What Are the Causes of Unstable Blood Pressure?

In as many as 95 percent of reported high blood pressure cases in the United States, the underlying cause cannot be determined, but heredity, age, race, gender, diet and lifestyle are contributing risk factors, according to WebMD. Low blood pressure can be caused by dehydration, trauma and health problems.

Blood pressure is the measure of the force of blood pushing against blood vessel walls. High blood pressure, or hypertension, forces the heart to pump blood harder leading to atherosclerosis and heart failure, states WebMD. Factors that contribute to high blood pressure are smoking, obesity, lack of exercise, too much salt and alcohol, stress, old age, genetics and other diseases. Hypertension is more common in men than women and in blacks than whites. After age 65, black women have the highest incidence of high blood pressure.

Low blood pressure, or hypotension, occurs if a person stands up too quickly after being seated or lying down or after standing too long. Medications can cause low blood pressure, as can other health problems like internal bleeding, severe infection, thyroid disease and heart problems, explains WebMD. Trauma such as severe bleeding and burns can also cause hypotension. For some healthy adults like athletes and regular exercisers, low blood pressure may be normal.