Methylene blue

Pronunciation: METH-i-leen-BLOO
Brand name: Provayblue
Dosage form: injection
Drug classes: Antidotes, Miscellaneous diagnostic dyes

Medically reviewed by Melisa Puckey, BPharm. Last updated on Apr 29, 2025.

What is methylene blue?

Methylene blue is an oxidation-reduction agent used to treat methemoglobinemia, a condition where hemoglobin is oxidized, impairing its ability to carry oxygen. Methylene blue works by reducing the oxidized hemoglobin, converting it back to hemoglobin so that it can carry oxygen properly again. Methemoglobinemia can lead to symptoms like cyanosis, fatigue, and shortness of breath.

When used for methemoglobinemia, methylene blue is given as an injection by your healthcare provider in a hospital or clinic.

Methylene blue  FDA approval was granted on August 4, 2026, for treating methemoglobinemia under the brand name Provayblue.

This medicine does not reverse methemoglobinemia in patients with glucose-6-phosphate dehydrogenase (G-6-PD) deficiency, and it may induce or worsen hemolysis in these patients.

Methylene blue is also called methylthioninium chloride.

Methylene blue has also been used as a diagnostic dye, for malaria, shock, cystitis, urethritis, cyanide and carbon monoxide poisoning, and ifosfamide-induced encephalopathy off-label.

Methylene blue off-label uses

Diagnostic Applications

Surgeons may use methylene blue as a dye to identify sentinel lymph nodes during cancer surgeries, such as lumpectomies or mastectomies. It's also used to evaluate or indicate lesions and other conditions during procedures.

Malaria Treatment

In the past, methylene blue has been used to treat malaria in areas with chloroquine-resistant Plasmodium falciparum strains.  

Vasoplegic Syndrome

Methylene blue has been used off-label for vasoplegic syndrome, a severe drop in blood pressure due to vasodilation that can occur during coronary artery bypass grafting. It may be used when epinephrine has not worked to stabilize blood pressure.

Ifosfamide-Induced Encephalopathy

Cancer patients undergoing chemotherapy with ifosfamide may develop neurotoxicity, leading to confusion, hallucinations, or even coma. Methylene blue may be beneficial in treating this condition, but it is ineffective when used as a preventative treatment.

Low-dose Methylene blue for Alzheimer's disease 

Methylene blue for Alzheimer’s disease is gaining attention as a potential therapy to slow cognitive decline. Researchers are studying a low-dose form known as hydromethylthionine, a specially modified version of methylene blue designed for better absorption and enhanced brain penetration when taken orally.

Clinical studies have shown that taking 4 mg of hydromethylthionine twice daily can significantly slow the progression of Alzheimer’s symptoms and reduce brain atrophy (shrinkage). This low-dose approach appears promising compared to traditional treatments.

Scientists believe that methylene blue works for Alzheimer’s disease by inhibiting the buildup of tau protein, an abnormal protein that forms tangles inside brain cells and may contribute to cognitive decline.

Hydromethylthionine is also known as LMTM (Leuco-Methylthioninium Bis(Hydromethanesulphonate)) or methylthioninium moiety. This form has been the focus of clinical trials aiming to develop new, more effective therapies for Alzheimer’s disease.

Early results suggest that low-dose methylene blue may offer a novel way to protect brain function and slow disease progression, but further large-scale studies are still needed to confirm its benefits.

Methylene Blue and Skin Aging

Researchers are exploring methylene blue as a possible ingredient in anti-aging skincare. One major cause of skin aging is oxidative damage, which can slow down collagen production and speed up its breakdown, leading to wrinkles, uneven pigmentation, and thinner skin.

Because methylene blue has antioxidant properties, scientists hope that methylene blue skin products could help protect the skin, improve its appearance, and even support wound healing. Some early clinical trials have been conducted, but this research is still in the experimental stage, and more studies are needed to confirm if or how well it works.

