How important is for arm to be supported while measuring bp ? my diastolic value tends to rise when arm is not supported. supported <80 without >85

Critical: It's critically important. When your arm is not supported, you are performing isometric exercise which most assuredly will raise your BP and give you a false reading. Your arm MUST be supported to obtain an accurate reading. Your measurements of

Bp readings: no real difference either way. both reading are good

Both BP cuff &amp; arm: support critical. (a) The artery &amp; cuff over artery must be at heart level (vertically), to minimize gravitational effect on BP. I.e. the goal is central BP at heart/aorta level. Additional keys for accuracy: (b) mercury manometer, (c) proper cuff size, (d) relaxing arm muscles, (e) only single heart beat is sampled for systolic, another for diastolic, (f) well below 120 &amp; 80 best. Errors common.