Methylene blue can help mitochondria keep working when the first part of their energy system is broken, but it doesn't work at all when the second part is broken.

When the first step of energy production is blocked, methylene blue can help mitochondria make energy again—but when the second step is blocked, it can't help at all.

In mice, methylene blue fixes energy problems only if they’re caused by a specific broken part (Complex I)—not if another part (Complex III) is broken. This is different from what was seen in guinea pigs.

Scientists found that a blue dye called methylene blue can help fix a broken energy system in mouse brain cells, but a related chemical called azure I can't — meaning only the original dye can jump over a specific energy block.

A chemical called Azure I, which comes from methylene blue, doesn’t fix the energy power plants in mouse brain cells—even though it’s better at blocking certain brain enzymes. This means it might work in other ways, not by helping cells make energy.

Methylene blue makes mitochondria produce more hydrogen peroxide, but if you block a specific part of the energy chain (Complex III), that extra production stops—meaning methylene blue needs that part to work.