When measuring blood pressure, even small errors lead to incorrect values, which in turn contributes to incorrect dosage of medication. And this is not a joke.
No need to measure the pressure immediately after eating. When we eat a large amount of blood sent to the digestive organs, so the value may be lower than it really is. After the meal should take at least hours.
You are measuring on the wrong hand. Typically, the pressure in one arm lower than the other. Early treatment of hypertension need to measure it on both hands, and in the future to always choose the arm where blood pressure was higher.
The hand squeezed clothes. If you move the sleeve is tight enough, it can compress the arm, as a result, we will get incorrect values. A thin shirt should not be removed, the cuff is worn on top.
You are wrong to hold your arm and the cuff. If the cuff is above heart level, the values may be too low. Therefore, the cuff should be at heart level, only then the value will match the actual.
Have you used alcohol, strong tea or coffee. All this leads to incorrect measurement results. So, alcohol can expand blood vessels, which lowers blood pressure. However, after that the pressure again rises and becomes higher than it was before. And after tea or coffee pressure may increase within a few hours.