Most doctors consider blood pressure too low only if it causes symptoms. Some experts define low blood pressure as readings lower than 90 mm Hg systolic or 60 mm Hg diastolic. If either number is below that, your pressure is lower than normal. A sudden fall in blood pressure can be dangerous. A blood pressure reading appears as two numbers. The first and higher of the two is a measure of systolic pressure, or the pressure in the arteries when the heart beats and fills them with blood. Related symptoms are Dizziness or lightheadedness; Fainting; Blurred or fading vision; Nausea; Fatigue; Lack of concentration, shock. Low blood pressure is a reading of less than 90/60mmHg. Treatmnets to be used ,Use more salt. Experts usually recommend limiting salt in your diet because sodium can raise blood pressure, sometimes dramatically.Drink more water. Fluids increase blood volume and help prevent dehydration, both of which are important in treating hypotension,Wear compression stockings,Medications. The cause of low blood pressure can be determined with blood tests, radiologic studies, and cardiac testing to look for heart failure and arrhythmias.