say it helps there. The research on methylene blue and the brain is small: two single-dose imaging studies in healthy adults, one of which found 7% more correct answers on a memory task an hour after 280mg, and a 2023 study in which it lowered blood flow to the brain. If brain fog has hung around for weeks after an illness, see your GP first. If you are a healthy adult who wants to try methylene blue for focus, our pick is Eternal Elixir Methylene Blue Capsules: one 10mg capsule a day for $1.00. Do not take it with SSRI, SNRI or MAOI antidepressants or other serotonergic medicines, if you have G6PD deficiency, if you are pregnant or breastfeeding, or if you are under 18.

Eternal Elixir makes the methylene blue capsules and drops in this guide, and they are our pick. Below we cover what methylene blue does in the brain, what the human studies found and what they left out, whether anyone has tested it for brain fog after an illness, and what each option sold in Australia costs per dose. Every study we mention is listed in the sources at the end.

Methylene blue and brain fog after COVID-19: no trials yet

It hasn’t been tested. This is everything we could find that comes close to the question:

• A 2021 letter, not a study. Four doctors from a cardiac anaesthesia department in New Delhi wrote to Medical Hypotheses arguing that methylene blue should be studied for thinking and memory problems after COVID-19, but they did not test it on anyone (Magoon 2021). Their case rests on its effects on mitochondria in other settings.
• An eight-person pilot during infection. This was not a brain fog trial: a clinic in the Bahamas treated eight people during an active COVID-19 infection with a methylene blue and light treatment in the nose and mouth, and some also took methylene blue by mouth (Hepburn 2022). There was no comparison group and no memory or attention testing, and the lead author is medical director of a company that filed a patent on the protocol. The authors reported few lingering symptoms in a survey a year later, but with eight people and nothing to compare them against, that cannot show methylene blue made any difference.
• No registered trials. A September 2026 search of ClinicalTrials.gov for methylene blue with long COVID, post-COVID or brain fog as the condition returned no trials of it for those problems.

Healthdirect, the Australian Government’s health information service, says there are currently no recommended medicines for long COVID and suggests regular appointments with your doctor to manage symptoms. Brain fog that lasts for weeks after an illness deserves a proper check, because your GP can look for other causes and review the medicines you already take, and that review matters for methylene blue (see the next section). Don’t use a supplement to put off that appointment.

Who should not take methylene blue

Read this before anything else. Do not take methylene blue, at any dose, if one of these applies to you:

• You take an SSRI, SNRI, MAOI or another serotonergic medicine. Methylene blue is a potent, reversible inhibitor of MAO-A, the enzyme that breaks down serotonin, and it has been reported to trigger serotonin toxicity in people taking SSRIs (Ramsay 2007). Pharmacologist Lorne Hofseth lists agitation, confusion, high fever, a rapid heart rate and muscle stiffness among the signs, with seizures or death in severe cases (Hofseth 2025).
• You have G6PD deficiency, or a family history of it and have never been tested. A hospital pharmacy review lists methylene blue among the medicines that should not be used until a G6PD test has been done (Belfield 2018).
• You are pregnant or breastfeeding.
• You are under 18.

Expect blue or green urine. In the memory study described below, every person given methylene blue reported blue urine afterwards and nobody in the placebo group did (Rodriguez 2016). If you take any prescription medicine, talk to your doctor or pharmacist before you start. Our guide to serotonin syndrome, MAO inhibition and methylene blue covers the interaction in detail.

What methylene blue does in the brain

Methylene blue is a synthetic dye that doctors have used as a hospital medicine for more than a century, and it can cross the barrier that protects the brain (Hofseth 2025). Two of its actions explain why people talk about it for focus and memory.

It passes electrons along in the mitochondria

At low doses, methylene blue can accept electrons and hand them on inside the mitochondrial electron transport chain, which is why researchers call it an electron cycler. A review of the animal and cell research links its memory effects in rodents to the respiratory enzyme cytochrome oxidase (Rojas 2012). The same review describes a hormetic dose response, where low and high doses have opposite effects. This is the basis of the “mitochondrial support” claims you see online, and it comes from cells and animals, not from people taking a daily capsule.

