Low blood pressure in the left hand and high blood pressure in the right hand can be due to normal physiologic causes, but can also be caused by diseases such as aortitis, congenital arteriovenous malformations, and subclavian artery steal syndrome. Blood pressure refers to the lateral pressure acting on the wall of the blood vessel per unit area when the blood flows in the blood vessel, which is related to the output per beat, peripheral resistance, heart rate, elasticity of the wall of the aorta and the aorta, the volume of circulating blood and the volume of blood vessel, which results in the following reasons for the low blood pressure in the left hand and high blood pressure in the right hand: 1. Physiological reasons: the main performance of the right side of the blood pressure is higher than the left side, the difference between the two sides of the blood pressure is generally not more than 10-20mmHg, because the left side of the heart is closer to the vascular circulation of the resistance is smaller, the usual situation to the right arm of the blood pressure shall prevail. 2. Aortitis: Aortitis is a chronic non-specific inflammatory disease of the aorta and its main branches and pulmonary artery, which can cause arterial stenosis and occlusion in different parts of the arteries, resulting in a greater resistance to circulation of the brachial artery in the right arm and a higher blood pressure. 3. Congenital arteriovenous malformation: it can be manifested as the narrowing of the brachial artery of the right arm, and the blood pressure of the right arm is greater. 4. Subclavian artery steal syndrome: This can lead to ischemia in the left arm and smaller blood pressure, resulting in a higher blood pressure in the right arm than in the left arm. Low blood pressure in the left arm and high blood pressure in the right arm may also be other reasons, should be timely hospital consultation, standardized treatment under the guidance of the doctor.