The heart keeps approximately 5 liters of blood pumping throughout the body, according to the Franklin Institute. Doctors can determine the health of the heart and blood vessels by measuring the blood pressure---the force the blood exerts on the walls of the blood vessels. A blood pressure reading consists of two figures; the systolic pressure, which indicates the force of the blood as the heart contracts, and the diastolic pressure, which indicates the force of the blood as the heart relaxes. The two readings of blood pressure can fluctuate due to factors ranging from everyday stress to serious health conditions.
Normal Blood Pressure
Doctors consider the normal blood pressure level for a healthy adult to read less than 120 mmHg for the systolic pressure and less than 80 mmHg for the diastolic pressure, according to the American Heart Association. Because blood pressure can fluctuate from minute to minute, doctors recommend charting blood pressure results over time to get an accurate assessment of them.
High Blood Pressure
To receive a diagnosis of high blood pressure, a condition known as hypertension, the patient must consistently demonstrate blood pressure readings of more than 140 mmHg systolic pressure and/or 90 mmHg diastolic pressure, as described by the American Heart Association. Those patients with systolic pressure readings between 120 mmHg and 139 mmHg or diastolic readings between 80 mmHg and 90 mmHg suffer from prehypertension---a condition that warns of the onset of high blood pressure. Controlling blood pressure fluctuations in those with prehypertension and making lifestyle changes to lower pressure can help prevent high blood pressure.
Low Blood Pressure
Because one in three adults in the United States suffers from high blood pressure, according to the National Heart Lung and Blood Institute, most strive to get blood pressure lower. But too low, a condition known as hypotension, can become dangerous because vital organs may not receive enough oxygen and nutrients. Doctors consider a systolic pressure of less than 90 mmHg or the diastolic pressure of less than 60 mmHg as low blood pressure, as described by MayoClinic.com. Blood pressure that fluctuates into the low range is only considered a problem when worrisome symptoms appear.
Blood pressure can fluctuate from high to low in short periods of time. Each beat of the heart can produce varying pressures. The position of the body, breathing rhythm, stress level, physical condition, medications, foods, drinks and even time of day contribute to blood pressure fluctuations. Medical conditions such as pregnancy, heart problems, dehydration, infections and allergic reactions can also cause fluctuations in blood pressure. If the pressure fluctuates dramatically, such as falling more than 20 pressure points, symptoms can occur.
When blood pressure fluctuates down to a lower pressure, the patient may experience dizziness or fainting due the brain failing to receive enough blood. Other symptoms of low blood pressure include blurred vision, nausea, shallow breathing and thirst. As blood pressure fluctuates higher patients may experience headaches, but high blood pressure often fails to produce any noticeable symptoms until damage to the blood vessels result in serious conditions such as a heart attack or stroke.