HEALTH EXPLAINER — Methylene blue is a dye with medical applications, including treating methemoglobinemia, a condition that interferes with blood’s ability to carry oxygen. Its clinical role does not make online wellness claims proven.

Harvard Health’s reviewed explainer describes claims about memory, focus and aging as inconclusive. Medical supervision and pharmaceutical-grade formulations matter; industrial dyes and aquarium products are not substitutes.

Drug interactions deserve attention

The U.S. prescribing information for injectable PROVAYBLUE warns of serotonin syndrome when used with serotonergic medicines and opioids. Some reported cases have been fatal. The label also contraindicates its use in people with G6PD deficiency because of the risk of severe red-blood-cell damage.

Those warnings concern a specific injectable medicine. They should not be used to invent a safe dose for unregulated oral products.

Anyone considering methylene blue should discuss the exact product and their medications with a pharmacist or clinician. Do not stop prescribed medication to accommodate a supplement.

This is an explainer, not a report of a newly approved wellness treatment.

Sources: Harvard Health, April 24, 2025; FDA prescribing information.

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