Does Methylene Blue Lower Blood Pressure? 2026 Research

If you have read that methylene blue lowers blood pressure, or worried that it might raise yours, the published research gives a fairly clear answer about injected doses and almost no answer about supplement doses. This guide explains how methylene blue acts on blood vessels, what the hospital studies found, what has and has not been studied in healthy people, and who should talk to a doctor before taking it.

NooBlue sells methylene blue capsules, gummies and drops, so we have a commercial interest in this topic. The figures below come from peer-reviewed studies and the prescription drug label, all linked in the sources. For the wider safety picture, see our methylene blue side effects guide.

Does Methylene Blue Lower Blood Pressure? The Short Answer

No. Methylene blue narrows blood vessels by blocking the nitric oxide signal that normally relaxes them, so its direct effect is to push blood pressure up. That is exactly why intensive care teams inject it when a patient’s blood pressure has collapsed and standard drugs are not enough. The effect is well documented at injected doses, which in hospital use range from 1 to 7.5 mg/kg (Gillman, 2011). Even the lowest of those, 1 mg/kg, is 70 mg for a 70 kg adult, delivered straight into a vein.

Supplement use is a different situation. A 5 mg capsule is one fourteenth of that lowest injected amount, and it is swallowed rather than injected. No published study has measured blood pressure in healthy people taking 5 to 10 mg a day, so nobody can honestly tell you it has no effect, or that it has a particular effect, at that dose.

How Methylene Blue Affects Blood Vessels

Blood vessels relax through a chain of signals. Cells lining the vessel release nitric oxide, which switches on an enzyme called soluble guanylate cyclase in the muscle of the vessel wall. That enzyme makes cyclic GMP, which relaxes the muscle, widens the vessel and lowers pressure.

Methylene blue interferes with this chain at two points. A 2024 review in Critical Care describes it as an inhibitor of soluble guanylate cyclase, the key enzyme in the nitric oxide pathway in vascular smooth muscle (Arias-Ortiz and Vincent, 2024). It also inhibits nitric oxide synthase, the enzyme that makes nitric oxide in the first place, and a 2012 review attributes its cardiovascular effects in septic shock to that action (Rojas et al., 2012). The same review notes that injected methylene blue can release serotonin from blood platelets. With less nitric oxide signaling, vessel muscle stays contracted and pressure rises. A 2020 review in the American Journal of the Medical Sciences traces how nitric oxide drives the extreme vessel relaxation of septic shock and how methylene blue counters it (Saha and Burns, 2020).

That is the opposite of how many blood pressure medicines work. For the rest of methylene blue’s actions, including its better-known role in mitochondria, see our explainer on how methylene blue works.

What the Research Shows: Hospital Doses Raise Blood Pressure

The strongest human data comes from intensive care and heart surgery, where methylene blue is used for vasoplegia, a state in which blood vessels are so relaxed that blood pressure falls dangerously.

• 2024 meta-analysis (11 trials, 556 patients). In critically ill and surgical patients, methylene blue was linked to a rise in mean arterial pressure of 8.4 mmHg (95% CI 5.01 to 11.75) and higher systemic vascular resistance, with no change in cardiac output. Mortality was lower in the methylene blue groups (risk ratio 0.60), and the authors called for larger trials to confirm it (Pruna et al., 2024).
• 2026 meta-analysis (9 trials, 535 patients). A newer analysis of adults in shock, mostly septic shock, found no significant reduction in short-term mortality, although several trials reported faster hemodynamic improvement and less need for other vasopressors (Rodríguez-Lima et al., 2026).
• Expert caution. The 2024 Critical Care review concluded that, more than 25 years after the first trials in septic shock, the safety and benefits are still not fully established and it should not be used routinely until more evidence is available.

The dose-response is not a straight line either. In septic shock patients, an intermediate dose of 3 mg/kg tended to improve vascular resistance and oxygen uptake more than either 1 mg/kg or 7 mg/kg, a hormetic pattern described in the Rojas review. For reference, the prescription injection’s label dose is 1 mg/kg given into a vein (ProvayBlue label), and the label lists high blood pressure among reported reactions to methylene blue class products.

What About Healthy People Taking Low Oral Doses?

This is where the evidence runs out. Animal data suggests the pressure effect is strongest when the nitric oxide system is overactive, as it is in shock. In anesthetized rats, a 3 mg/kg injection produced a brief rise in blood pressure. In rats given a bacterial toxin to mimic septic shock, a more sustained rise followed, while in control rats there was no lasting change in blood pressure (Paya et al., 1993).

In people, we found no published study that measured blood pressure after 5 to 10 mg of oral methylene blue. What is known is how the body handles a swallowed dose: in 16 healthy volunteers, the average absolute bioavailability of oral methylene blue was 72.3% measured in plasma (Walter-Sack et al., 2009), while an earlier study measuring whole blood found much lower exposure after oral than after injected doses and more of the drug in the gut wall and liver in rats (Peter et al., 2000). Our methylene blue research statistics page lays out these numbers in full.

