High blood pressure suddenly normal, the first thing to see if there is no medication, after taking medication blood pressure down is normal. There is no disease caused, such as heart problems, heart attack blood pressure will drop; pulmonary embolism, blood pressure will also drop; tension pneumothorax causes blood pressure will also drop; shock such as infectious shock, severe pneumonia blood pressure will also drop. There is also postprandial hypotension, some elderly people after eating due to overeating, a large amount of blood flow to the stomach, appear dizziness, no energy, measuring blood pressure will even be too low; postural hypotension, patients lying down to measure blood pressure is normal, stand up to appear dizziness, no energy, blood pressure 90/60mmHg; short-acting drugs to take effect faster, will also appear to lower blood pressure. Therefore, patients whose blood pressure was previously high and now falls to normal should consider the diagnosis of hypertension, whether there are any diseases that cause blood pressure to become normal, whether to take antihypertensive drugs to lower blood pressure to normal, etc.