Does Vasoconstriction affect Haemoglobin?

I've recently been drinking LOADS of coffee (which is apparently a vasoconstrictor) and ever since then my HB hasn't been too good. After two blood transfusion my Hb would only increase around 0.5-1.5 which kind-of scared me.

Do you guys have any idea if vasoconstriction affects the Hb?

Cheers,
Robert.