What are the effects of vitamin c overdose?

Inconsequential : Vitamin c is water soluable, therefore amounts taken in excess of dietary needs are quickly excreted by the kidneys. Thus vitamin c has a very low toxicity. In rat studies the ld50 (dose that kills 50%) is very high. We have no data in humans to compare. One might expect diarrhea and/or abdominal cramping but nothing dangerous. If intentional overdose seek, psychiatric care immediately.

Stomach irritation: The most common side affect of too much vitamin c is stomach irritation and diarrhea. If this continues the there could be dehydration and electrolyte imbalance. Usually ceasing the intake of extra vitamin c stops this. Also, there may be a chance of kidney stones if the person has a history of kidney stones. Talk to your physician about your specific vitamin c needs.