Hi Diah,   It is not unusual for your blood pressure to be different in one arm than the other. Blood pressure may be slightly higher in your dominant arm. For example, if you are right-handed, you may get a higher blood pressure reading when taken on your right arm. Usually the difference between arms is 10 mm Hg or less. Now, if you have heart disease, studies show the difference between arms to be greater. The arm with the higher blood pressure, is the one you should monitor.  If you are a stroke or heart disease candidate it is a good idea to periodically monitor the blood pressure in both arms.   All the best, Lisa Nelson RD 7 Natural Ways to Lower Blood Pressure