What can cause dizziness when getting out of bed?
Postural hypotension is a sudden, transient drop in blood pressure that happens when rising from sitting or lying down, and it causes dizziness. Folks who take high blood pressure medication often experience postural hypotension as a side effect. It occurs because some high blood pressure medications block the autonomic nervous system (ANS) to keep blood pressure down. So, the baroreceptors in the ANS, which respond quickly to changes in the body's position, take longer to respond. It is a drug side effect that we often advise people about.
To prevent or reduce the dizziness caused by postural hypotension, I've found it is best to get up more slowly or to sit at the side of the bed for a moment to give the ANS time to "catch up" with your position change before you stand and blood is shunted to the lower body.