Most often, a small difference in blood pressure readings between arms isn't a concern. But a difference of more than 10 millimeters of mercury (mm Hg) might cause worry. The difference can be in the top number, known as systolic pressure. Or it can be in the bottom number, known as diastolic pressure.

People who have a blood pressure difference between arms of 10 to 15 mm Hg for systolic pressure over and over are more likely to have vascular disease. They also have a greater risk of getting heart disease over time.

A difference of more than 10 mm Hg in blood pressure measurement between the arms over and over can be a sign of a health condition such as:

• Blocked blood vessels in the arms, known as peripheral artery disease.
• Atypical connections between blood vessels in the arms, known as fistulas.
• Persistent opening between two major blood vessels leading from the heart, known as patent ductus arteriosus.

If you have a large difference in blood pressure readings between arms, talk to your healthcare professional. Your healthcare professional might use the arm with the higher reading to measure your blood pressure in the future.