Methylene Blue and Blood Pressure: What the FDA Label Warns About

If you have high blood pressure, a heart condition, or you take blood pressure medicine or other prescription drugs, ask a clinician before using methylene blue. Hospitals give methylene blue by IV to raise blood pressure in vasoplegia and shock, and a 2024 meta-analysis of randomized trials in critically ill and perioperative patients found it was associated with a higher mean arterial pressure (Pruna et al., Journal of Cardiothoracic and Vascular Anesthesia, 2024). The FDA label for the prescription product ProvayBlue is written for a different use, gives no blood pressure guidance for supplement users, and lists hypertension, palpitations, and tachycardia among other reported adverse reactions. We could not find a controlled trial of low-dose oral methylene blue with blood pressure as an outcome in healthy adults, so what it does to your blood pressure is unknown, and unknown is not the same as safe.

• Hospital use. IV methylene blue is used as an add-on when blood pressure stays dangerously low despite standard treatment. That is a monitored setting and a different situation from a supplement.
• The label. The ProvayBlue label is for acquired methemoglobinemia. It lists hypertension, palpitations, and tachycardia among other reported reactions and carries a boxed warning on serotonergic drugs and opioids.
• What is missing. The label text we fetched has no section on blood pressure medicines and no guidance for supplement users.
• Ask first if: you have hypertension, a heart condition, lung or pulmonary pressure problems, take any prescription medicine, or take an antidepressant.

Important: This article is education, not medical advice, and it does not encourage use. See our safety overview and the full adverse medications list.

Vasoplegia is a state where blood vessels widen so much that blood pressure falls and stays low, even with fluids and standard vasopressor drugs. It can happen in septic shock and after some heart surgeries. In that setting, clinicians sometimes add IV methylene blue. The reasoning is mechanical. A 2024 meta-analysis describes methylene blue as a nitric oxide production inhibitor that "exerts its vasoconstrictor property" and is used as an adjuvant for catecholamine-refractory vasodilatory shock (Pruna et al., 2024). A small human study of septic shock describes it as an inhibitor of guanylate cyclase (Weingartner et al., Brazilian Journal of Medical and Biological Research, 1999).

Human trials, critically ill patients. The Pruna meta-analysis pooled 11 randomized trials with 556 critically ill and perioperative patients. Methylene blue was associated with increased mean arterial pressure (mean difference 8.4 mmHg, 95% CI 5.01 to 11.75) and increased systemic vascular resistance, with no difference in cardiac output. The authors concluded that methylene blue reverses vasodilation in these patients and called for further adequately powered randomized trials (Pruna et al., 2024).

Human study, septic shock. In 10 patients with severe septic shock given IV methylene blue in an open, non-randomized trial, mean arterial pressure and systemic vascular resistance index rose. Pulmonary vascular resistance index also rose, and the ratio of arterial oxygen to inspired oxygen fell. The authors reported a significant increase in pulmonary vascular tone and a deterioration in gas exchange, and said further studies were needed (Weingartner et al., 1999).

Animal study. In rats, intravenous methylene blue caused a dose-dependent hypertensive effect, and at the higher doses that was followed by a reflex drop in pressure (Oktay et al., Pharmacology, 1993).

Mixed results in toxic shock. A systematic analysis of drug-induced shock (17 human cases, including overdoses of calcium channel blockers) found that 12 patients survived and 9 had hemodynamic improvement after methylene blue, while others showed no observed change. The authors concluded there was not enough evidence to recommend routine use (Warrick et al., Clinical Toxicology, 2016).

ProvayBlue is the FDA-approved prescription form of methylene blue. Per its label, it is indicated for the treatment of pediatric and adult patients with acquired methemoglobinemia and is given intravenously. It is not a supplement. We pulled the current label text from DailyMed on October 1, 2026 and searched it for cardiovascular content. Here is what is in it, and what is not.

The label also does not explain methylene blue as a blood pressure drug. Its mechanism section describes a redox conversion of methemoglobin back to hemoglobin. The nitric oxide and guanylate cyclase explanation comes from the published studies above, not from the label.

If any of the following describes you, talk to your clinician or pharmacist before you take any, with the bottle or product page in hand. This is the part of the article we most want you to read.

