There are 2 variations of CoQ 10. 1. is called ubiquinone which as our bodies age becomes less bioavailable to people over 40. It doesn't matter how much you take it is just that the body cannot metabolize it like when we were younger. Younger adults and children absorb ubiquinone and metabolize into ubiquinol which is then metabolized 2. is called Ubiquinol. This ie fermented CoQ10 developed in Japan. years ago. Studied in Japan proved it was useful in heart disease. What is the difference with ubiquinol is that it is by far more bioavailable. Ubiquinol is more expensive due the it having to be fermented but it is by far a superior version of CoQ10. There are no upper limits to ubiquinol. So it can be taken in lager doses. I take 600 mg of ubiquinol at day.