Our most popular vitamin C and a useful choice in an intense PD therapy plan. If you know you are highly sensitive to vitamin C, you should consider taking a buffered vitamin C that will make it easier to take doses in the 2,000 mg to 4,000 mg (2-4 gram) range. This buffered vitamin C from Douglas Laboratory will tend to protect the digestive tract from such irritation. Popular with men who use high doses of vitamin C without any problem.