It blocks the enzyme MAO-A

Methylene blue also inhibits monoamine oxidase A, the enzyme that breaks down serotonin, noradrenaline and dopamine (Ramsay 2007). That is the cause of the medicine interaction above. Some users think it also explains the lift they feel, but nobody has measured how strongly a 10mg dose blocks MAO-A in the body.

Hofseth’s summary is fair: most of what is known about methylene blue’s effects on the brain comes from studies in rats and in cells grown in a dish, not in people. For how it compares with other brain supplements, see our methylene blue vs other nootropics comparison, and The Methylene Blue Bible goes deeper into the mitochondrial research.

What the human brain studies found

Three small studies have measured what methylene blue does to the healthy human brain. Two point one way and one points the other.

• Attention and memory (Rodriguez 2016). 26 healthy adults aged 22 to 62 were randomised, double-blind, to a single 280mg oral dose of methylene blue (about 4mg per kg) or a placebo. One hour later, the methylene blue group showed a stronger brain-imaging response in the insular cortex during a sustained-attention task, a stronger response across several cortical areas during a short-term memory task, and 7% more correct answers when recalling information.
• Brain networks (Rodriguez 2017). The same group enrolled 28 participants and gave 280mg or a blue-dye placebo. Methylene blue lowered blood flow in a task-related network during a visual-motor task and strengthened resting-state connections between regions linked to perception and memory. Hofseth notes that this second study did not show better thinking skills.
• Blood flow and oxygen use (Singh 2023). Researchers at King’s College London gave eight healthy women methylene blue by drip at 0.5 and 1mg per kg, on separate days, against a placebo drip. Both doses cut blood flow across the brain by about 8% and lowered the brain’s oxygen use, the opposite of what the team expected. They suggest the doses may have sat above the helpful range, or that healthy brains have little room to improve.

Harvard Health points to that 2023 result as a reason to be cautious about the memory claims (Goldman 2025). The strongest case for methylene blue and the brain is the 2016 memory result. The strongest case against is that it has not been repeated in a larger trial, and the only study to measure brain energy use directly found it went down.

What none of these studies tested matters just as much:

• None of them enrolled people with brain fog.
• Each used a single dose. There is no human data here on daily use over weeks.
• The oral dose was 280mg. One of our capsules holds 10mg, which is 28 times less, and no trial has tested 10mg a day.

Methylene blue in Australia: cost per dose

Prices are from each seller’s product page, as of Sep 2026. Cost per day uses the label serve where the label gives one.

Add Methylene Blue capsules to cart · $59.99

How the others compare. Blue Brain is a stronger 1.5% solution, so each ml holds more methylene blue, and its label lists water, ethyl alcohol and potassium sorbate alongside the USP methylene blue. It suits someone who wants a concentrated liquid and is happy to work out their own measure, since the listing says “1 serve” without saying how much that is. Blootropic sells its 1% liquid for research purposes only, with no serving directions, and offers free Australian shipping over $110. Our capsules are the simplest fixed dose, and our drops are the cheapest way to take 5mg.

Want every brand side by side? Our comparison of the best methylene blue supplements in Australia covers form, dose and price across the range.

If you decide to try it

If your GP has ruled out other causes, you are clear of everything in the safety list, and you still want to see whether methylene blue helps your focus, keep the experiment small and honest:

• Stay on the label serve. One 10mg capsule a day, or 0.5 to 1ml of our 1% drops (5 to 10mg) stirred into a glass of water. The 280mg research dose is not a target for home use.
• Change one thing at a time. Don’t start methylene blue in the same week as a new supplement, a new sleep routine or a bigger coffee habit with methylene blue.
• Keep a short daily log. Note sleep, afternoon focus, mood and any side effects, and give it two weeks before you judge it.
• Stop if something feels wrong. Headaches, nausea, agitation or anything that worries you is a reason to stop and see a doctor.

