HI, thanks for using healthcare magic It is possible that the blood pressure reading itself is ok but that there is a decrease in your standing blood pressure when compared to you sitting or lying BP. This drop in blood pressure on standing is called orthostatic hypotension. You may want to determine if this is the case by visiting your doctor for assessment. There are different possible causes such as dehydration, side effect of medication, heart disease, may also be related to parkinsons. There is general treatment then treatment directed towards any specific cause found. General treatment involves ensuring good fluid intake, standing slowly I hope this helps