I have used circO2 as a daily supplement for over five years. It is the only supplement that makes a big difference in my life. I am 72 years old and I feel forty. I use it with Perfect Amino and it leaves me very energetic. I can do walking, and I play tennis without feeling burnt out like before. For the past 2 years I started sharing it with my wife who is 71 and was suffering from muscle cramps. after a few months, she has forgotten that she had a muscular problem. Now we enjoy our activities with feeling lousily.