What is Methylene Blue? Understanding the Possible Uses, Benefits, and Risks

Methylene blue. It’s a medication with a strange name, and the way we use it has evolved a great deal over the years. It was originally developed as a dye to color clothing. Later, it was used by researchers as a stain for identifying bacteria and parasites. 

Other potential uses popped up over time, too. Researchers thought that if the dye highlighted bacteria and parasites, maybe it could be used to destroy them. Methylene blue was then successfully used to treat malaria. And thus, the first fully laboratory-made medication was born. 

Today, methylene blue may be used in a few different situations. Here, we’ll discuss the possible uses of methylene blue.

What is methylene blue?

Modern-day methylene blue (ProvayBlue) is a diagnostic dye and FDA-approved medication. 

As a dye, its blue color helps healthcare providers identify abnormal cells. It’s used to highlight suspicious cells during diagnostic medical procedures. It’s given as an infusion in the vein or as an injection directly into lymph nodes.

As a medication, methylene blue is used to treat various health conditions. It’s most commonly given as an infusion in your vein and is typically given for a short period of time. It’s also used orally and topically in some situations.

What is methylene blue approved to treat?

Methylene blue is FDA approved to treat a blood disorder called methemoglobinemia. This causes your red blood cells to bind to oxygen in a different way, which results in less oxygen being delivered to your organs.

Methemoglobinemia has two main causes: 

1. Certain medications and chemicals that affect red blood cells

2. Rare genetic diseases, in which someone inherits a genetic mutation that predisposes them to methemoglobinemia

Methylene blue is only approved to treat methemoglobinemia caused by certain chemicals or medications — like dapsone, some anesthetics, and others. This is known as acquired methemoglobinemia. Methylene blue has also been used to treat the kind of methemoglobinemia that some people are born with, but it’s not FDA approved for this.

Methylene blue works by helping convert red blood cells into a form that will properly carry and release oxygen. In other words, it turns oxygen-containing red blood cells back into their normal state. 

Are there any recommended off-label methylene blue uses?

Yes. Methylene blue is used off-label for other health conditions. This means it’s used for reasons that aren’t officially FDA approved. 

For safety reasons, you should never use methylene blue for these reasons unless directly recommended by your healthcare provider.

Diagnostic aid

Methylene blue can help healthcare providers identify abnormal cells in your body. The dye is absorbed in larger amounts in more rapidly-dividing cells — like cancer cells. It’s specifically been used to find gastrointestinal cancers, overactive parathyroid glands, and cancer inside of lymph nodes.

Malaria

As mentioned earlier, methylene blue has been found to be effective at treating malaria. It has also been effective when used in combination with standard artemisinin-based treatments, such as artemether-lumefantrine (Coartem). 

Nail fungus

Methylene blue may also treat nail fungus (also called onychomycosis) that has not responded to traditional treatments. Research has shown that it has been effective in combination with a type of light therapy — called photodynamic therapy — to treat nail fungus.

Shock

Shock happens when someone’s blood pressure is dangerously low. This affects blood flow to vital organs, such as your brain, kidneys, and heart. In certain types of shock, methylene blue may help raise someone's blood pressure when typical treatments (vasopressors) don’t seem to be working. 

This is also true for vasoplegic syndrome, a well-known complication of heart surgery that’s similar to shock. When used early in the diagnosis of vasoplegic syndrome, methylene blue may help raise blood pressure and lower the amount of vasopressors needed without additional side effects.

Ifosfamide-induced encephalopathy

Ifosfamide is a chemotherapy medication used for several types of cancer. Encephalopathy, a type of brain disorder, can occur in up to 40% of people who take ifosfamide. Symptoms can include confusion, hallucinations, and seizures. 

There are cases in which methylene blue has successfully treated ifosfamide-induced encephalopathy. In one small study of 38 people, it was found to be effective in up to 75% of people who needed it.

Can methylene blue treat COVID-19?

