Tramadol is a prescription opioid that is prescribed to treat moderate to severe pain. Overdose can happen if taken in large quantities or with other central nervous system depressants such as alcohol or benzodiazepines. Signs of tramadol overdose are severe drowsiness, confusion, slow or shallow breathing, seizures, nausea, vomiting, loss of consciousness, and blue skin or lips from insufficient oxygen. Medical attention is important if an overdose is suspected.