Propranolol is a drug specially intended for patients with abnormal heart rhythms, heart disease, high blood pressure, certain types of tremor, as well as some types of tumor. It's very important that you talk to you health care provider before starting the treatment and discuss all the aspects of it. Tell your doctor about any medical conditions you have (such as congestive heart failure, thyroid disorder, depression, liver or kidney disease, problems with circulation, breathing disorders, heart block, low blood pressure, or diabetes), as well as any drugs you are taking, as they may be important in deciding how much you are likely to benefit from the treatment. Propranolol is tolerated well, although some side effects are still possible and can include dizziness, lightheadedness, upset stomach, difficulty sleeping, excessive tiredness, vomiting, constipation, rash, or diarrhea. The mild side effects mentioned tend to be short lived - in most cases you will see them disappear on their own. If that doesn't happen - make sure you talk to your health care provider about them right away and learn about the options you have to treat the condition you have.