The therapeutic dose of methylene blue is typically less than 2 mg/kg. Doses greater than 7 mg/kg increase adverse effects.

Methylene Blue (Methylthioninium chloride) is a synthetic dye first prepared in 1876. It appears as a dark green powder that produces a blue solution in water.  It's used as a redox indicator, turning blue in an oxidizing environment and colorless in a reducing environment.  It has a maximum light absorption near 670 nm and acts as a photosensitizer.  It has various medical and diagnostic applications, including FDA-approved treatment for methemoglobinemia. It's also used in various other applications, such as a milk freshness test, in aquaculture, sulfide analysis, water testing, and biological staining.  "Redox Blue" is a brand that markets Methylene Blue supplements.