My ibs has been basiclly in control the past few weeks. The last time it was haywire, I had a cold and some very ill friends. I took the vit c 500mg and in a few hours I was in the bathroom. First I blamed the cold since everything I have used to turn into several trips to the john. Happended the next day the same. So now if my stomach is not 100% ok, I don't take the vit c and then I make sure I have eaten something with it so it is not churning in there by itself.After the above post, when this huge bottle is gone, I think I will get a smaller dosage and spread it out during the day and see if that helps.Another note: dddmy sister-in-law became nauseated after taking vit e in the am.She switched to before bed and no problem.