Blood pressure question

[Campaigner8]

When I woke up this morning, my blood pressure was 132/94. I laid back down and took my blood pressure and it was 115/78. Why would this be so?

[Ger57]

There are different laws of physics and control systems at work to keep the blood pressure throughout your body at a more or less of equal value.

Of course gravity plays a role, but also the action of the tiny muscles of the arteries and the muscles that surround the veins influence blood pressure in the body.
Further the hearts action and the size of the arteries/veins plays a role.
In a healthy person this is a well balanced system that keeps the blood pressure fairly constant, even when i.e. suddenly standing up from a sitting position.

Still some variations will occur. Therefore, if one wants to compare blood pressure measurements taken at different moments, it is of importance to do the measurements always in the same posture.