What does it mean to not have visible veins anymore, from a circulatory standpoint?

Veins gone: Either they are better or you have gotten so fat they can no longer be seen.

Visible veins.: The function of the veins is to return blood from the body back to the heart. Veins have the capacity to increase and decrease the amount of blood that they can carry depending on many factors such as levels of hydration, outside temperature, level of exertion, hormones and even genetics. Therefore, veins will change in size and ability to see them as a normal occurrence.