Long-term high blood pressure suddenly low blood pressure, the possible reasons are drug overdose, postural hypotension, blood volume insufficiency and so on. 1. Drug overdose: most of the hypertensive patients need to take long-term antihypertensive drugs for antihypertensive treatment, and some of the patients will adjust the drugs by themselves due to the poor control of blood pressure, and some of the patients may forget to take the drugs because of their poor memory, and there are many times to take the drugs, and then there will be a sudden drop in blood pressure. 2. Postural hypotension: when the body position changes, some hypertensive patients will have a transient drop in blood pressure, which does not need special treatment and can be observed. 3. Insufficient blood volume: some hypertensive patients will take diuretics and so on, which will lead to insufficient blood volume, and a sudden drop in blood pressure can also occur. Long-term hypertension suddenly low blood pressure, must pay attention to, timely medical treatment, clear cause for targeted treatment.