Most people experience no negative side effects when taking vitamin C in recommended dosages, according to WebMD. However, nausea, vomiting, heartburn, stomach cramps and headache occasionally occur, particularly in people taking large amounts of vitamin C. The recommended dietary allowances are 75 milligrams for women and 90 milligrams for men.
Large amounts of vitamin C present problems for people with certain conditions. Senior women with diabetes who take more than 300 daily milligrams are candidates for heart disease, WebMD reports. Individuals with certain blood-iron disorders should avoid large quantities of vitamin C, as it increases iron absorption. Patients with histories of kidney stones are prone to further attacks if they ingest excessive amounts of vitamin C.