Skip to main content
SupplementScience

Vitamin C Side Effects & Safety

This content is for informational purposes only and does not constitute medical advice. Consult your healthcare provider before starting any supplement. Full disclaimer

Safety Profile

Overall safety rating: Generally Safe

Potential Side Effects

  • Gastrointestinal discomfort (diarrhea, nausea, cramps) at doses above 2,000 mg
  • Increased oxalate excretion, potentially raising kidney stone risk in susceptible individuals
  • May cause false readings on certain blood glucose monitors
  • Iron overload risk in individuals with hemochromatosis due to enhanced absorption

Drug & Supplement Interactions

  • May increase iron absorption — use caution in those with hemochromatosis or iron overload
  • High doses may interfere with warfarin anticoagulant therapy
  • May reduce effectiveness of certain chemotherapy agents (consult oncologist)
  • Aluminum-containing antacids — vitamin C increases aluminum absorption

Maximum Dose

Do not exceed: 2,000 mg/day (NIH Upper Tolerable Intake Level); higher doses may cause GI distress

Full Vitamin C Guide

References

  1. (). Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews. DOI
  2. (). Vitamin C and Immune Function. Nutrients. DOI
  3. (). Vitamin C as an antioxidant: evaluation of its role in disease prevention. Journal of the American College of Nutrition. DOI
  4. (). The role of vitamin C in iron absorption. International Journal for Vitamin and Nutrition Research Supplement.