5,000 mgs. is nothing. When Linus Pauling was alive he took upwards of 30,000 mgs. a day and he lived well into his 80’s.
Here is the
MSDS for ascorbic acid. Looks like the rat LD50 is 11,900 mg/kg. So a person my size (200 lbs.) would have to ingest close to two pounds of the stuff to even have half a chance of killing themselves.