Mega dosing with vitamin C carries some risks.
Here's a report of a tiny old study (http://www.nytimes.com/1998/04/09/us/taking-too-much-vitamin...)
> 'The vitamin C in supplements mobilizes harmless ferric iron stored in the body and converts it to harmful ferrous iron, which induces damage to the heart and other organs,'' Dr. Herbert said in an interview.
> ''Unlike the vitamin C naturally present in foods like orange juice, vitamin C as a supplement is not an antioxidant,'' Dr. Herbert said. ''It's a redox agent -- an antioxidant in some circumstances and a pro-oxidant in others.''
This was for the relatively small amount of 500mg per day.
I haven't read the Wikipedia references, so maybe they're all trash, but (https://en.wikipedia.org/wiki/Vitamin_C_megadosage#Possible_...)
> Although vitamin C can be well tolerated at doses well above the RDA recommendations, adverse effects can occur at doses above 3 grams per day though overload is unlikely. The common 'threshold' side effect of megadoses is diarrhea. Other possible adverse effects include increased oxalate excretion and kidney stones, increased uric-acid excretion, systemic conditioning ("rebound scurvy"), preoxidant effects, iron overload, reduced absorption of vitamin B12 and copper, increased oxygen demand, and acid erosion of the teeth with chewing ascorbic-acid tablets.[25] In addition, one case has been noted of a woman who had received a kidney transplant followed by high-dose vitamin C and died soon afterwards as a result of calcium oxalate deposits that destroyed her new kidney. Her doctors concluded that high-dose vitamin C therapy should be avoided in patients with renal failure.[26]
And there is an LD50 for rats, although that's 11.9 g per kg. (6 ft adult is 85 kg, that's over a kilogram of vitamin C to reach the same level. That would be 1,000 tablets of 1,000 mg vitamin C.