I took 4000 mg per day for a solid week (I'm 200 pounds) Dr. clark says there is no harm in CQ10. She is more concerned with the capsules that some brands offer. If the capsules you are using are made from toxic chemicals and you choke down 100 of them, there is the harm. The Q10 from the Dr.Clarke store is suppose to be made from safe capsules, and I believe each pill is 400mg, so you have to take a lot less pills.