If you try 25 mg and can't finish the round, then you could go back to 12.5 mg for the next round. It is up to you. If you go too slow though, it might take much longer to see progress. Since DMSA is expensive compared to ALA, some take twice as much ALA as DMSA. If you had your amalgams replaced recently though, you might want to use just DMSA for a while before adding ALA.