A Closer Look at the Anticancer Properties of Methylene Blue

• Methylene blue targets different cancers — The analysis covered different types of cancer, including colorectal tumors, melanoma and carcinoma, highlighting methylene blue’s ability to shrink tumors through a highly targeted mechanism that spares healthy tissue. A total of 133 mice were used, with 59 receiving methylene blue photodynamic therapy and 74 serving as untreated controls.¹

• Antitumor properties of methylene blue — The researchers found that methylene blue significantly reduced tumor sizes in seven of the 10 studies, with reductions ranging from 12% to complete tumor elimination.

The largest effects were seen in colorectal cancer models, where tumors shrank by up to 99.9%, while some breast cancer models showed slower tumor progression rather than outright shrinkage. These results show methylene blue has strong anticancer effects, though its impact varies depending on tumor type and drug delivery method.²

• The use of light to fight cancer — Photodynamic therapy relies on methylene blue’s ability to absorb light in the 630 to 680 nanometer wavelength range. When exposed to this specific type of light, methylene blue generates reactive oxygen species (ROS), highly reactive molecules that destroy cancer cells from within.

This process selectively targets tumor cells because methylene blue accumulates in malignant tissue while sparing healthy cells. The review found that this light-activated destruction was particularly effective in skin and colorectal tumors, leading to significant tumor reduction within weeks of treatment.³

• Increased bioavailability — According to the researchers, the nano-based versions of methylene blue led to even greater tumor reduction than traditional injections. For instance, a breast cancer study using methylene blue-loaded nanoparticles resulted in complete tumor eradication.⁵

• Experiments in dosages — Tumor response also depended on the number of methylene blue treatments administered. While some studies used a single injection, others administered up to seven doses over time. More frequent treatments generally resulted in greater tumor shrinkage. For example, one carcinoma model that received seven doses showed significantly slower tumor growth compared to models that received only one or two doses.⁶

• Results are positive, but sometimes inconsistent — While methylene blue photodynamic therapy was effective in most studies, the review noted some inconsistencies. In a few cases, tumors did not shrink but instead grew more slowly than untreated tumors. This was observed in some breast cancer models, where tumor reduction was not as dramatic as in other cancers.

Researchers theorize that this variation is due to differences in how well methylene blue is absorbed in different tissue types. Some cancers may require modifications in dosing, delivery methods or additional combination therapies to enhance treatment effects.⁷

• Improved antitumor response — Beyond its ability to destroy cancer cells, methylene blue also helps enhance the immune system’s response to tumors. The meta-analysis shows that ROS generated during photodynamic therapy triggers immune activation, helping the body recognize and attack remaining cancer cells.

This immune-boosting effect likely explains why some tumors continued to shrink even after photodynamic therapy sessions ended. However, more research is needed to confirm this mechanism to help improve long-term treatment outcomes.⁸

• Safe to use — Methylene blue’s safety profile is another advantage noted in the review. Unlike chemotherapy and radiation, which cause widespread damage to healthy cells, photodynamic therapy with methylene blue resulted in minimal side effects in animal models.

The treatment selectively targeted cancerous tissue without causing significant harm to surrounding healthy cells, making it a promising option for patients who cannot tolerate conventional treatments. Additionally, methylene blue is relatively inexpensive, meaning it offers a more affordable alternative to expensive targeted cancer therapies.⁹

• Methylene blue works as a chemotherapy adjunct — The researchers used an ovarian cancer model where human tumor cells were implanted into immunodeficient mice. These particular cells were resistant to carboplatin, a chemotherapy drug commonly used to treat ovarian cancer. This resistance is a major problem in real-world treatment, as many patients eventually stop responding to standard chemotherapy.

The study compared multiple treatment groups — mice receiving methylene blue alone, methylene blue combined with carboplatin, carboplatin alone and an untreated control group. Tumors in the methylene blue group grew significantly slower than those in the control and carboplatin-only groups, demonstrating its effectiveness even against drug-resistant cancer.¹²

• Cancer cell energy production is affected — Cancer cells thrive on a dysfunctional metabolism known as the Warburg effect, which prioritizes glucose fermentation over normal oxygen-based energy production. This metabolic switch allows tumors to grow rapidly and resist many treatments.

