What is a dangerously high blood pressure reading?

Blood pressure readings over 180 systolic or 110 diastolic are considered a medical crisis and require immediate medical attention, according to the American Heart Association. This is known as a hypertensive crisis, and symptoms can include severe headaches, anxiety, nosebleeds and shortness of breath.

A hypertensive crisis can be controlled within a few hours with the proper medication, according to WebMD. If left untreated, or if blood pressure readings continue to rise, a more dangerous emergency can set in. Symptoms of this include dizziness, confusion, chest pain, edema, severe headache, seizure and heart attack as a result of organ failure.