Some 47 million Americans run or jog, many doing so because running reduces health risks and early death. But the American Heart Association (AHA) estimates more than double that many Americans live with high blood pressure, making it likely that many are running with high blood pressure, too.

It's possible to have high blood pressure even if you exercise, just as it's possible to exercise safely with high blood pressure. A May 2019 study in the journal Heart even found that up to a third of high school, college and professional athletes had hypertension, the medical term for high blood pressure, based on U.S. guidelines updated in 2017 by the American College of Cardiology (ACC) and AHA.

Physical activity can help lower blood pressure over time, but safely running with high blood pressure requires taking a few extra steps. It starts with knowing your blood pressure, because "hypertension is a 'silent disease' that is often without symptoms," says Donna K. Arnett, PhD, MSPH, dean of the University of Kentucky College of Public Health and former AHA president.

With every pump of your heart, your blood exerts pressure on blood vessels. "Think of a garden hose," suggests William O. Roberts, MD, MS, director of the Family Medicine Sports Medicine Program at the University of Minnesota Medical School in Minneapolis. "If someone coordinated turning the hose on and off, while another person opened and closed the end valve, you would mimic the heart and blood pressure."

Two forces create that pressure, and your blood pressure reading includes the systolic pressure, which occurs as blood leaves the heart and enters arteries, and the diastolic pressure, which occurs as the heart rests between beats. Elevated or high blood pressure means one or both of those forces are too high, straining your circulatory system, according to the ACC.

Doctors assess blood pressure at most wellness visits, but self-checks with free in-store or at-home monitors helps, too. You need to stay seated and still to get the most accurate measurements though some fitness apps and monitors also perform checks during workouts. Take measurements at rest, but also before and after exercise, to see how your readings change. According to the AHA,, exercise tends to lower blood pressure over time, but systolic pressure may increase during the actual workout because your heart pumps faster. The change is generally temporary. Increased blood flow to active muscles triggers changes that tell blood vessels to widen. This helps normalize pressure. For people cleared for physical activity, experts at UC Davis Health suggest it's OK if systolic pressure rises during exercise, though numbers should eventually normalize. During cardio workouts, it's possible systolic pressure can even soar to around 200 millimeters of mercury. (For reference, a healthy systolic number is below 120 millimeters of mercury.) Be mindful of weight lifting, too, as it sometimes leads to brief but significant blood pressure spikes, according to Mayo Clinic.

Exercise, though good for you, doesn't confer high blood pressure immunity. A review of more than 50 studies, published in the British Journal of Sports Medicine in January 2015, found little difference in the prevalence of high blood pressure between athletes and non-athletes. Other studies, including one from February 2017 in Biomedical Research International, suggest that extreme exercise like marathon running may raise blood pressure overall and that it's linked to serious heart events, like heart attacks.

"Patients experiencing significant blood pressure increases during exercise may have a severe headache or difficulty concentrating," says Dr. Arnett. "They might also have trouble with their vision or a 'pounding' in their chest." If you experience these symptoms — or fatigue, dizziness, difficulty breathing, flush (red) face or a flutter in your heart — seek medical attention immediately.

If you're diagnosed with high blood pressure or concerned about risks from running, talk to your doctor. Avid runners may need to adjust runs, alternate with lower-intensity exercise like yoga or change their diet. And, if you want to start running after a blood pressure diagnosis, work with your doctor or a fitness trainer to develop an individualized plan for exercising safely.