• You have high blood pressure, treated or untreated. Methylene blue raised mean arterial pressure in hospital patients with low pressure (Pruna et al., 2024), and the label lists hypertension among its reported adverse reactions (ProvayBlue label, section 6.1). We found no study in people with hypertension taking oral methylene blue.
• You have a heart condition, such as an irregular rhythm, heart failure, coronary disease, or a past heart attack. The label lists palpitations and tachycardia among reported reactions and describes chest tightness and ECG changes at large IV doses (ProvayBlue label, sections 6.1 and 10). We found no oral supplement study in these groups.
• You take blood pressure medicine, including ACE inhibitors, ARBs, beta blockers, calcium channel blockers, or diuretics. The label does not address them, and we found no study of oral methylene blue taken with them. What your regimen is meant to do is something only your prescriber can weigh against an unknown.
• You have pulmonary hypertension or a lung condition. In 10 septic shock patients, IV methylene blue increased pulmonary vascular resistance index and lowered the oxygenation ratio (Weingartner et al., 1999). Those patients were critically ill, so this is not a direct comparison, but it is a reason to ask.
• You take an antidepressant or other serotonergic drug, or an opioid or dextromethorphan. The label carries a boxed warning on these combinations. See our drug interactions guide and the adverse medications list.
• You use stimulants or decongestants. The label does not name ADHD stimulants or decongestants, and we found no source either way, so we will not guess. Ask your clinician or pharmacist.
• You have G6PD deficiency or have never been tested. The label contraindicates methylene blue in G6PD deficiency because of the risk of hemolytic anemia (ProvayBlue label, section 4). See our G6PD deficiency guide.

The serotonin warning matters here because blood pressure swings are one of its signs. The label says literature reports suggest methylene blue is a potent reversible inhibitor of monoamine oxidase, and that serotonin syndrome has resulted when it was combined with drugs that affect serotonin (ProvayBlue label, section 7). A laboratory study using purified human enzyme found methylene blue to be a potent inhibitor of MAO A and, to a lesser degree, MAO B, and the authors said this would be expected to account for serotonin toxicity in patients on SSRIs (Ramsay et al., British Journal of Pharmacology, 2007).

Why bring this up in a blood pressure article? Because the label lists labile blood pressure and tachycardia among the signs of serotonin syndrome. For someone who takes an antidepressant and also manages blood pressure, the risk is not just a high or low reading, it is an unpredictable one. Many people are on both kinds of medicine. Our drug interactions guide goes through the label list in detail.

At supplement doses, very little is known. The blood pressure evidence comes from three places: IV use in hospital patients, animal studies, and the label. The question most readers have, what low-dose oral use does in healthy adults, has almost no data behind it.

What we can say.

• IV methylene blue is associated with higher mean arterial pressure in critically ill and perioperative patients (Pruna et al., 2024).
• IV methylene blue raised blood pressure in rats in a dose-dependent way (Oktay et al., 1993).
• The FDA label lists hypertension, palpitations, and tachycardia among reported adverse reactions and warns about serotonergic drugs (ProvayBlue label).

What we cannot say.

• Whether a low oral amount changes blood pressure in healthy adults. On October 1, 2026 we searched PubMed for methylene blue with blood pressure or hypertension, oral, and placebo or randomized, and for methylene blue with blood pressure, healthy, and placebo. Both searches returned zero results. A broader title search for methylene blue and blood pressure returned two papers, both in rats.
• Whether it is safe for people with hypertension or heart disease. We found no human study of oral methylene blue in those groups.
• What happens with blood pressure medicines. The label is silent and we found no interaction study.
• What the oral safety data show about blood pressure. One healthy volunteer study gave single oral doses of a methylene blue tablet made for colonoscopy staining and reported mostly mild, transient adverse events, with abnormal transaminases, gastrointestinal disorders, and dysuria at 13.6 percent (Repici et al., Contemporary Clinical Trials, 2012). The abstract does not report blood pressure, and the formulation is not a supplement.

So when someone tells you a small oral amount is fine for your blood pressure, ask where the data are. For the general picture on safety, see our Is Methylene Blue Safe? post and our methylene blue side effects overview. Supplement quality also varies, which is covered in our quality red flags post.

The label describes several cardiovascular and nervous system signs in its warnings and overdosage sections. If you ever take methylene blue and notice any of these, stop and get help. Do not wait to see if it passes.

