Blood pressure is the force exerted by circulating blood against the walls of the body’s arteries. It is expressed by two numbers: systolic and diastolic pressure. Systolic pressure, the top number, indicates the pressure when your heart beats and pushes blood out. Diastolic pressure, the bottom number, represents the pressure in your arteries when your heart rests between beats. While a single blood pressure reading is often taken, it is common to find different readings between the left and right arms, which can sometimes be a sign of underlying health conditions.
What is a Normal Difference in Blood Pressure?
A minor difference in blood pressure readings between your arms is common and does not indicate a health concern. A systolic blood pressure difference of up to 10 millimeters of mercury (mmHg) between arms is considered within the normal range. These small variations can arise from natural anatomical differences in blood vessel structure or slight fluctuations in blood flow. An occasional small discrepancy is not a reason for worry, but consistent differences warrant attention.
Potential Causes of a Significant Difference
A consistent systolic blood pressure difference exceeding 10-15 mmHg between arms may signal an underlying vascular issue. Peripheral artery disease (PAD), where narrowed arteries reduce blood flow to the limbs, is a common cause. When PAD affects arm arteries, it can result in a noticeable pressure difference. A systolic difference greater than 10 mmHg in the arms is associated with an increased risk for cardiovascular events, including heart attack and stroke.
Subclavian artery stenosis, a narrowing of the artery under the collarbone, can also lead to a significant difference in arm blood pressure. This condition causes the affected arm to have a lower blood pressure reading. Symptoms may include arm pain or cramping with activity, numbness, or dizziness if blood is “stolen” from arteries supplying the brain. Another less common cause is aortic coarctation, a congenital narrowing of the aorta, the body’s main artery. This narrowing results in higher blood pressure in the arms and upper body compared to the legs.
Atherosclerosis, the buildup of plaque in artery walls, is a frequent contributor to these differences. Plaque can accumulate in any artery, including those supplying the arms, leading to reduced blood flow and a pressure disparity. While mild atherosclerosis may have no symptoms, significant plaque buildup can narrow arteries enough to cause blood pressure differences. A consistent systolic difference of 20 mmHg or more indicates underlying vascular disease requiring medical evaluation.
How to Accurately Measure Blood Pressure in Both Arms
To accurately assess blood pressure differences between your arms at home, begin by resting quietly for at least five minutes. Sit comfortably with your back supported, feet flat on the floor, and your arm supported on a flat surface at heart level. Ensure your arm is bare, without clothing underneath the cuff, and use a blood pressure cuff that is the correct size for your upper arm.
First, measure the blood pressure in one arm, following the monitor’s instructions for proper cuff placement about one inch above the elbow. Remain still and avoid talking during the measurement. After the reading, wait one to two minutes before measuring the other arm. Take two or three readings on each arm, separated by a minute or two, and average the last two readings. Recording these measurements, noting which arm was used, will provide valuable information to discuss with a healthcare provider.
When to Consult a Healthcare Provider
If you consistently find a systolic blood pressure difference of more than 10-15 mmHg between your arms on multiple occasions, you should consult a healthcare provider. This persistent difference can be a sign of underlying vascular conditions that may increase your risk for cardiovascular issues. Early detection allows for timely evaluation and management.
You should also seek medical attention if a blood pressure difference is accompanied by other symptoms. These can include arm pain, numbness, weakness, or cramping, especially during activity. Other concerning symptoms include dizziness, fainting, or chest pain, which could suggest more widespread circulatory issues. Discussing these findings with a doctor will help determine the cause and appropriate next steps for your health.