Some wrist sphygmomanometers may be accurate if used strictly according to instructions. However, the American Heart Association recommends using a home sphygmomanometer to measure blood pressure in the upper arm rather than the wrist or finger.
Wrist sphygmomanometers are extremely sensitive to position. To get an accurate reading of blood pressure when using a wrist monitor, your arm and wrist must be flush with your heart. Even so, blood pressure measured at the wrist is usually higher and less accurate than that measured at the upper arm. That's because the arteries in the wrist are narrowed and don't penetrate your skin as deeply as the upper arm.
Some people can't get their blood pressure measured in their upper arms because they have large arms, or they find it painful to get their blood pressure measured. In these cases, measuring blood pressure at the wrist is acceptable.
It is common to get different blood pressure readings at home using any type of monitor than in the doctor's office. If you have a wrist sphygmomanometer, it's best to take you to a doctor. Your doctor can then check the accuracy of your wrist blood pressure monitor by checking your blood pressure using a standard upper arm monitor and wrist monitor in the correct position of the same arm. Also make sure to use proven equipment.