Is methylene blue safe? What you need to know before trying it

Curious about methylene blue? This blue compound has journeyed from textile dye to medicine cabinet, but questions about its safety remain. Here’s what you should know before considering it.

What is Methylene Blue and How is it Used?

Methylene blue began as a clothing dye in the 1870s before becoming the world’s first lab-created medicine. Today, doctors primarily use it to treat methemoglobinemia, a rare blood disorder that reduces oxygen delivery throughout the body. This condition may cause bluish skin, fatigue, and shortness of breath.

Medical professionals also use methylene blue for several off-label purposes:

Treating vasoplegic syndrome (a type of shock during surgery)
Managing side effects from ifosfamide chemotherapy
Helping surgeons identify parathyroid glands during surgery
Visualization during sentinel lymph node mapping in cancer procedures
Treating cyanide poisoning
Longevity

Recently, some researchers and health enthusiasts have become interested in methylene blue for its potential anti-aging effects. These applications focus on its impact on mitochondria (the cell’s energy producers) and its antioxidant properties, though they remain experimental and haven’t received FDA approval.

Is Methylene Blue Safe for Regular Use?

Safety depends on several key factors:

At low doses (under 2 mg/kg of body weight), methylene blue is generally safe when administered by healthcare professionals. However, high doses (above 7 mg/kg) significantly increase the risk of side effects. Ironically, at high doses, methylene blue can actually cause methemoglobinemia—the very blood disorder it’s meant to treat.

The route of administration also matters. In medical settings, methylene blue is typically given intravenously under professional supervision. Oral and topical forms exist but have different safety considerations than the injectable version used in hospitals.

Another important consideration is product quality. Medical-grade methylene blue (such as ProvayBlue®) undergoes strict testing and quality control. In contrast, products marketed for alternative uses often lack regulation, raising concerns about their purity and safety.

Potential Side Effects

Even when used properly, methylene blue can cause various side effects:

Common side effects include blue-colored urine and stool (harmless but surprising), temporary skin discoloration, headache, dizziness, nausea, stomach pain, and confusion. These typically resolve once the medication clears from your system.

Serious side effects can include allergic reactions (hives, swelling, difficulty breathing), blood pressure changes, heart rhythm abnormalities, breathing difficulties, and in rare cases, seizures. When combined with certain medications, methylene blue can cause a dangerous condition called serotonin syndrome.

A 2021 review noted that while methylene blue has historically been considered safe, significant gaps exist in toxicological data, and the FDA has issued safety warnings about serious reactions in some patients.

Drug Interactions: A Major Safety Concern

Methylene blue’s most serious safety issue involves interactions with certain medications. It acts as a monoamine oxidase inhibitor (MAOI), which can dangerously interact with drugs that affect brain chemistry.

The FDA has issued safety warnings about combining methylene blue with:

Antidepressants (including SSRIs like Prozac and Zoloft, SNRIs like Effexor, and tricyclics)
Anti-anxiety medications
Some pain medications
Certain migraine treatments
Other MAOI medications

These combinations can cause serotonin syndrome, a potentially life-threatening condition involving confusion, fever, muscle rigidity, rapid heart rate, and in severe cases, death. The risk is significant enough that the FDA recommends stopping these medications before planned methylene blue treatment.

Who Should Avoid Methylene Blue?

Several groups should avoid methylene blue or use it only under close medical supervision:

Pregnant women: The FDA classifies methylene blue as pregnancy category X, meaning it should not be used during pregnancy due to evidence of fetal harm, including intestinal atresia and fetal death.

Nursing mothers: Methylene blue may pass into breast milk and potentially affect the infant, so it’s generally not recommended during breastfeeding.

People taking psychiatric medications: Due to the risk of serotonin syndrome, those on antidepressants or similar drugs should generally avoid methylene blue unless medically necessary.

People with G6PD deficiency: This genetic condition affects about 400 million people worldwide. Methylene blue can trigger hemolytic anemia (destruction of red blood cells) in these individuals, causing jaundice, fatigue, and potentially serious complications.

People with kidney problems: Since methylene blue can reduce renal blood flow, those with existing kidney issues should approach it with caution.

Using Methylene Blue Safely

If you and your doctor decide methylene blue is appropriate for your condition, follow these guidelines:

Only use it under medical supervision
Tell your doctor about all medications and supplements you take
Follow the prescribed dose exactly
Be alert for signs of allergic reaction or serotonin syndrome
If using non-prescription forms, research the manufacturer carefully and choose pharmaceutical-grade products

In medical settings, methylene blue dosing for methemoglobinemia is typically 1-2 mg/kg given intravenously over 5-30 minutes. The maximum cumulative dose should not exceed 7 mg/kg during a treatment cycle.

For experimental or off-label uses, appropriate dosing is less clear, making professional guidance even more important. Some practitioners recommend much lower doses for anti-aging purposes, but standardized protocols don’t yet exist.

The Bottom Line

Methylene blue serves important medical purposes when used correctly. However, it comes with significant risks, especially for certain groups and when combined with common medications.

The growing interest in methylene blue for anti-aging and other alternative uses raises additional safety concerns. While some early research shows promise in areas like cellular health and antioxidant effects, more studies are needed before these applications can be considered safe for regular use.

If you’re considering methylene blue for any reason, consult with a healthcare provider to weigh the benefits against the risks for your specific situation. Your provider can help determine if methylene blue is appropriate, what dosage might be safe, and how to monitor for potential side effects. Schedule a consultation with Heally today to discuss whether methylene blue might be appropriate for your health concerns.