Some people experience diarrhea w/ vit C. Sometimes the diarrhea is caused by a corn base to the vitamin pill, and not the vitamin C itself. Check on base.
Watch iron when using increased vit C doses, as C increases Fe absorbtion. Esp: post-menopausal women and men of northern European descent.
Bowel tolerance for vit C can change. Turnover rate adjusts.
--is dependent on location of infection: lower tolerance with GI infx, higher with resp infx.
--tolerance increases with gradual increase of dosage