Why does the world go black when standing up after squatting for a long time?

Feeling dizzy or seeing black spots upon standing after squatting for a long time may result from normal physiological responses, orthostatic hypotension, or anemia.

1. Normal physiological phenomenon

Under normal circumstances, prolonged squatting causes blood to pool in the lower limbs. When a person stands up suddenly, the blood cannot return to the heart quickly enough, and if blood pressure does not promptly adjust to normal levels, this phenomenon may occur.

2. Orthostatic hypotension

When the body transitions from a squatting to a standing position, low blood pressure can lead to simultaneous ischemia in both occipital lobes of the brain and may even cause retinal hemorrhage due to insufficient blood flow in the bilateral ophthalmic arteries, resulting in temporary vision darkening upon standing after prolonged squatting.

3. Anemia

Anemia reduces oxygen and blood supply to the brain. After prolonged squatting, this insufficient cerebral perfusion may trigger episodes of visual darkening upon standing.

In elderly individuals, such symptoms may be caused by weakened vascular regulatory function due to chronic conditions such as hypertension, diabetes, or hyperlipidemia.