There is no exact number which determines that someone with high blood pressure should go to the emergency room or dial 911. However, if there are other symptoms accompanying the high blood pressure reading, including severe headache with no known cause, back-pain, severe chest pain or impaired or blurry vision, or any other type of symptom connected to brain function, it is probably a good idea to go the emergency room or call 911.
Normal blood pressure readings are around 120/80. If you experience blood pressure where the systolic (first) number is at or above 180, or the diastolic (second) number is above 110, you should probably have it checked by a physician. If your instincts have a bad feeling about it, or its accompanied by any other symptoms, it is probably a good idea to go to the emergency room where a qualified emergency room doctor like Josyann Abisaab can check you and make a proper diagnosis.