The honest summary: a much smaller oral dose should produce a much smaller effect on blood vessels than a hospital injection, but “should” is an expectation, not a measurement. If blood pressure matters to you, measure it.

Will Methylene Blue Make Your Blood Pressure Go Up?

It depends on the situation:

• Injected in hospital: yes, that is its purpose in shock, and the trials above show a rise of several mmHg in mean arterial pressure.
• Swallowed at supplement doses: unknown, because it has not been measured. Any effect is likely to be much smaller than with injection.
• Combined with serotonergic medicines: this is the dangerous case. Methylene blue is a potent reversible inhibitor of MAO-A (Ramsay et al., 2007), and with SSRIs, SNRIs, MAO inhibitors or opioids it can cause serotonin syndrome, which can include a sharp rise in blood pressure with fever, agitation, tremor and a racing heart. A review found that 13 of 14 reported cases of methylene blue nervous-system toxicity were serotonin toxicity (Gillman, 2011). Read our guide to methylene blue and serotonin syndrome.
• If you have unexplained high blood pressure, see a doctor first: one case report describes severe, persistent high blood pressure after methylene blue was given during surgery to a 75-year-old woman who was then diagnosed with a pheochromocytoma, an adrenal tumor that releases adrenaline (Shukla et al., 2019). It is a single case, but it shows why a medical check comes before any trial of methylene blue in that situation.

Methylene Blue and Blood Pressure Medicines

Because methylene blue works against the nitric oxide pathway, it could in theory blunt medicines that rely on that pathway, such as nitrates and PDE5 inhibitors. We found no study of these combinations at supplement doses, so this is a reason for caution rather than a measured interaction. Other blood pressure medicines work through different routes, but that does not mean an interaction is impossible. If you take any blood pressure or heart medicine, ask your prescriber before adding methylene blue.

The same logic applies to nitric oxide supplements such as L-citrulline or beetroot nitrate. They aim to raise nitric oxide signaling, and methylene blue damps it, so in theory the two pull in opposite directions. That has not been tested in people. Our guide to what not to take with methylene blue and our full list of methylene blue interactions cover the medicines that matter most.

Who Should Be Cautious

• Anyone taking serotonergic medicines (SSRIs, SNRIs, MAO inhibitors, opioids and similar): do not combine them with methylene blue. The prescription injection carries a boxed warning of serious or fatal serotonin syndrome with these drugs.
• People with G6PD deficiency: the label lists it as a contraindication because of the risk of hemolytic anemia. See our page on methylene blue and G6PD deficiency.
• Anyone pregnant or breastfeeding: the label warns of possible harm in pregnancy and advises stopping breastfeeding during and for up to 8 days after a dose.
• People with high blood pressure that is not controlled, a heart condition, or blood pressure that rises for no clear reason: get medical advice first. Adding anything that can narrow blood vessels is a question for your doctor.
• People taking blood pressure, heart or nitrate medicines: ask your prescriber before starting.

Our guide to who should not take methylene blue covers every group in more detail.

A Practical Approach If You Take Methylene Blue

• Know your baseline. If blood pressure matters to you, take morning readings with an upper-arm cuff for a week or two before you start, so you have something to compare against.
• Start at the low end. Our 5 mg methylene blue capsules are one a day with food, 5 mg of USP-grade methylene blue with 10 mg of vitamin C. Our 1% methylene blue drops give 0.5 mg per drop if you want finer steps, and our methylene blue gummies contain 10 mg each. The methylene blue dosage guide explains how people choose a dose.
• Re-check after two weeks. Compare your readings with your baseline. If they are consistently higher, stop and talk to your doctor.
• Take it earlier in the day. Our guide to the best time to take methylene blue covers timing.
• Tell clinicians you take it. The drug label notes that methylene blue in the blood can make a pulse oximeter under-read oxygen saturation, which matters before any procedure.

Why Don’t Doctors Recommend Methylene Blue?

Doctors use injected methylene blue for specific hospital problems, but most do not recommend it as a daily supplement. The main reasons are thin human evidence for supplement uses and a real interaction risk with common antidepressants. A Harvard Health Publishing article makes the point that short-term use of a pharmaceutical-grade product under medical supervision is different from buying a supplement online and taking it every day (Harvard Health). Even for its hospital use in septic shock, experts say the evidence is not yet strong enough for routine use. Our overview of methylene blue benefits sets out what the research does support.

Frequently Asked Questions

Does methylene blue raise or lower blood pressure?

It raises it, at least at injected hospital doses. It blocks the nitric oxide signal that relaxes blood vessels, and a 2024 meta-analysis found a rise in mean arterial pressure of 8.4 mmHg in critically ill and surgical patients. No study has measured the effect of 5 to 10 mg taken by mouth, so do not assume it has none.

Can I take methylene blue if I am on blood pressure medication?

