Inadequate Blood Supply

The most common cause of poor circulation is underlying venous insufficiency, also known as vein disease. This condition develops when vein valves become damaged, allowing blood to flow in the opposite direction. Healthy blood flow travels through your veins from your legs up towards your heart.

Diseased vein valves allow blood to pool, which causes decreased circulation. Over time, the blood that pools within your legs can cause painful symptoms, inflammation, and put you at risk for serious health issues.
https://www.usaveinclinics.com/blog/can-poor-circulation-be-reversed/