The main causes of high and low blood pressure within a day are caused by physiology, pheochromocytoma, drugs, etc., as follows: 1, physiological: if slightly high or low within the normal range, changes within 5mmHg, generally do not make too much consideration, due to the human body rising, standing problems, tension can appear high and low blood pressure; 2, anxiety or neurological heart disease: if beyond the range is larger, at this time need to Consider whether the patient is suffering from anxiety or neurological heart disease, because anxiety and tension make blood pressure rise or fall suddenly, so the treatment is mainly aimed at neurological heart disease or anxiety; 3, pheochromocytoma: a few patients suffer from cell tumor but it is not clear, when tension or sudden external stimulation, blood pressure will suddenly soar to more than 200mmHg, but when the stimulation is lifted or When the stimulus is lifted or when the patient is quiet, the blood pressure may be normal or low. At this time, a detailed physical examination should be conducted to check whether there is a pheochromocytoma that causes the blood pressure to be high and low throughout the day.