ELI5: Why do I get dizzy when I stand up?

Imagine you're a water balloon lying down. All the water (that's your blood) is spread out evenly.

When you suddenly stand up, gravity pulls the water down towards your feet. This means less water (blood) goes up to your brain really quickly.

Your brain needs blood to work properly! It's like a car needing gas. When it doesn't get enough, it gets a little confused for a second. That confusion is what makes you feel dizzy.

Think of it like this:

• You're lying down: Blood is spread out.
• You stand up fast: Blood rushes to your legs.
• Less blood reaches your brain: Brain goes "Whoa, where's the gas?!"
• You feel dizzy for a moment: Brain catches up.

• Your heart starts beating faster to pump more blood.
• Your blood vessels squeeze tighter to push the blood upwards.

Sometimes, if you're dehydrated (not enough water in your body), or haven't eaten in a while, you have less blood volume overall. This makes the dizziness worse. So, drink plenty of water and eat regularly!

If you always feel dizzy when you stand up, you should tell a grown-up so they can ask a doctor.