Methylene blue makes heart cell power plants produce more harmful molecules when using one fuel (glutamate/malate), but less when using another (succinate), showing its effect depends on what the cell is burning.

Adding a tiny amount of methylene blue to heart cell power plants makes them use oxygen more efficiently, no matter what fuel they're burning.

A tiny amount of methylene blue helps heart cells make energy better, but too much actually hurts them — it’s a classic case of 'less is more'.

The more methylene blue you add, the more hydrogen peroxide the mitochondria make—up to 25 times more at the highest dose tested.

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.

Two chemicals, methylene blue and azure I, make mouse brain cells produce a lot more hydrogen peroxide — over two and a half times more in some cases — when tested in a lab dish. This suggests they cause the tiny energy factories inside the cells to make more of this potentially harmful substance.