No one wants it, yet it's the body's way of getting your attention when something is wrong. You're probably sufficiently in tune with your body to know when the pain is just a bother, perhaps the result of moving furniture a day or two before or eating that third enchilada.
Wrist Blood Pressure Monitors use the radial artery to measure blood pressure instead of the more commonly used brachial artery. The key is to place the monitor on your wrist properly, just above the wrist bone and then to hold your wrist up level with or above your heart.
A blood pressure cuff will be placed on your arm to maintain a small amount of pressure during your donation. The cuff is not used to measure blood pressure. Your arm will be thoroughly examined to find a suitable vein before being cleaned with an antiseptic sponge. This kills normal bacteria (germs) on the skin.