Vitamin C - Mayo Clinic
www.mayoclinic.org › drugs-supplements-vitamin-cNov 17, 2020 · When taken at appropriate doses, oral vitamin C supplements are generally considered safe. Taking too much vitamin C can cause side effects, including: Nausea, vomiting and diarrhea; Heartburn; Stomach cramps or bloating; Fatigue and sleepiness, or sometimes insomnia; Headache; Skin flushing