Although its rare, some people do suffer side effects if they have too much magnesium in their system. There are usually other factors like current meds and heath issues, but to be safe, please consult your doctor before continuing and bring the bottle with you. Anything you take, vitamins, herbs, all natural supplements etc have an effect, so we buy them, but I caution you that just because it is sold over the counter doesn't mean it's harmless:)