Think of it, if the water pressure in your house is too low, you can't take a shower. The water will simply trickle out because there is not enough pressure behind it to spout out. Low blood pressure is the same. You are not pumping enough blood through your system to provide adequate circulation. This leads to fatigue and weakness.
A good tip that will illicit the presence of low blood pressure is that of dizziness or lightheartedness when standing up or changing position abruptly. This symptom can be formally diagnosed with atilt-table testing procedure. Most of the time, though, your doctor can attest to this by continued readings of low blood pressure when entering his office.
This deficiency can be counter changed by prescription drugs that can raise blood pressure. Some of these medications include Florinef and midodrine. Usually these prescriptions will raise blood pressure only 10 points or so. Most of the time medications are only needed for a few months. It simply helps the body to remember how to make the substance it needs properly. Please see your physician for further commentary on this.