
Why Does Everything Go Black When You Stand Up Too Fast?
Almost everyone has experienced it. You stand up from the couch, your vision suddenly fades, everything turns gray or black for a few seconds, and sometimes you even feel dizzy. It feels strange, but there's actually a simple explanation.
When you stand up quickly, gravity pulls blood toward your legs. For a brief moment, less blood reaches your brain. Since your brain depends on a constant supply of oxygen, even a short drop in blood flow can make your vision fade or cause dizziness. Your body reacts almost instantly by making your heart beat faster and tightening your blood vessels to restore normal blood pressure. In most healthy people, the whole process only takes a few seconds.
This is called orthostatic hypotension. It can happen more often if you're dehydrated, haven't eaten for a long time, are very tired, have been lying down for a while, or take certain medications.
Most of the time it's harmless. But if it happens frequently, causes you to faint, or starts occurring for no obvious reason, it's worth getting checked by a healthcare professional.
Your eyes aren't failing.
Your brain is simply waiting for the blood to catch up.