Many people know of CoQ10 (or coenzyme Q10) as a supplement. What many don't seem to realize is that it is one of the substances the body needs for optimal health. However, some drugs such as cholesterol lowering drugs (statins) can interfere with the body's production of CoQ10 (the body can make it's own in small amounts).
Here's a video by a healthcare professional, with a real-life story about the negative effects of statin drugs and the link to CoQ10.
Not surprisingly, the doctor mentioned in the video did not seem to know much about the benefits CoQ10 supplements (or was simply the anti-supplements type). Some doctors simply do not know much about supplements and may not be able to offer good advice.
All the same, consulting a knowledgable doctor before beginning a supplement is still recommended.