Can orthomolecular medicine be fatal?

Don't know fatal. Orthomolecular medicine is a practice of optimizing health through vitamins and supplements. Some of these are at megadoses that can be toxic. The general scientific consensus is that there is little benefit. For normal individuals a balanced diet is all that is necessary. Supplementation is a waste of money. .
Not so far. Here's the comparison: about 106, 000 deaths/year from drugs. (the health plus letter february 16, 2010 vol. 8, no. 5) no deaths from vitamins in 27 years. Bronstein ac, spyker da, cantilena lr jr, green jl, rumack bh, giffin sl. 2009 annual report of the american association of poison control centers' national poison data system (npds): 27th annual report. Clinical toxicology (2010). 48, 979-1178.