If the systolic blood pressure is 90mmHg and diastolic blood pressure is 60mmHg, it is possible that it is caused by congenital hereditary reasons, that is, the patient is born with low blood pressure, but such patients often do not have any uncomfortable situation. In addition, it is also possible that the patient overdoses on antihypertensive drugs, resulting in secondary low blood pressure. In addition to this, there are some people with severe heart failure who have low blood pressure in the advanced stages of heart failure. There are also some people who are basically unable to eat in the advanced stage of tumor and need to rely on intravenous fluids to maintain nutrition, and patients are also prone to hypotension. Some people may have acute right ventricular myocardial infarction, also prone to the phenomenon of hypotension, in addition to some people may be unexplained low blood pressure or severe anemia, if you want to further clarify the diagnosis, it is recommended that you can first check the liver function, renal function, serum ions, and blood routine laboratory tests.