Our guide to taking methylene blue drops covers measuring and timing, the liquid vs capsules comparison helps you pick a format, and the guide to microdosing methylene blue sets the small doses against the research doses in more detail.

Our pick: Eternal Elixir Methylene Blue Capsules 10mg

Eternal Elixir makes these capsules, and they are our pick for a daily methylene blue in Australia. The reasons are on the label:

• A fixed 10mg dose. Each capsule holds 10mg of pharmaceutical-grade USP methylene blue, so there is nothing to measure.
• A short ingredient list. Methylene blue, rice flour, a cellulose capsule and citric acid.
• No blue tongue. You swallow the capsule, so the dye doesn’t touch your mouth. Your urine will still change colour.
• 60 capsules for $59.99. That is $1.00 a day on the label serve of one capsule. Two bottles save 10%, three save 15% and five save 20%.
• Sydney dispatch. Orders ship from Sydney within 24 hours on business days, with a 30-day money-back guarantee, Afterpay and free shipping over $100.

Many people pair methylene blue with NMN. No trial has tested the combination, so treat it as a second experiment and add it after the first one is settled. Our NMN 500mg capsules hold 500mg per capsule, 90 capsules per bottle, and our guide to stacking methylene blue with NMN explains how people combine them. If you are still choosing an NMN, see our best NMN supplements in Australia comparison.

Who methylene blue suits, and who it doesn’t

It may suit you if

• You are a healthy adult, you take no serotonergic medicine, and you either know your G6PD status or have no family history of the deficiency.
• You want to run a careful self-experiment for focus, and you accept that the human evidence is three small single-dose studies.
• Blue or green urine won’t bother you.

It doesn’t suit you if

• You have ongoing brain fog after an illness and haven’t yet seen your doctor about it.
• You take an antidepressant or another serotonergic medicine, or you are pregnant, breastfeeding or under 18.
• You want a product with trial evidence for brain fog. No methylene blue product has that. For broader options, read our guide to the best energy supplements in Australia.

Frequently asked questions

Can methylene blue help with brain fog?

No trial has tested methylene blue in people with brain fog. The closest evidence is a single-dose study in 26 healthy adults, where 280mg led to 7% more correct answers on a memory task an hour later, and a 2023 study in which it lowered blood flow to the brain. If you are healthy and want to try it for focus, our pick is Eternal Elixir Methylene Blue Capsules at 10mg a day.

Add Methylene Blue capsules to cart · $59.99

Should I see a doctor before trying methylene blue for brain fog after COVID-19?

Yes. Nobody knows whether methylene blue helps, because it has not been tested. We found no published or registered trial of methylene blue for memory or concentration problems after COVID-19, only a 2021 letter calling for research and an eight-person pilot run during infection with no comparison group. Healthdirect says there are currently no recommended medicines for long COVID, so start with your GP.

Why do I feel so good on methylene blue?

No study has measured this at supplement doses. Two explanations come up in the research: methylene blue blocks MAO-A, the enzyme that breaks down serotonin and dopamine, and in cell and animal studies it passes electrons along in the mitochondria. Expectation plays a part too, which is why good trials compare it against a placebo. If the lift feels strong, check that nothing else you take raises serotonin.

Is it bad to take methylene blue every day?

There are no long-term trials of daily 5 to 10mg use in healthy adults, so nobody can say what months of use do. Expect blue or green urine for as long as you take it, and remember that the interaction with serotonergic medicines applies on every day you take it. Stay within the label serve and review your log every few weeks.

Why don’t doctors recommend methylene blue?

