Blood pressure is the strength of blood which is approaching against the arteries walls. Every time our heart beats, it pumps out blood into the arteries. Pressure of blood or blood pressure is maximum when heart, pumping the blood. This pressure is known as systolic pressure. When heart is at relaxed means time between two beats, in that period blood pressure falls. This pressure is known as diastolic pressure. Blood pressure is measured using these two conditions. Usually they're written one above or before the other. Normal systolic pressure is 120/80 and diastolic pressure is 90/60. If blood pressure reading is below 90/60 then you have low blood pressure problem.
Low blood pressure is medically known as hypotension. If symptoms of low blood pressure are mild, then it usually needs no treatment. But if it is constantly low, then it can cause severe heart problems, fainting and also cause neurological and endocrine diseases. In very severe condition, hypotension can also cause lack of oxygen and nutrients in body and in that situation body can go into shock or it can also develop a life-threatening condition.
Some people have low blood pressure constantly, but they have no signs and their low blood pressure readings are usual for them. In other cases, blood pressure drops below normal due to some happening or medical circumstance. Some people may feel symptoms of low pressure when stand up too speedily. Low blood pressure is dangerous only if it causes fainting, giddiness or in some severe cases, shock.