Many patients ask, “Doctor, which hand should I measure my blood pressure on?” There are normal differences in blood pressure measurements, and the left upper arm may not be the same as the right upper arm. So when measuring blood pressure, which arm should I choose, the left arm or the right arm? There are different views on this: 1. The “left-handed” school believes that the left arm is closer to the heart, and the closer to the heart the more accurate the measurement, so the left arm should be measured; 2. The “right-handed” school believes that, in general, the right side of the blood pressure tends to be slightly higher than the left side, so it should be measured on the right arm. The “right-handed” school believes that, in general, blood pressure on the right side tends to be slightly higher than on the left side, so the right arm should be measured. Let’s take a look at the recommendations of the Chinese Guidelines for Blood Pressure Measurement: In normal people, the blood pressure of the right upper extremity is generally higher than that of the left upper extremity, and the difference between the two is 5-10 mmHg, which is determined by the anatomy and physiology of the blood vessels. This is because the right brachial artery comes from the branches of the cephalic trunk and the left brachial artery comes from the left subclavian artery. Both the cephalic trunk and the left subclavian artery come from the aorta, and the cephalic trunk is a larger branch of the aorta, and the left subclavian artery has a smaller branch, so the right side of the blood pressure is naturally higher. Therefore, right-handed blood pressure is now common in clinical practice. However, there are many people with higher blood pressure in the left upper arm. Many studies have found that there is a difference in blood pressure between the right and left upper arms, and this difference is not related to the use of the left hand or the right hand. The interarm difference in blood pressure between hypertensive patients was ≥5 mm Hg in 31% of cases, and the proportion of cases in which one side of the blood pressure was higher than the opposite side of the right and left upper arms was comparable (i.e., the proportion of cases in which the left upper arm had a higher blood pressure than the right upper arm was approximately 50%, compared with the proportion of cases in which the right upper arm had a higher blood pressure than the left upper arm). Therefore, the guidelines recommend that left and right upper arm blood pressures be measured at the first examination. When the blood pressure in the right and left upper arms are not the same, the blood pressure measured in the arm with the higher value is used. Therefore, people who have their blood pressure taken for the first time may choose to have both their left and right upper arm blood pressure measured to determine which arm has the higher blood pressure. Use the side with the higher blood pressure as the upper arm for blood pressure measurement. Generally, after a person forms a difference between the blood pressure of the left and right arm, the direction will not change within a period of time, so the next time we measure the blood pressure of the high arm as the standard. For example, if we take the left hand as the standard, then we will measure the left hand every time. However, the difference may change over a longer period of time. Therefore, regular measurements should be taken to see if there is any change in the direction of the difference between the left and right hand blood pressure. To summarize, blood pressure should be measured using the blood pressure value of the arm with the higher value.