Why is hematocrit higher in venous blood?

Question

(apparently its got something to do with the hamburger effect)

Answer 1

I haven't heard of anything called the Hamburger Effect, but I think the hematocrit is slightly higher in venous blood because blood flows from the arterial system into the venous system, and along the way there is some loss of plasma (the liquid part of blood) into the lymphatic system and water via the kidneys for the production of urine.  So it's not that there's actually more red blood cells, but since the volume is slightly contracted, there's a relative rise in hematocrit.

Alternately, I suppose it could also be that the blood picks up newly-created RBCs along the way, but I suspect it's more the first than the second.