The recommended amount of vitamin C in an adult's daily dietary intake is between 65 and 90 milligrams, explains Mayo Clinic. However, up to 2,000 milligrams can be ingested by an average adult and still be considered safe.
It is possible to ingest too much vitamin C, notes Mayo Clinic. Although a large amount of vitamin C obtained through dietary sources, including oranges, broccoli and strawberries, is unlikely to cause any health problems, vitamin C supplements in large quantities can potentially lead to diarrhea, nausea and vomiting. Other side effects, such as heartburn, headache, insomnia and kidney stones, have also been reported.