My brother is experiencing hyperthyroidism. he took too much thyroid medication and has rapid heart rate and he was experiencing chest pain. as of right now hes feeling a lot better, but still has some chest pain and tightness. ?

Time to see a doctor: Drug overdose, chest pressure, or chest pain are signs that he should talk with his doctor right away or go to the ER. In adults (less likely in teens), chest pain can be a heart attack. He should not drive himself (safer by ambulance). If it turns out not to be arrhythmia or heart attack symptoms, or anxiety attack symptoms, the ER will also have checked for problems such as a lung issues.