Methylene blue

What the 7% actually measured

In 26 healthy adults, correct answers rose about 7% within the treated group. The change compared with placebo was not statistically significant (P=.09).¹⁰⁵⁴

A medicine with several distinct uses

The US intravenous product treats acquired methemoglobinemia, a condition that reduces the blood's ability to carry oxygen. Oral Lumeblue tablets are a diagnostic product: they color the bowel lining during colonoscopy. Research into cognition uses other settings and outcomes.^1055,1056

The cognition evidence

The acute study found changes in brain-scan activity. Reaction time did not improve significantly, and the one-week follow-up found similar mood and delayed recall between groups. A separate 12-week registry has posted results, but substantial attrition and missing comparative analyses leave daily-use benefits unresolved.^1054,1057

Alzheimer’s and mood studies

The longer studies enrolled people with specific diagnoses. An exploratory Alzheimer trial found a benefit in one severity subgroup; the mild-disease cognitive comparison was null. A bipolar crossover improved mood ratings without a significant cognition benefit.^1079,1067

Trial	What was measured
248 patients	Open-label trial in older adults having major noncardiac surgery. Delirium: 7.3% versus 24.2%.1058
217 patients	Joint replacement. Delirium: 8.3% versus 20.4%. More fever with methylene blue; similar cognition scores at one month.1059
314 patients	Pancreatic surgery. Delirium: 11.5% versus 23.6%. Single-blind trial; abstract-level evidence.1060

Reading the surgery results

These trials gave intravenous methylene blue during hospital care. The joint-replacement study followed delirium for five days. Its anesthetist knew the treatment, and urine color could reveal it to others. The longer-term cognition result was neutral.¹⁰⁵⁹

Oral MMX		56.29%
Placebo		47.81%

Patients with at least one adenoma or carcinoma detected. 2019 phase 3 trial: 273/485 versus 229/479 in these two full-analysis groups. The separate 100 mg arm is omitted from this comparison.¹⁰⁶¹

Chinese trial endpoint

A government-hosted sponsor submission reports a trial with 1,802 randomized patients. Nonpolypoid growths were detected in 51.0% versus 41.2% of the analyzed groups. Adenomas within that category were found in 39.1% versus 30.9%. The full paper and the missing participant-flow detail still need verification.¹⁰⁶²

Long-term safety

Animal studies found blood toxicity and tumor signals after prolonged exposure. IARC’s 2016 assessment could not classify the cancer risk in humans. The daily-use safety question remains open.^1078,1076

Common questions

01 Is methylene blue a peptide?

No. It is a small-molecule dye and medicine. The chloride, hydrate, reduced derivatives and different finished products have distinct chemical or product identities.^1064,1065

02 Does it improve memory by 7%?

That headline comes from 26 healthy adults in an acute experiment. Correct responses rose about 7% within the methylene-blue group, but the change compared with placebo was not statistically significant (P=.09).¹⁰⁵⁴

03 What did the brain scans actually show?

Some task-related brain activity changed after a single exposure. Reaction time did not improve significantly. Brain-scan activity and performance on a memory task are different outcomes.¹⁰⁵⁴

04 Did the effect last a week?

At one week, the trial found no significant group difference in mood ratings or delayed recall of words from a crossword puzzle.¹⁰⁵⁴

05 Has daily use actually been studied?

Yes. A 12-week cognition study posted results, but heavy attrition and missing between-group analyses leave its findings unclear. Longer Alzheimer and bipolar studies enrolled people with those diagnoses.^{1057,1079,1067}

06 What about the anxiety study people cite?

In 42 adults with claustrophobic fear, results depended on how well the exposure session went. People who finished with little fear benefited on later fear testing; those who remained more fearful tended to fare worse.¹⁰⁶⁶

07 Did it help cognition in bipolar disorder?

A six-month study in 37 people taking lamotrigine found no significant cognitive improvement. Depression and anxiety scores were separate outcomes and did improve.¹⁰⁶⁷

08 What did the newer surgery trials find?

Delirium occurred less often in trials of 217 joint-replacement patients and 314 pancreatic-surgery patients given intravenous methylene blue during surgery. In the joint-replacement trial, fever was more frequent and cognition scores one month later were similar between groups.^1059,1060

09 Can oral products cause serotonin problems too?

An oral methylene-blue-containing urinary medicine was linked to a reported serotonin-syndrome case in someone taking several serotonergic drugs. The report concerns a mixed product and cannot define a safe oral dose.¹⁰⁶⁸

10 Why is G6PD deficiency such a concern?

G6PD deficiency can make treatment ineffective and cause severe red-blood-cell breakdown. The US label lists it as a contraindication. Hemolysis has also been reported in a patient with measured normal G6PD activity.^1055,1083

11 Why do half-life estimates vary so much?

Studies used different products, assays and blood compartments. The current IV label gives about 24 hours; an older seven-volunteer study estimated 5.25 hours in whole blood. Oral MMX tablets release the drug later in the gut.^{1055,1069,1070}

12 What are the colonoscopy tablets for?

They stain the bowel lining to help clinicians find lesions. In a phase 3 trial, 56.29% of patients receiving oral MMX tablets had at least one adenoma or carcinoma detected, compared with 47.81% receiving placebo.¹⁰⁶¹

