Why you may feel dizzy or faint when standing up is because not enough oxygen is getting to your brain. In order for you to maintain consciousness your brain must receive a steady supply of oxygen. And how oxygen gets there is via your blood.
Under normal healthy conditions, your body can respond very quickly to a change in position. When you stand up, there’s a reflex mechanism that keeps the blood flowing to your brain so it does not pool in your lower extremities. Essentially, two blood related changes occur simultaneously: your heart increases its output and your blood vessels constrict.
Now if these do not occur fast enough, then your blood pressure drops and your brain gets that dizzying, faint feeling. Blood pressure that drops when standing up is called postural hypotension. It’s common to experience this standing up dizziness or faint feeling occasionally.
However, if the mechanisms that maintain a high enough blood pressure to keep you from feeling dizzy or faint are not working properly, then you have a health condition known as orthostatic hypotension. And it’s a common health condition and concern in the elderly because of the risk of falling.
Standing up hypotension is frequently associated with:
- heat exposure
- long term bed rest
- long periods of sitting with legs crossed
- heart problems ~ bradycardia, heart attack, heart failure
- nervous system disorders ~ Parkinson’s disease, multiple system atrophy, amyloidosis
- drug side effect ~ high blood pressure medication, diuretics, beta blockers, tricyclic antidepressants, prescription pain relievers, alcohol
So take it slow whenever you change positions to keep from getting dizzy or feeling faint, especially when going from lying down to standing up.