The result of blood pressure dropping to 54/20 millimeters of mercury depends on the previous blood pressure level and why the reading dropped, reports the American Heart Association. Nothing may happen, or a person's health may be at risk. No specific reading designates dangerously low blood pressure, and doctors assess risk according to noticeable symptoms.
A low blood pressure level or a single drop in blood pressure without symptoms does not require treatment, explains the American Heart Association. As long as blood pressure readings are under 120/80, doctors usually consider them healthy. However, an abrupt drop of 20 millimeters of mercury or more may cause fainting or dizziness. Other symptoms of dangerously low blood pressure include blurred vision, inability to concentrate, fatigue, nausea and depression. Patients may also manifest rapid shallow breathing and clammy skin.
Athletes, nonsmokers, pregnant women and those taking certain medications may be healthy and have low blood pressure, according to Mayo Clinic. Low blood pressure due to dehydration triggers a range of symptoms such as dizziness, fatigue, vomiting, fever and diarrhea. Heart problems, endocrine problems, infections, allergic reactions and blood loss from major injuries all may cause severe life-threatening drops in blood pressure with accompanying symptoms. Treatment for low blood pressure in these situations addresses the underlying health problem.