If you have too much vitamin C, especially from supplements exceeding 2,000 mg per day, you may experience mild to moderate side effects mostly related to digestive discomfort such as diarrhea, nausea, stomach cramps, bloating, and general abdominal discomfort. In some cases, taking excessive vitamin C for a long time can increase the risk of kidney stones due to higher excretion of oxalate in urine. Additionally, very high doses might interfere with nutrient absorption, affecting vitamin B-12 and copper levels, and could increase iron absorption. Rarely, more serious side effects like kidney damage have been reported, particularly in those with pre-existing health conditions. High intake may also cause symptoms like heartburn, headache, skin flushing, and fatigue. It is generally safe at recommended doses, but doses over the established upper limit can cause these adverse effects.
