You may experience some or none of the side effects listed in this article. Unfortunately, there is no way for your healthcare provider to know beforehand if you will develop side effects from a medicine that you have never tried. Therefore, let your healthcare provider know if you develop any side effects or something that "just does not seem right" while taking Toprol-XL. While it may not be a Toprol-XL side effect, your healthcare provider should be able to diagnose and treat the problem.