Key takeaways:
Methylene blue is a laboratory-made dye that has had a variety of different uses in medicine over the years.
As a medication, methylene blue is FDA approved to treat a health condition called methemoglobinemia, a type of blood disorder. It's also sold as a dietary supplement and is sometimes used off-label for other reasons.
Methylene blue has certain risks to keep in mind. You should avoid it if you take serotonin-raising medications or if you have a glucose-6-phosphate dehydrogenase (G6PD) deficiency.
Methylene blue: It’s a medication with an unusual 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. 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 comes as both a prescription medication and an over-the-counter (OTC) dietary supplement. Here, we’ll dive deeper into methylene blue benefits and safety considerations.
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 professionals identify abnormal cells during diagnostic medical procedures. It’s given as an infusion into the vein (IV infusion) or as an injection directly into the lymph nodes.
As a medication, methylene blue is used to treat various health conditions. It’s most commonly given as an IV infusion and is typically given for a short period of time.
What is methylene blue approved to treat?
Methylene blue is approved to treat a rare blood disorder called methemoglobinemia. This condition causes red blood cells to bind to oxygen in a different way, which results in less oxygen being delivered to the organs.
Methemoglobinemia has two main causes:
Certain medications and chemicals that affect red blood cells
Rare genetic diseases, in which people inherit a genetic mutation that predisposes them to methemoglobinemia
Methylene blue is only approved to treat methemoglobinemia caused by certain chemicals or medications such as dapsone and some anesthetics. 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 purpose.
Methylene blue works by helping convert affected red blood cells into a version that will properly carry and release oxygen.
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 in ways that aren’t officially FDA approved.
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For safety reasons, you should never use methylene blue for these purposes unless directed by a healthcare professional.
Diagnostic aid
Methylene blue can help medical professionals identify abnormal cells in your body. The dye is absorbed in larger amounts in more rapidly dividing cells — such as 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’s 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 at treating nail fungus when used in combination with a type of light therapy called photodynamic therapy.
Shock
Shock happens when someone’s blood pressure is dangerously low. This affects blood flow to vital organs, such as the brain, kidneys, and heart. In certain types of shock, methylene blue may help raise a person’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.
Is methylene blue being studied for any other uses?
Researchers are looking into whether methylene blue benefits other health conditions. These include:
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-related dementia.
Anti-aging: Even outside of dementia treatment, 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 issues.
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 pain from mouth sores (mucositis) caused by chemotherapy or radiation.
Keep in mind all these uses are still experimental. But because of all the buzz around these early research findings, more people have become interested in methylene blue as a supplement for general wellness.
Methylene blue supplements
Methylene blue is also sold as a dietary supplement. It’s available as IV infusions, oral formulations, and skin creams. These products often claim to boost energy, improve memory, or support healthier aging. But experts don’t recommend that people take methylene blue supplements.
First of all, it can lead to harmful side effects and serious health issues. And secondly, supplements aren’t regulated the same way as prescription medications. This means the quality and doses of these products can vary by a wide margin. Many supplements don’t fully list the product information, and some may contain ingredients that aren’t on the label.
What’s more, safe and effective doses haven’t been established for methylene blue supplements.
What are the side effects of methylene blue?
Like many medications, methylene blue can cause side effects. Some people may notice mild reactions, such as:
Headaches
Diarrhea
Nausea
Sensitivity to light
Blue skin or body fluids
More serious methylene blue side effects can happen, too. Methylene blue can affect the nervous system and may cause confusion, restlessness, or shaking in some people. In rare cases, it can lead to heart rhythm changes or high blood pressure. If you notice any sudden or unusual symptoms after receiving methylene blue, reach out to a healthcare professional right away.
Is methylene blue safe?
Methylene blue is generally safe when used properly and under the supervision of trained medical professionals. 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 other effects.
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 (Emsam, Zelapar)
Selective serotonin reuptake inhibitors (SSRIs) like sertraline (Zoloft)
Serotonin and norepinephrine reuptake inhibitors (SNRIs) like duloxetine (Cymbalta)
Tricyclic antidepressants (TCAs) like amitriptyline
St. John’s wort
Mirtazapine (Remeron)
Buspirone
Bupropion
Lithium
Triptans and ergot derivatives, which are used to treat migraine headaches
Opioid pain medications
Recreational substance use can also raise your risk for serotonin syndrome, especially when it involves amphetamines, MDMA, or cocaine.
There are many other medications and substances that can raise serotonin levels. If you foresee being in a situation where you may be exposed to methylene blue, such as before surgery, be sure to talk to your healthcare professional beforehand about all of the medications you take.
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 a person’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 a developing baby. In general, methylene blue should be avoided during pregnancy. It may also transfer into breast milk, so it should also be avoided if you’re nursing (breastfeeding).
Frequently asked questions
There’s no recommended supplement dose for methylene blue. The only approved medical doses are given by healthcare professionals in a hospital or clinical setting. Because of the risk of potentially serious side effects, it’s best to avoid taking or applying methylene blue unless your healthcare professional specifically tells you how to use it.
Yes, methylene blue has many possible drug interactions. It should never be combined with medications that raise serotonin levels, such as SSRIs, SNRIs, or MAOIs. If your healthcare team is recommending treatment with methylene blue, be sure they know about all of the medications and supplements you take.
Methylene blue’s onset time depends on why it’s being used. When methylene blue is given for methemoglobinemia, it usually starts to work within 1 hour, and oxygen levels often improve quickly. For other uses, the timeline can vary. Your healthcare professional can explain what to expect based on your situation.
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. 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.
There’s no recommended supplement dose for methylene blue. The only approved medical doses are given by healthcare professionals in a hospital or clinical setting. Because of the risk of potentially serious side effects, it’s best to avoid taking or applying methylene blue unless your healthcare professional specifically tells you how to use it.
Yes, methylene blue has many possible drug interactions. It should never be combined with medications that raise serotonin levels, such as SSRIs, SNRIs, or MAOIs. If your healthcare team is recommending treatment with methylene blue, be sure they know about all of the medications and supplements you take.
Methylene blue’s onset time depends on why it’s being used. When methylene blue is given for methemoglobinemia, it usually starts to work within 1 hour, and oxygen levels often improve quickly. For other uses, the timeline can vary. Your healthcare professional can explain what to expect based on your situation.
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. 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.
The bottom line
Methylene blue is a medication and laboratory-made dye that has been repurposed for many different uses. It’s available as both a prescription medication and an over-the-counter supplement. However, it’s only FDA approved to treat acquired methemoglobinemia.
Do not take methylene blue supplements without the recommendation of a qualified medical professional. The risk of serious side effects is particularly high for people who are pregnant or nursing, take medications that raise serotonin levels, or have a glucose-6-phosphate dehydrogenase (G6PD) deficiency.
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