Dr. Peter Langsjoen, a cardiologist and biochemist, is the head of CoQ10 International, and lead investigator for many clinical trials using CoQ10. In early clinical trials, blood levels of CoQ10 in participants were monitored. However, they never saw any adverse effects of high levels of CoQ10 in the thousands of participants they followed.
They concluded that CoQ10 was very safe and that you could not take too much CoQ10. In fact, the higher the levels of CoQ10 that were found in the blood of the participants the better the results they were able to document. They no longer even do blood tests on CoQ10 no matter how much CoQ10 they give their patients or participants in the clinical trials. Therefore, it is felt by everyone that you just can't get too much CoQ10 and that it is one of the safest nutrients used today in supplementation.