Why does anxiety causes lightheadedness?

Anxiety may cause a person to feel lightheaded if the person is hyperventilating due to excess stress, notes Calm Clinic. Hyperventilation leads to a deficiency of carbon dioxide in the blood, which makes it more difficult for blood to reach the brain.

During hyperventilation, a person breathes at a much faster rate than is normal or healthy. By doing so, the person breathes out carbon dioxide before the body has a chance to create more, leading to a rapid drop in the body's carbon dioxide levels, notes Healthline. Without enough carbon dioxide, the blood vessels narrow and oxygenated blood is unable to travel to the brain fast enough. Anxiety and panic attacks are among the most common causes of hyperventilation.