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Does methylene blue kill cancer cells​?

Medically reviewed by Kristianne Hannemann, PharmD. Last updated on June 3, 2025.

Official Answer by Drugs.com

While not a conventional chemotherapy agent, research suggests that methylene blue can kill cancer cells under specific conditions, particularly when used as part of photodynamic therapy (PDT). Methylene blue is not currently a standard, FDA-approved cancer treatment on its own, and more clinical trials are needed.

How Methylene Blue Affects Cancer Cells

Methylene blue, a synthetic dye with a long history in medicine, has recently attracted attention for its potential role in cancer therapy. Methylene blue alone does not directly kill cancer cells in the way traditional chemotherapy drugs do. However, it shows notable anticancer effects when combined with light in a process called photodynamic therapy. Here’s how it works:

Research on Methylene Blue in Cancer Cells

Much of the research on methylene blue's direct anticancer effects has been conducted in laboratory settings (in vitro) or in animal models (in vivo). Large-scale human clinical trials are still ongoing or needed to establish its full safety and efficacy as a primary cancer treatment.

A systematic review of preclinical studies found that photodynamic therapy with methylene blue led to reductions in tumor size in models of breast cancer, and had anticancer activity against colorectal cancer, carcinoma, and melanoma. Some studies also reported benefits in ovarian cancer models, especially when methylene blue was delivered using nanoparticles to enhance its uptake by tumors.

Clinical trials are ongoing, and early-phase studies suggest that methylene blue-based PDT is safe and may improve outcomes when combined with standard treatments, such as chemotherapy for pancreatic cancer.

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Potential Risks and Side Effects of Methylene Blue

While methylene blue is generally considered safe when used appropriately, it is not without risk—especially outside of controlled medical settings.

Summary

Despite promising laboratory and early clinical results, methylene blue is not yet a standard cancer treatment. Its effectiveness appears to depend on the type of cancer, delivery method, and combination with light-based therapies. There is also variability in dosing strategies and formulations across studies, and more research is needed to establish standardized protocols and long-term safety.

Methylene blue, particularly when used in photodynamic therapy, can kill cancer cells by generating reactive oxygen species and disrupting cancer cell metabolism. It has shown effectiveness in preclinical studies against several cancer types and may enhance the effects of chemotherapy and radiation. However, methylene blue carries risks—including serious drug interactions and dose-dependent toxicity—and should only be used under medical supervision. Its role in cancer care remains investigational, and further research is necessary to clarify its safety and efficacy for broader clinical use.

References
  1. Bistas E, et. al. Updated 2023. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Accessed on June 3, 2025 at  https://www.ncbi.nlm.nih.gov/books/NBK557593/
  2. da Veiga Moreira, J., et. al. 2024. Methylene Blue Metabolic Therapy Restrains In Vivo Ovarian Tumor Growth. Cancers, 16(2), 355. https://doi.org/10.3390/cancers16020355
  3. de Almeida, D. R. Q., et. al. 2023. Necroptosis activation is associated with greater methylene blue-photodynamic therapy-induced cytotoxicity in human pancreatic ductal adenocarcinoma cells. Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 22(4), 729–744. https://doi.org/10.1007/s43630-022-00347-4
  4. Dos Santos, A. F., et. al. 2017. Methylene blue photodynamic therapy induces selective and massive cell death in human breast cancer cells. BMC cancer, 17(1), 194. https://doi.org/10.1186/s12885-017-3179-7
  5. Drugs.com. 2024. Methylene Blue Side Effects. Accessed on June 3, 2025 at https://www.drugs.com/sfx/methylene-blue-side-effects.html#other-side-effects
  6. Edvotek. 2015. Safety Data Sheet - Methylene Blue. Accessed on June 3, 2025 at https://www.edvotek.com/site/pdf/Methylene%20Blue.pdf?srsltid=AfmBOor4AIzlR3Fl7B78WKk3rmYXOvbLkjmjKCbewewtq7fpArHxYW92
  7. Macsen Labs. Methylene Blue for Cancer Therapy. Accessed on June 3, 2025 at https://www.macsenlab.com/blog/methylene-blue-for-cancer-therapy/
  8. Methylene Blue [package insert]. Updated March 2025. Zydus Pharmaceuticals USA Inc. Accessed on June 3, 2025 at https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8c56fbad-a449-4ed4-a55f-1694e4e8e26a
  9. Porat, R., Gilbert, S., et. al. 1996. Methylene blue-induced phototoxicity: an unrecognized complication. Pediatrics, 97(5), 717–721. PMID: 8628613
  10. Taldaev, A., et. al. 2023. Methylene blue in anticancer photodynamic therapy: systematic review of preclinical studies. Frontiers in pharmacology, 14, 1264961. https://doi.org/10.3389/fphar.2023.1264961

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