• Chest pain or chest tightness. The label lists precordial pain and chest tightness at large IV doses (ProvayBlue label, section 10).
• A racing, pounding, or irregular heartbeat. The label lists palpitations and tachycardia (section 6.1).
• Trouble breathing, or severe dizziness or fainting. The label lists dyspnea and dizziness at high IV doses and hypotension at higher single doses (section 10).
• Agitation, confusion, tremor, sweating, or fever, especially if you also take an antidepressant. These are listed signs of serotonin syndrome (section 5.1).

Call your local emergency number (911 in the US) for chest pain, trouble breathing, or fainting. For questions about an exposure, Poison Help in the US is 1-800-222-1222 and the site describes it as free and confidential at poisonhelp.org. Our overdose signs guide covers the rest of the picture.

Quality matters for any supplement, and it matters more when the person taking it has high blood pressure, a heart condition, or takes prescription medicine. If your clinician does clear methylene blue for you, they will want to know what is actually in the bottle. Look for independent third-party lab testing from a credentialed lab, not just a manufacturer-issued lab report, and make sure the results include actual content verification, with purity and dose confirmed, rather than a generic pass/fail.

Nutricel publishes finished-product lab reports for its capsule formulas, with heavy metals and microbial safety testing by independent third-party labs. View our test results on the Nutricel certifications page. A lab report tells you what is in the bottle. It does not tell you what it does to your blood pressure.

Do not use methylene blue without your clinician signing off if you:

• Have high blood pressure, or take any blood pressure medicine
• Have a heart condition, an irregular heartbeat, or pulmonary hypertension
• Take an SSRI, SNRI, MAOI, opioid, dextromethorphan, or other serotonergic medication (see the adverse medications list)
• Have G6PD deficiency, or have never been tested and are unsure
• Are pregnant, breastfeeding, or trying to conceive

This applies to every form of methylene blue, including the capsules and liquid sold by Nutricel and everyone else. We are not telling you it is safe or unsafe for your situation. We are telling you the person who knows your chart should decide.

For readers with high blood pressure, a heart condition, or blood pressure medicine, the answer is none of them until your clinician says otherwise. That includes Blue Boost, Blue Liquid, Blue Shroom, Blue Immune, Blue Renew, and Blue Remove. They all use the same methylene blue, so the same caution applies to all of them, and we are not going to rank them for blood pressure.

If your clinician does clear you, bring the product page and the lab report to that appointment. Our certs page lists the lab reports. Whether it is appropriate for you is their call.

For readers who do not have high blood pressure or a heart condition, do not take blood pressure medicine, and have cleared methylene blue with their clinician, this is how our products differ:

Blue Boost is our core formula: 12mg of methylene blue per capsule with Vitamin C Ester and organic cacao.

Blue Immune combines methylene blue with copper, NAC, grass-fed beef liver, and vitamins A, C, and E.

Blue Shroom pairs methylene blue with six organic mushroom extracts including lion's mane, reishi, cordyceps, chaga, shiitake, and turkey tail.

Blue Renew is built around GlyNAC (glycine and N-acetyl cysteine) alongside methylene blue.

Blue Remove combines zeolite, curcumin, and nattokinase with methylene blue.

Blue Liquid is USP-grade methylene blue in a dropper bottle (1%, 10mg per mL).

Methylene blue can change blood pressure. We know that from IV use in hospital patients with dangerously low pressure and from animal studies. The FDA label for the prescription product lists hypertension, palpitations, and tachycardia among reported reactions and warns about serotonergic drugs, but it was not written to answer whether a supplement is safe for someone with high blood pressure or heart disease.

What we cannot find is a controlled human study of low-dose oral methylene blue and blood pressure in healthy adults, let alone in people with hypertension or heart conditions. If you manage your blood pressure, have a heart condition, or take prescription medicine, talk to your clinician or pharmacist before using it, and treat the lack of data as a reason to wait rather than a reason to try.

FDA Label and Poison Control

Blood Pressure and Circulation Studies

Serotonin, MAO and Oral Safety

Further Reading

Sam Carlson, Marketing Developer at Nutricel

Sam is a marketing developer at Nutricel who writes the Nutricel Insights series to help our customers understand methylene blue and make informed choices, translating the published research into plain language. Sam is not a medical professional, and these articles are intended as education rather than medical advice. Every figure in this piece is tied to the studies listed in the references, and you should always speak with your healthcare provider before starting any supplement.