If the difference between the right and left arms is within 20mmHg, refer to the side with the higher blood pressure; if the difference is greater than 20mmHg, consider whether the subclavian artery is narrowed on the lower side. 1. Difference within the range of 20mmHg: The error of 20mmHg may be due to factors such as emotion, heart leveling of the arms, etc. During measurement, you can take several measurements and try to control the variables of measurement. 2. Difference greater than 20mmHg: the difference between the blood pressure of the left and right arms is too large and exclude the measurement factors, we should consider whether it is due to vascular lesions, a common vascular lesion is the stenosis of the subclavian artery leading to insufficient blood supply, in the measurement of the affected side of the blood pressure will be low signs. Left and right arm blood pressure is not the same, to timely hospital consultation, seek professional physician’s guidance, so as not to miss the diagnosis of delayed condition.