With this in mind, the study found that methylene blue disrupted this process, forcing cancer cells to rely on oxygen-based energy production again. This shift puts immense stress on the tumor cells, making it harder for them to survive and multiply.¹³

• Mitochondrial genes are targeted — Cancer cells treated with methylene blue had lower expression of key respiratory chain genes, particularly those involved in complex IV, which is responsible for oxygen reduction.

In other words, methylene blue interfered with the tumor’s ability to efficiently process oxygen, further disrupting its energy supply. This effect was much more pronounced in cancer cells than in normal cells, reinforcing methylene blue’s selective action against tumors.¹⁴

• Virtually nontoxic — Methylene blue did not cause noticeable toxicity in the test mice. Unlike chemotherapy, which often leads to severe side effects like weight loss and immune suppression, mice receiving methylene blue maintained stable body weight and showed no signs of distress.

This is a critical advantage, as one of the biggest challenges in cancer treatment is balancing effectiveness with patient quality of life. The ability to target tumors without causing widespread damage makes methylene blue an attractive option for future therapies.¹⁵

• Contraindications of methylene blue — It is a potent monoamine oxidase type A (MAO-A) inhibitor. This means that when it is combined with a selective serotonin reuptake inhibitor (SSRI) or other serotonergic drugs, your serotonin levels can increase to dangerous levels.

Methylene blue can interact with other medications, too, including other antidepressants and antimalarials, altering their efficacy or causing adverse reactions. In addition, methylene blue is contraindicated for people diagnosed with glucose-6-phosphate dehydrogenase (G6PD) deficiency due to the risk of hemolytic anemia (a blood disorder wherein your red blood cells break down faster than your body can replace them).

• Your urine will turn blue — Be aware that methylene blue can stain your urine and occasionally, your tongue. While these effects are harmless, it will most likely surprise you when it happens.

• False pulse oximeter readings — High doses can also interfere with pulse oximeter readings, due to its light absorption properties, resulting in falsely low oxygen saturation readings.

• A note for those with kidney damage — If you have severe renal insufficiency, it would be wise to use methylene blue with caution and under close medical supervision as impaired kidney function influences how fast drugs clear from your system.

• Other side effects of methylene blue — Examples include mild and transient gastrointestinal discomfort, such as nausea and diarrhea. While rare, a wide range of allergic reactions, from skin rashes to life-threatening anaphylaxis, can also occur. Headaches and confusion have also been reported. Though less common, cardiovascular effects, such as increased blood pressure and palpitations, could also occur.

• Low doses are better — Methylene blue is better taken at small, daily doses, ranging from 5 to 15 milligrams (mg), according to Dinkov, especially for long-term use. This is the sweet spot for the diverse benefits of methylene blue without increasing your serotonin levels. High doses of methylene blue are generally reserved for therapeutic applications, and even then, it must be done under the supervision of a medical practitioner.

• Buy pharmaceutical-grade methylene blue — Out of the three, the only one you should ever use is the pharmaceutical-grade variety, ideally in solid, capsule or tablet forms. Avoid liquid solutions of methylene blue as dissolving it in water significantly decreases its effectiveness after 48 to 72 hours.

• Don’t use methylene blue for aquariums — You’ve probably seen methylene blue used in maintaining aquariums. That’s because it contains antifungal, antiparasitic and oxygen-transporting properties. While those benefits also sound enticing for therapeutic usage, this type of methylene blue often contains additional harmful contaminants, even posing serious health risks to your aquatic pets.

Never use methylene blue designed for aquariums or other animal-related applications. To protect your health, always choose pharmaceutical-grade, as it undergoes rigorous testing to confirm it is free from impurities.

• Methylene blue will help with reductive stress — Remember not to over-rely on methylene blue to achieve optimal health. In my own case, I have eliminated my regular intake of methylene blue. I find that my daily walks by the ocean are incredibly helpful in managing reductive stress naturally.

However, during times when I’m unable to take a walk by the beach, I would consider taking 5 mg of methylene blue daily, adjusting to 3 mg if I were 75 pounds lighter in weight, and doing so six days a week.