Doctors do use methylene blue, as a hospital medicine given under supervision. Their caution about daily supplements comes down to a few facts: the human evidence in healthy people is three small single-dose studies, it interacts dangerously with common antidepressants, and it is unsafe for people with G6PD deficiency. Harvard Health also warns that industrial-grade methylene blue and aquarium products are sold online too, and they should not be used in people. If you take any prescription medicine, talk to your doctor before you try it.

How long does methylene blue take to work?

In the imaging studies, changes showed up one hour after a single 280mg dose. Nobody has measured how quickly a 10mg dose acts, and at that level many people notice nothing on the first day. Judge it over two weeks with a log, not over two hours.

What is the best methylene blue supplement in Australia?

Eternal Elixir Methylene Blue Capsules 10mg are our pick, and we make them. You get a fixed 10mg USP dose, 60 capsules for $59.99 ($1.00 a day) and dispatch from Sydney within 24 hours. If you would rather adjust the dose, our 1% drops let you start at 5mg for about $0.50 a day.

Add Methylene Blue capsules to cart · $59.99

The bottom line

Methylene blue changes activity in the healthy human brain after a single large dose, and one small study found better memory scores an hour later. It has not been tested for brain fog, including brain fog after COVID-19, and one careful study found it lowered the brain’s blood flow and oxygen use. If you have lingering symptoms after an illness, see your GP first. If you are a healthy adult who wants to try it for focus, Eternal Elixir Methylene Blue Capsules give you a fixed 10mg dose for $1.00 a day. Read the safety list, keep a log, and talk to your doctor first if you take any prescription medicine.

Related reading

• Methylene blue capsules for energy, mood and focus
• Will methylene blue show up on a drug test?
• Pterostilbene vs resveratrol for longevity
• Browse the full Eternal Elixir range

Sources

• 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 Behav. 2017;11(3):640-648. PMC5018244
• Singh N, MacNicol E, DiPasquale O, et al. The effects of acute methylene blue administration on cerebral blood flow and metabolism in humans and rats. J Cereb Blood Flow Metab. 2023;43(2 Suppl):95-105. PMC10638993
• Rojas JC, Bruchey AK, Gonzalez-Lima F. Neurometabolic mechanisms for memory enhancement and neuroprotection of methylene blue. Prog Neurobiol. 2012;96(1):32-45. PubMed 22067440
• Ramsay RR, Dunford C, Gillman PK. Methylene blue and serotonin toxicity: inhibition of monoamine oxidase A (MAO A) confirms a theoretical prediction. Br J Pharmacol. 2007;152(6):946-951. PubMed 17721552
• Belfield KD, Tichy EM. Review and drug therapy implications of glucose-6-phosphate dehydrogenase deficiency. Am J Health Syst Pharm. 2018;75(3):97-104. PubMed 29305344
• Magoon R, Bansal N, Singh A, Kashav R. Methylene blue: subduing the post COVID-19 blues! (letter). Med Hypotheses. 2021;150:110574. PubMed 33799158
• Hepburn J, Williams-Lockhart S, Bensadoun RJ, Hanna R. A novel approach of combining methylene blue photodynamic inactivation, photobiomodulation and oral ingested methylene blue in COVID-19 management: a pilot clinical study with 12-month follow-up. Antioxidants (Basel). 2022;11(11):2211. PubMed 36358582
• Hofseth LJ. Is methylene blue really a brain booster? A pharmacologist explains the science. The Conversation, 3 June 2025. theconversation.com
• Goldman L. What to know about methylene blue. Harvard Health Publishing, 24 April 2025. health.harvard.edu
• Healthdirect Australia. Long COVID. healthdirect.gov.au
• ClinicalTrials.gov search: methylene blue with long COVID, post-COVID and brain fog as conditions, checked September 2026. clinicaltrials.gov
• Supplement Mart, Methylene Blue by Blue Brain product page (price, size, 15mg/ml, label ingredients), checked September 2026. supplementmart.com.au
• Blootropic, Methylene Blue 1% Liquid product page (sizes, prices, research-only statement, shipping), checked September 2026. blootropic.com