http://www.drweil.com/drw/u/ART03367...Q10-CoQ10.html
Actually, it's B12 that you can't get too much of, unless you have a synthesizing problem in that pathway or with your liver. Do a separate post and ask Mrs. D if you don't believe me about the B6 and B complex.
DHEA is a hormone made from the adrenal gland. Too much DHEA might increase your risk for certain cancers. Again, this is best discussed with a primary doctor, endocrinologist, gynecologist or hormone specialist.