You take blood pressure in the left arm because it's often the default for heart-related readings, but the crucial thing is to check both arms at the first visit to find the higher reading, as a significant difference (over 10 mmHg) can signal underlying issues like narrowed arteries, increasing cardiovascular risk, so that higher arm is used for future checks. A consistent difference indicates a potential problem, even in healthy people, making both-arm checks vital for accurate risk assessment.
It's a good idea to have your blood pressure measured in both arms at least once, since the reading in one arm (usually the right) may be slightly higher than that in the left. In general, the arm-to-arm difference in systolic blood pressure is 5 points or less.
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.
In general you should take your blood pressure on your left arm. If you are unable to take your blood pressure on your left arm, you may take it on your right arm instead but you should be aware that there may be differences between your right and left arms.
Physician- or health professional-related
One common error in the clinical setting is failure to include a five-minute rest period. Errors can also include talking during the measurement procedure, using an incorrect cuff size and failure to take multiple measurements.
Blood pressure has a daily pattern. Usually, blood pressure starts to rise a few hours before a person wakes up. It continues to rise during the day, peaking in midday. Blood pressure typically drops in the late afternoon and evening.
Normal systolic blood pressure should be around 120. The UK study identifies 10 points as the critical threshold of difference between the arms. That's lower than the previous guideline of 15. For example, systolic blood pressure of 118 in one arm and 120 in the other causes little concern.
They found using a cuff that was too small mistakenly resulted in higher blood pressure readings in 39% of participants, while using a cuff that was too large missed 22% of those who did have hypertension.
Factors that could cause a high first blood pressure reading
For optimal results, the American Heart Association (AHA) recommends sitting down and relaxing for at least five minutes before a blood pressure reading. Your first blood pressure reading may be higher than normal without this relaxation time.
Higher pressures are more frequent in the right arm and range in most individuals from 10 to 20 mmHg or greater in systole, and to a similar extent but less often in diastole. A BP difference between the left and right arms—even when large—is statistically a normal variant and need not necessarily cause concern.
Your healthcare professional might recommend taking your blood pressure at the same times each day. Don't measure your blood pressure right after you wake up. You can prepare for the day, but don't eat breakfast or take medicine before measuring your blood pressure.
Systolic blood pressure is the best way to predict future cardiovascular events and death, irrespective of age, according to new research. But in younger people, diastolic blood pressure could still be important.
Before you get your blood pressure checked, sit down, quiet your mind, and breathe deeply for a few minutes. Come prepared. Come with a list of questions to address and a mental plan for the appointment. The more in control you feel during visits, the better equipped you'll be to control your breathing and remain calm.
Ignore the first day's readings altogether, because they might not be accurate as you're not familiar with your monitor yet. At the end of the week you will have a useful picture of what your blood pressure is normally like.
The "80/40 rule" for blood pressure cuffs means the inflatable bladder should wrap around 80% of your upper arm's circumference (length) and be wide enough to cover about 40% of the arm's width, ensuring accurate readings by properly occluding the brachial artery. Using a cuff that's too small gives falsely high readings, while one that's too large gives falsely low readings, making correct sizing crucial, especially for individuals with larger arms.
Factors That Can Exaggerate Blood Pressure Readings
Anxiety doesn't cause long-term high blood pressure. But bouts of anxiety can trigger temporary rises in blood pressure. Temporary rises in blood pressure that happen often, such as every day, can damage the blood vessels, heart and kidneys. This is the same type of damage seen in people with long-term hypertension.
The left common carotid and left subclavian arteries to come directly off the aorta. These differences mean that the risk for increased turbulence leading to arterial thrombosis is not the same for the right and left subclavian arteries.
"Stroke level" blood pressure is a hypertensive crisis, defined as a reading of 180/120 mmHg or higher, which is a medical emergency requiring immediate help (call 911 or emergency services) as it significantly increases the risk of a stroke, heart attack, or other life-threatening conditions, especially if accompanied by symptoms like severe headache, shortness of breath, or vision changes.
Wrist and finger monitors are not recommended. They give less reliable readings. Choose a monitor that has been validated. If you are unsure, ask your health care professional or pharmacist for advice or find options at validatebp.org(link opens in new window).
Can Hydration Help Lower Blood Pressure? Staying well hydrated can help prevent temporary spikes in blood pressure. However, drinking water is not a treatment for high blood pressure. In fact, drinking too much water can sometimes raise your blood pressure.
A blood pressure of 140/90 mmHg is Stage 2 hypertension, which needs medical attention and lifestyle changes, but usually not an immediate hospital trip unless you have severe symptoms like chest pain, shortness of breath, vision changes, or signs of stroke, in which case you should call for emergency help (like 911/000) immediately. For a single reading, it's best to recheck after relaxing and then contact your doctor for advice and follow-up, as persistent readings above 140/90 warrant a check-up to prevent long-term damage.
How does caffeine affect blood pressure? Caffeine may cause a brief rise in your blood pressure, even if you don't have high blood pressure. This short-term spike in blood pressure happens mainly in people who don't drink caffeine often, rather than in those who do.
Even higher blood pressure (with the systolic blood pressure 180 or higher, the diastolic blood pressure more than 120, or both) is called a hypertensive urgency if there are no related symptoms. Or it's called a hypertensive emergency if there are symptoms indicating damage to the brain, heart, or kidneys.