Methylene blue side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Tell your caregivers right away if you have:

• confusion or weakness;
• pale or yellowed skin;
• dark colored urine;
• fever; or
• high levels of serotonin in the body - agitation, hallucinations, fever, fast heart rate, overactive reflexes, nausea, vomiting, diarrhea, loss of coordination, fainting.

Common side effects of methylene blue may include:

• pain in your arms or legs;
• blue or green urine;
• altered sense of taste;
• headache, dizziness;
• sweating, skin discoloration;
• nausea; or
• feeling hot.

This is not a complete list of side effects, and others may occur. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Related/similar drugs

Warnings

You should not be treated with methylene blue if you have glucose-6-phosphate dehydrogenase (G6PD) deficiency or a severe hypersensitivity to methylene blue.

Many drugs can interact with methylene blue. Tell your doctor about all your current medicines and any you recently stopped using, especially an antidepressant.

Before taking this medicine

You should not be treated with methylene blue if you are allergic to it, or if you have:

• a genetic enzyme deficiency called glucose-6-phosphate dehydrogenase (G6PD) deficiency.

Many drugs can interact with methylene blue. Tell your doctor about all your current medicines and any you recently stopped using, especially:

• alfentanil, fentanyl;
• buspirone;
• digoxin, digitalis;
• dihydroergotamine, ergotamine;
• phenytoin;
• pimozide;
• quinidine;
• warfarin (Coumadin, Jantoven);
• an MAO inhibitor - isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, tranylcypromine, and others;
• an "SSRI" antidepressant - citalopram, escitalopram, fluoxetine, paroxetine, sertraline, Prozac, Paxil, Zoloft, and others;
• an "SNRI" antidepressant - desvenlafaxine, duloxetine, levomilnacipran, milnacipran, venlafaxine, Effexor, Cymbalta, Pristiq, and others;
• other antidepressants - bupropion, clomipramine, mirtazapine; or
• medicine to prevent organ transplant rejection - cyclosporine, sirolimus, tacrolimus.

To make sure methylene blue is safe for you, tell your doctor if you have:

• liver disease; or
• kidney disease.

Using methylene blue during pregnancy could harm the unborn baby. Tell your doctor if you are pregnant.

Do not breast-feed within 8 days after you received methylene blue. If you use a breast pump during this time, throw out any milk you collect. Do not feed it to your baby.

How is methylene blue given?

When methylene blue is used for methemoglobinemia, it is given as an IV injection. A healthcare provider will give you this injection. The IV infusion can take up to 30 minutes to complete.

Your breathing, blood pressure, oxygen levels, kidney function, and other vital signs will be watched closely while you are receiving methylene blue. Your blood will also need to be tested to help your doctor determine that the medicine is working.

You may only need to receive one dose of methylene blue. If you do need a second dose, it can be given 1 hour after your first dose.

Methylene blue will most likely cause your urine or stools to appear blue or green in color. This is a normal side effect of the medication and will not cause any harm. However, this effect may cause unusual results with certain urine tests.

 The approved intravenous dosage is 1 mg/kg administered over 5 to 30 minutes.

The recommended dosage in patients with moderate or severe renal impairment (eGFR 15-59 mL/min/1.73 m2 is a single dose of 1 mg/kg.

What happens if I miss a dose?

Because you will receive methylene blue in a clinical setting, you are not likely to miss a dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include vomiting, stomach pain, chest pain or tightness, wheezing, trouble breathing, feeling like you might pass out, fast heart rate, anxiety, confusion, tremor, dilated pupils, blue-colored skin or lips, numbness, or tingling.

What should I avoid while receiving methylene blue?

Methylene blue may cause blurred vision and may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert and able to see clearly.

For at least 24 hours after treatment with methylene blue, avoid exposure to sunlight or tanning beds. This medicine can make you sunburn more easily. Wear protective clothing and use sunscreen (SPF 30 or higher) when you are outdoors.

What other drugs will affect methylene blue?

Many drugs can interact with methylene blue, and some drugs should not be used together. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide. Tell your doctor about all medicines you use, and those you have recently used before your treatment with methylene blue.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer