This question was discussed by Kyle Hill in his early video on the scene in Days of Future Past in which Magneto rips out iron from the security guard. He begins by noting that the large majority of a person's iron is bound in hemoglobin, and nearly all of the rest in proteins in the spleen, bone marrow, and liver.
Iron bound in hemoglobin is somewhere between weakly diamagnetic and weakly paramagnetic. Solid iron is one of the most magnetic materials — hence the name of that category being ferromagnetic. There's 9-10 orders of magnitude difference between how responsive bound iron is to a magnetic field and how responsive solid iron is. Additionally, you'd have to output a magnetic field capable of overpowering the covalent bonds. I'm sure you can already see why this is going to be difficult.
To put actual numbers to this, Kyle poses the following reference points:
- 1T: Nothing. This is your average refrigerator magnet. Enough to wipe his credit cards, maybe.
- 8T: Enough that if your target moves, he might have a sensation of metal taste in his mouth, see flashes of light, or feel weird on his legs. This has nothing to do with iron; rather, the magnetic field induces an electric current in the target, which stimulates his nerves.
- 16T: Scientists with way too much time on their hands have experimental evidence that frogs can be levitated at this field strength, and still live to croak the tale. The security guard is still tasting metal and seeing stars.
- 50T: Probably enough to levitate the guard off the ground.
- 100T: Either he'll die immediately of cardiac arrest (assuming the mental shock from everything else didn't already) from the magnetic field inducing a strong enough current to stop his heart, or he'll die later of DNA mutations as the magnetic field interacts with it on a molecular level.
- 10kT: Yes, kiloTeslas. That's enough to unwind his DNA.
- 100kT: The atoms in his body are so deformed that instead of being fuzzy spheres, the electron clouds are stretched into oblong ellipsoids. Chemistry doesn't work properly anymore. The iron is still covalently bonded to his hemoglobin, but if your target is somehow still alive by this point, he's dead now.
- 1.0MT: At 1 million Teslas, your target is no longer a human, not even a human corpse. It's more like a levitating blob of organic mush. The blob separates into a few smaller blobs, differentiated by subtle molecular differences in how they respond to magnetic fields (Kyle skips over the details, but I'm going to appeal to molecular orbital theory I think to explain this one.)
- 10MT: Finally the magnetic field can overcome the covalent bonds and rip the iron out of the now-blobified former human. For reference, this is roughly the magnetic field outputted by a neutron star; everyone within a few hundred kilometers is at best dead and at worst similarly blobified (probably Magneto included).
I haven't even gotten into the fallout of this; Kyle doesn't discuss things like the magnetic field interacting with the electric grid, or causing an EMP shockwave, or possibly messing with LEO satellites. Even if you're far enough away to survive, your credit cards are still wiped. Californians might survive, but they'll be seeing stars and tasting iron.
TLDR: Technically it's possible, but you'd need a homemade neutron star to pull it off. Also, it has a seriously large area of effect.