[maaark]

It's possible to overdose on Vit C. Please be careful.

[raverbashing]

Not really

It might have annoying effects but you can't "overdose" (sure, getting a large dose is still not recommended)

You can overdose on some fat-soluble vitamins, notably Vitamin A. And by overdose I mean you can die from it

[uptownfunk]

It can give you the runs!

[empressplay]

Actually it's not. You just pee it out.

[KiwiCoder]

Taking large amounts (more than 1,000mg per day) of vitamin C can cause stomach pain, diarrhoea, flatulence.

Source: http://www.nhs.uk/Conditions/vitamins-minerals/Pages/Vitamin...