What it is
A phenothiazine dye with a long history of medical use. Available as a sterile injectable solution (ProvayBlue) and as a chemical reagent in various oral preparations.
How it works
At low concentrations, reduces methemoglobin to hemoglobin by accepting electrons from NADPH via NADPH-methemoglobin reductase. Also inhibits monoamine oxidase and modulates mitochondrial electron transport.
Where it's used
Used clinically as an injection for acquired methemoglobinemia. Studied in research for various applications including infection and neurodegeneration.
FDA-approved use
Treatment of pediatric and adult patients with acquired methemoglobinemia (intravenous injectable form).
Tracking it
Methylene Blue is oral, which makes consistency the whole game — a simple daily check-off with a reminder beats memory every time. with a half-life of about 5 hours, a dose log also lets a tracker model the relative amount still in your system between doses.
Source
OpenFDA
Last reviewed 2026-06-11