The blood pressure in the left arm is not higher than that in the right arm; on the contrary, in general, the blood pressure in the right arm is higher than that in the left arm by an average of 5 to 10 mmHg. This is related to the vascular structure of the right and left arms. The brachial artery of the right arm comes from a larger branch, the first branch of the aortic arch, the head-arm trunk, while the brachial artery of the left arm comes from a smaller branch, the third largest branch of the aortic arch, the left subclavian artery, so that the blood pressure of the right arm is higher than that of the left arm. There are also a few people whose blood pressure in the left arm is higher than that in the right arm, which is due to structural variations of the heart and blood vessels, such as right-sided heart and right-sided brachial artery stenosis. When the difference between the blood pressure of the right arm and the left arm is more than 20mmHg, it is necessary to be alert to aortic coarctation and peripheral vascular disease, and it is necessary to go to the hospital in time to clarify the cause of the disease and follow the doctor’s instructions for treatment.