Yes.  Ferrets have no apparent blood types, so if your ferret needs a
transfusion any other ferret can be a donor -- the bigger, the better.
Dr. Susan Brown writes, "Approximately 20 ml of whole blood can be
removed by cardiac puncture from a healthy male ferret weighing 1 kg
[2.2 lb] with no side effects; it can then be used immediately for
transfusing.  12 cc may be removed from a female weighing .75 kg [1.6
lb]."

If your ferret is going in for extensive surgery, ask your vet whether
it might be a good idea to also bring along a big, healthy ferret as a
potential blood donor, just in case it's needed.