A blood pressure of 40mmHg is abnormal. If it is 40mmHg systolic, you will die at any time; if it is 40mmHg diastolic, you will also have symptoms of cardiac, cerebral and renal underperfusion, such as pain in the precordial region, dizziness, lightheadedness, weakness, and even dysfunction of the lateral limbs, syncope, and oliguria. The normal range of blood pressure in normal people is 90-140mmHg systolic and 60-90mmHg diastolic. Systolic blood pressure below 90mmHg, or diastolic blood pressure below 60mmHg, is hypotension. If the usual low pressure is around 40mmHg and there are no clinical symptoms, it is recommended to take oral raw pulse drink and increase the salt intake to raise the basal blood pressure. If low pressure of 40mmHg occurs suddenly with symptoms of hypotension, blood pressure should be corrected promptly, apply blood pressure raising drugs such as dopamine and dobutamine at the hospital, and actively find the cause of lower blood pressure and treat the cause.