Ascorbic acid is usually well tolerated. Large doses are reported to cause diarrhea and other gastrointestinal disturbance. Milder effects are observed with calcium salt. Large doses may result in hyperoxaluria and the formation of renal calcium oxalate calculi and ascorbic acid should therefore be given with care to patients with hyperoxaluria. Large doses have resulted in haemolysis in patients with G6PD deficiency.
The most frequent adverse effects of oral zinc gluconate are gastrointestinal and include abdominal pain, dyspepsia, nausea, vomiting, diarrhea, gastric irritation, and gastritis. These are particularly common if taken on an empty stomach, and may be reduced by giving them meals.