Previously high and now low blood pressure may be caused by overdose of antihypertensive drugs, sudden myocardial infarction and hypertensive heart disease. 1. Overdose of antihypertensive drugs: If patients take too much antihypertensive drugs, it may also lead to the phenomenon of high blood pressure in the past and now low. 2. Sudden myocardial infarction: Sudden myocardial infarction leads to part of myocardial necrosis, which makes myocardial contraction drop significantly, leading to a decrease in cardiac output, which results in the phenomenon of previously high blood pressure and now low blood pressure. 3. Hypertensive heart disease: long-term high blood pressure causes hypertensive heart disease, leading to the occurrence of severe heart failure, resulting in a significant decline in cardiac output, there may be previously high blood pressure is now low. When the patient has high blood pressure before and now low, it is recommended to go to the hospital to find out the cause of the disease and carry out standardized treatment according to the cause of the disease.