Is there as material that can block magnetic fields?

Question

And when you hold a magnet, won't it attract the iron in your blood?

Answer 1

Ferromagnetic material with high saturation and permeability.

You can use galvanized steel.

Try a search on "Magnetic Field Shielding"

Yes, holding a magnet will attract the iron in your blood, but iron is bound in huge hemoglobin molecules in low concentration. I think that the pumping force of the blood easily overcomes the magnetic attraction.

Answer 2

Redirect and concentrate the field, yes, block the field, no.

Good question on the magnet as it relates to iron in the blood. I don't know the answer to that one - I'll check back and see what your other answerers come up with.