13 Did those tablets also reduce false alarms?

The EU label's strong P value tests whether the false-positive rate stayed within a prespecified margin; the 2019 trial found no significant reduction in false-positive resections.^1061,1056

14 Is it approved for brain fog?

The US ProvayBlue indication is acquired methemoglobinemia in adults and children. Brain fog and cognitive enhancement are outside that indication.¹⁰⁵⁵

15 Why can an oxygen monitor read lower after treatment?

Methylene blue can interfere with pulse oximetry and make the displayed oxygen saturation underestimate the blood measurement. The label also describes interference with some urine tests.¹⁰⁵⁵

16 Does raising blood pressure during shock improve survival?

The survival result is uncertain. Earlier reviews reported a benefit, while a 2026 review of nine randomized trials found no clear pooled short-term mortality difference. The reviews use overlapping but different trial sets; blood-pressure recovery is a separate outcome.^1071,1082

17 Which medicines are the main interaction concern?

The US label warns about medicines that affect serotonin, including antidepressants, opioids and dextromethorphan, an ingredient in some cough medicines. Medication review needs the exact product names, including nonprescription medicines.¹⁰⁵⁵

18 Does kidney disease change how the body handles it?

Yes. Exposure to the intravenous product rises as kidney function worsens. Oral MMX data in moderate or severe kidney impairment are limited. Those differences belong in a product-specific review.^1055,1056

19 What about pregnancy or breastfeeding?

The US IV label warns of fetal harm and advises interrupting breastfeeding for eight days after treatment. The EU oral Lumeblue label lists pregnancy and breastfeeding as contraindications.^1055,1056

20 Why can urine or stool turn blue-green?

Methylene blue is a dye. Blue-green urine and stool are recognized effects in the oral MMX label; skin can also look blue. A change in color alone cannot show whether a product improved cognition.¹⁰⁵⁶

21 Are online products checked as carefully as approved medicines?

Australia's regulator warned in September 2025 that unregistered oral products marketed for cognition, mood and anti-ageing had not undergone its quality, safety or efficacy assessment. That advisory does not verify any particular seller or batch.¹⁰⁷²

22 Why does one product warn about peanut or soy allergy?

Lumeblue tablets contain soya lecithin. Their EU label lists peanut or soya allergy as a contraindication. This warning concerns the finished tablet and its ingredients.¹⁰⁵⁶

23 What did the Chinese colonoscopy trial find?

A sponsor submission reports more nonpolypoid colorectal growths detected with oral MMX: 51.0% versus 41.2%. For nonpolypoid adenomas specifically, the figures were 39.1% versus 30.9%. The results came from different endpoints in the same trial.¹⁰⁶²

24 What did the Japanese safety follow-up add?

The national postmarketing survey recorded suspected drug reactions in 5 of 46 patients, including serious hemolytic anemia in 3. It followed treatment for toxic methemoglobinemia, without a comparison group.^1063,1073

25 Did the surgery benefit last a month?

In the joint-replacement trial, both groups had a median cognition score of 32 one month after surgery. The difference was not statistically significant (P=.482). Its positive finding was fewer delirium cases during the first five days.¹⁰⁵⁹

26 Has long-term daily safety been established?

The cited studies use different products, populations and durations. They leave long-term safety for routine cognitive enhancement unresolved. The oral MMX label includes laboratory and animal safety findings.^{1057,1074,1056}

27 What symptoms raised the serotonin warning?

The TGA lists muscle spasms, sweating, tremor, confusion and agitation among possible symptoms. Serotonin syndrome can be life-threatening. Suspected symptoms after a combination need urgent medical assessment.¹⁰⁷²

28 What does the combined surgery evidence show?

A 2026 review pooled the three Chinese trials already described here, covering 779 surgical patients. It reported lower odds of postoperative delirium, OR 0.35 (95% CI 0.23 to 0.53). All three trials had masking concerns, and the review is another analysis of the same patients.¹⁰⁸⁴

29 Has it been tested in Alzheimer’s disease?

Yes. An exploratory trial randomized 321 people with mild or moderate Alzheimer’s disease to a specific methylthioninium chloride formulation or placebo. One dose showed a 24-week cognitive benefit in the moderate-disease group; the mild-disease cognitive comparison was null. Small subgroups, dropout and formulation problems complicate the result.^1079,1077

30 What about depression or mood?

Older psychiatric studies reported improvement in some patients, including a short controlled depression trial. Their reporting and sample sizes limit what can be concluded. The newer bipolar crossover found improved mood ratings but no significant cognition benefit.^{1081,1085,1067}

31 What have researchers found in online product listings?

A September 2026 preprint reviewed 63 products and found that only four listings carried any of the safety warnings it checked. Five had conflicting statements. The study assessed online information, with no laboratory testing of the products.¹⁰⁸⁶

32 What is known about cancer risk?

Two-year animal studies found tumor signals and blood toxicity. IARC’s 2016 evaluation found limited evidence in animals and no human cancer data to assess, placing methylene blue in Group 3: its human carcinogenicity could not be classified. Long-term human risk is unresolved.^1078,1076

33 What did the colon-biopsy safety study measure?

Ten patients completed an oral MMX study that compared colon biopsies before and after one exposure. A marker of double-strand DNA breaks was unchanged. The registry explains that 13 people enrolled; two withdrew consent and one was excluded for altered laboratory results.^1080,1075