A large difference in blood pressure between the left and right arms needs to be considered as a possible cause of arterial stenosis or occlusion in the left and right arms due to atherosclerosis, arteritis, or arterial entrapment. Under normal circumstances, there is a physiologic difference in blood pressure between the right and left arms of the human body, mainly due to the difference in the origin of the brachial artery in the right and left arms. The brachial artery in the right arm originates from the cephalic trunk, a larger branch of the aorta, while the left brachial artery in the left arm originates from the subclavian artery, a relatively small branch of the aorta. In the right and left arms, because of the differences in the arteries from which they originate, there is a difference in pressure within the right and left brachial arteries. Normally, blood pressure in the right arm should be slightly higher than that in the left arm, with a difference of 5-10 mmHg between the two. However, if the difference between the right and left arms is large, it is usually triggered by the narrowing or occlusion of blood vessels caused by atherosclerosis and arteritis. For example, the common narrowing of the carotid and supraclavicular arteries will result in a lower blood pressure in the left arm and a higher one in the right, resulting in a difference of more than 20 mmHg. If there is a large difference between the blood pressure of the left and right arms, it is necessary to consult a doctor in a timely manner, and follow the doctor’s instructions for examination, such as ultrasound examination of the subclavian artery, to clarify whether there is a subclavian artery or the carotid artery issued by the site of the emergence of serious atherosclerotic stenosis or arteritis stenosis, or even occlusion. After identifying the cause of the disease, we should follow the doctor’s advice and timely treatment, do not take medication without authorization, and do not leave it unattended, which will lead to a delay in the condition of the disease.