I use methylene blue to combat carbon monoxide (CO) and other oxidation issues. I use a drop of the aquarium solution, can mix in water or take straight. Too much ( like 60 drops of the 2% solution can be toxic ) based on weight (150lb person).
It is also good for parkinsons, alheizmers, old age dementa. etc. They are all oxidative damage. People with genetic disorders take it daily for their entire life without bad effect.
I have been taking it for about 8 years now daily. There is a genetic disorder that can affect (mostly asian people) and they can get anemia if they take it (in large doses) but that is very rare in others. It also helps with covid and certain parasites. Used for 60 years to treat malaria.