Ask your prescriber first. Methylene blue works against the nitric oxide pathway, so it could in theory blunt nitrates and PDE5 inhibitors, and no study has tested these combinations at supplement doses. Other blood pressure medicines work differently, but an interaction cannot be ruled out. Never combine methylene blue with serotonergic medicines such as SSRIs or SNRIs.

Does methylene blue interact with L-citrulline or beetroot?

In theory they work against each other. L-citrulline and beetroot nitrate aim to raise nitric oxide signaling, and methylene blue blocks the enzyme that nitric oxide switches on. That combination has not been tested in people. If you use them for blood flow or exercise, discuss the stack with your doctor.

Can methylene blue help with low blood pressure?

Only in the hospital sense: injected methylene blue is used in shock when blood pressure has collapsed and standard drugs have not worked. There is no evidence that oral supplements help with everyday low blood pressure or dizziness on standing. See a doctor to find the cause rather than trying a supplement.

Is methylene blue hard on your heart?

In the hospital meta-analysis, methylene blue raised vascular resistance with no change in cardiac output. We found no evidence about the heart at supplement doses in healthy people. If you have a heart condition, high blood pressure that is not controlled, or take nitrate medicines, ask your cardiologist before taking it. Serotonergic medicines are a firm no.

Does methylene blue affect pulse oximeter readings?

Yes. The drug label notes that methylene blue in the blood can cause a pulse oximeter to underestimate oxygen saturation. It is a measurement effect of the dye, not a real drop in oxygen, but tell any clinician you have taken it, especially before a procedure.

The Bottom Line

Methylene blue does not lower blood pressure. At injected hospital doses it raises it, which is why it is used in shock, and the latest analyses still debate how much that improves survival. At supplement doses the effect on blood pressure has not been measured, so if your blood pressure matters, check it before and after you start. The risk that matters most is an interaction: never combine methylene blue with serotonergic medicines, and talk to your doctor first if you take blood pressure or heart medicines.

More from NooBlue: methylene blue half-life, methylene blue and caffeine, is methylene blue safe to take daily, the NooBlue shop and about NooBlue.

This article is for general information and is not medical advice. Talk to your doctor before starting methylene blue, especially if you take prescription medicine.

Sources

1. Pruna A, Bonaccorso A, Belletti A, et al. Methylene blue reduces mortality in critically ill and perioperative patients: a meta-analysis of randomized trials. Journal of Cardiothoracic and Vascular Anesthesia. 2024;38(1):268-274. PubMed 37880041
2. Rodríguez-Lima DR, Rodríguez-Villegas A, Toro Egas JD, Bautista EMC. The effectiveness of methylene blue in adult shock: a systematic review, meta-analysis, and trial sequential analysis of randomized controlled trials. Journal of Clinical Medicine. 2026;15(12):4481. PubMed 42355649
3. Arias-Ortiz J, Vincent JL. Administration of methylene blue in septic shock: pros and cons. Critical Care. 2024;28(1):46. PubMed 38365828
4. Saha BK, Burns SL. The story of nitric oxide, sepsis and methylene blue: a comprehensive pathophysiologic review. American Journal of the Medical Sciences. 2020;360(4):329-337. PubMed 32631574
5. Rojas JC, Bruchey AK, Gonzalez-Lima F. Neurometabolic mechanisms for memory enhancement and neuroprotection of methylene blue. Progress in Neurobiology. 2012;96(1):32-45. Full text
6. Paya D, Gray GA, Stoclet JC. Effects of methylene blue on blood pressure and reactivity to norepinephrine in endotoxemic rats. Journal of Cardiovascular Pharmacology. 1993;21(6):926-930. PubMed 7687718
7. Walter-Sack I, Rengelshausen J, Oberwittler H, et al. High absolute bioavailability of methylene blue given as an aqueous oral formulation. European Journal of Clinical Pharmacology. 2009;65(2):179-189. PubMed 18810398
8. Peter C, Hongwan D, Küpfer A, Lauterburg BH. Pharmacokinetics and organ distribution of intravenous and oral methylene blue. European Journal of Clinical Pharmacology. 2000;56(3):247-250. PubMed 10952480
9. Ramsay RR, Dunford C, Gillman PK. Methylene blue and serotonin toxicity: inhibition of monoamine oxidase A (MAO A) confirms a theoretical prediction. British Journal of Pharmacology. 2007;152(6):946-951. PubMed 17721552
10. Gillman PK. CNS toxicity involving methylene blue: the exemplar for understanding and predicting drug interactions that precipitate serotonin toxicity. Journal of Psychopharmacology. 2011;25(3):429-436. PubMed 20142303
11. Shukla S, Zhu R, Rubin P, Deshpande R. Perioperative hypertensive urgency after methylene blue in a patient with undiagnosed pheochromocytoma: a case report. A&A Practice. 2019;12(9):321-324. PubMed 30431442
12. ProvayBlue (methylene blue) injection, prescribing information, revised 2/2024. DailyMed
13. Goldman L. What to know about methylene blue. Harvard Health Publishing. health.harvard.edu
14. NooBlue product pages (label amounts and directions), read Sep 2026. nooblue.com/shop