Metoprolol serious side effects. Call your doctor at once if you have any of these serious side effects: chest pain, pounding heartbeats or fluttering in your chest; feeling light-headed, fainting; feeling short of breath, even with mild exertion; swelling of your hands or feet; nausea, upper stomach pain, itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); easy bruising, unusual bleeding (nose, mouth, vagina, or rectum), purple or red pinpoint spots under your skin; wheezing, trouble breathing; depression, confusion, memory problems, hallucinations; or cold feeling in your hands and feet.