No. Methylene blue isn’t authorized or approved to treat COVID-19. It’s been studied as a possible way to treat COVID, but we don’t have much data about how well it might work.

One small early study of hospitalized people with COVID found that an oral liquid containing methylene blue, vitamin C, and n-acetylcysteine showed improvements in breathing (oxygen saturation, respiratory rate) and fewer days in the hospital.

The research on methylene blue and COVID is very preliminary. It’s not clear whether it is a safe or effective treatment for the virus.

Is methylene blue safe?

Methylene blue is generally safe when used properly. However, like many other treatments, methylene blue still has the potential to be harmful. And certain groups of people are at higher risk than others. 

Risk of serotonin syndrome 

Methylene blue has a boxed warning — the FDA’s most serious type of warning — for a risk of serotonin syndrome when used with other medications that raise serotonin levels. Serotonin syndrome is a potentially life-threatening condition that is caused by too much serotonin in the brain. Symptoms can include muscle spasms, sweating, and agitation, among others. 

You shouldn’t receive methylene blue if you’re taking medications that affect serotonin levels. Some of the more common medications that can increase your risk for serotonin syndrome include: 

• Monoamine oxidase inhibitors (MAOIs) like selegiline

• Selective serotonin reuptake inhibitors (SSRIs) like sertraline (Zoloft)

• Serotonin-norepinephrine reuptake inhibitors (SNRIs) like duloxetine (Cymbalta)

• Tricyclic antidepressants (TCAs) like amitriptyline (Elavil)

• Mirtazapine (Remeron)

• Buspirone (Buspar)

• Bupropion (Wellbutrin)

• Lithium

• Triptans and ergot derivatives, which are used to treat migraine headaches

• Prescription pain medications (like opioids)

Recreational substance use can also raise your risk for serotonin syndrome, especially amphetamines, MDMA, and cocaine.

There are many other medications that can raise serotonin levels. If you are in a situation where you may be exposed to methylene blue, such as before surgery, be sure to talk to your healthcare provider beforehand about all of the medications you take or use.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency

People with a blood disorder called glucose-6-phosphate dehydrogenase (G6PD) deficiency should not receive methylene blue. G6PD deficiency is an inherited (genetic) condition that affects the way someone’s red blood cells work. As a result, the red blood cells can be destroyed after being exposed to certain medications, foods, infections, or stress.

Methylene blue is one of these medications. It can cause severe red blood cell breakdown and anemia in people with G6PD deficiency. 

Pregnancy or nursing

Methylene blue has the potential to cause harm to your developing baby. In general, methylene blue use should be avoided during pregnancy. It may also transfer into breast milk, so it should also be avoided if you’re nursing a child.

Is methylene blue being studied for any other uses?

Researchers are looking into whether methylene blue can benefit other health conditions. This includes:

• Alzheimer’s disease: Researchers are looking into hydromethylthionine’s (a chemical made from methylene blue) potential to slow memory loss in people with Alzheimer's dementia.

• Anti-aging: Even outside of dementia, methylene blue’s antioxidant activity is being investigated. Some researchers are looking to see if it can help slow damage to the skin or improve age-related memory.

• Lyme disease: In a lab, methylene blue was effective at killing antibiotic-resistant bacteria that cause Lyme disease. 

• Chemotherapy and radiation-induced mouth sores: Small studies suggest that methylene blue-based mouth rinses may help reduce mouth sore-related pain (mucositis) caused by chemotherapy and radiation.

Keep in mind: Although methylene blue’s anti-aging effects may seem exciting, this use is considered investigational. Over-the-counter methylene blue products aren’t regulated by the FDA, either. Safe and effective doses have not been established for this purpose.

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Written by:

Rachel Feaster, PharmD, BCOP, BCPS

Rachel Feaster has over 10 years of professional experience in ambulatory, inpatient, pharmacogenomics, and oncology care. She is board certified in oncology and pharmacotherapy.

Edited by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Reviewed by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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