Sn instructed patient about Bystolic. This is a prescription medicine that belongs to a group of medicines called “beta blockers.” The most common side effects people taking Bystolic report are headache, fatigue ( tiredness ), dizziness ( if you feel dizzy, sit or lie down and tell your doctor right away ), diarrhea, nausea, insomnia ( difficulty falling or staying asleep ), chest pain, bradycardia ( slow heartbeat ), dyspnea ( shortness of breath ), rash, and peripheral edema ( leg swelling due to fluid retention ). Other possible side effects include masking ( hiding ) the symptoms of low blood sugar and hyperthyroidism ( overactive thyroid ), especially a fast heartbeat. Tell your doctor if you gain weight or have trouble breathing while taking Bystolic. Patient verbalized fair understanding .