Why right wrist give higher reading than left wrist in a bp monitor? left 123/81 and it's always ok right 140/99 it's the first time i try the right that's a huge difference. which one do i believe?

First, I do not trust wrist manometer but you can use it just to monitor when you have a standard blood pressure checked in upper arm. Remember, you have to put the wrist at the exact level (heart level) when you check BP at right and left wrist. If the wrist is lower either the right or left, the result will be higher. Furthermore, BP is usually 5-10 mg Hg higher on the right side in most people.