To your health: The highs and lows of blood pressure

By Ali Hamzei, MD, Scripps Health

It’s routine at nearly every doctor’s appointment—the nurse wraps a blood pressure cuff around your arm, pumps it up a bit, and waits for the reading. Between appointments, you may also have taken your own blood pressure using the do-it-yourself machine at the drugstore.

What exactly do those numbers mean? Blood pressure measures the force of blood against the walls of the blood vessels. It is measured in millimeters of mercury (mmHg), and is expressed in two numbers, such as 120/80mmHg. The first number (systolic) measures the pressure as the heart beats. The second number (diastolic) represents the pressure between heartbeats as the blood flows to the rest of the body.

According to the current national guidelines, a normal blood pressure reading is less than 120 systolic and less than 80 diastolic. High blood pressure, also known as hypertension, is defined as 140/90 mmHg or above. Even if it is not in the “high” range, a reading of 120 to 139 systolic and 80 to 89 diastolic indicates prehypertension, which increases the risk of developing high blood pressure.

In the U.S., about 1 in 3 adults will have blood pressure reading that is too high, indicating a possible risk of serious cardiovascular problems including heart attack, stroke and kidney disease. The higher the pressure, the greater the risk of heart disease and stroke. In fact, beginning at 115/75, with each 20 mmHg increase in systolic blood pressure and 10 mmHg diastolic, the risk of stroke and heart attack doubles. After age 50, a systolic blood pressure above 140 mmHg is a greater risk factor for stroke and heart disease than diastolic blood pressure.

Although some people with high blood pressure experience such symptoms as headache, shortness of breath, and blurred vision, most patients experience no symptoms. Therefore, without testing you won’t know if your blood pressure increases—or even if it is high to begin with. That’s why it’s important to have a blood pressure check at least once a year, either by a professional or with a self-testing machine.

Age is one of the most significant risk factors for high blood pressure. Lifestyle also plays a role; behaviors that can help keep blood pressure under control include maintaining a healthy weight, exercising regularly, not smoking and limiting the amount of sodium in your diet. Unfortunately, fewer than half of adults with high blood pressure take steps to keep it under control. If lifestyle modifications are not successful, medication may be needed. This may be the case for people who have a genetic tendency toward high blood pressure.

While it doesn’t get nearly as much attention, low blood pressure can also be a problem.

When blood pressure is much lower than normal, the heart, brain, organs and tissues do not get enough blood. As a result, they are deprived of the oxygen and other nutrients they need to function optimally. Symptoms of hypotension may include fatigue, lack of energy, lightheadedness, confusion, blurry vision, fainting and nausea or vomiting.

Low blood pressure can have several causes. In severe cases, it can be triggered by a sudden loss of blood, a serious infection, or a heart attack. Some people experience low blood pressure when they stand suddenly after sitting or lying down for a while; in these cases, the drop in blood pressure usually lasts only a few minutes.

Alcohol, dehydration, and changes in heart rhythms all can lead to low blood pressure. In addition, some medications for anxiety and depression, diuretics, and painkillers may also keep blood pressure lower than normal.

Most people with low blood pressure do not require treatment unless it causes symptoms that disrupt their everyday lives. If treatment is needed, your physician will determine the best approach based on the cause of your hypotension and your symptoms.

Ali Hamezi, MD, is a cardiologist with Scripps Health. “To Your Health” is brought to you by the physicians and staff of Scripps. For more information or for a physician referral, please call 1-800-SCRIPPS or visit