What would happen if the following happened in a hospital. (Assume that this is the real world, where magic shouldn't exist.)
1) As usual when dealing with unknown poison / designer drug. Observe vital signs, treat blatantly wrong things like too high / too low pressure. Hope that the patient would survive.
2) Ask your superior what to do with with this complicated case, as specified in procedures. (nice way of passing a problem)
3) Apply a wide range of possible tests. (partially hoping to get any useful info, partially just to avoid doing nothing)
4) No one would like to make a phone call for any police... As such call would be ignored as a prank or a call made by a psychotic patient.
5) While waiting for lab tests to be produced deal with next, more urgent patients. (it tend to be busy in emergency rooms)
The shape shifting wrapper can encompass a number of different apparently magical wonders and a hospital full of scientists (and other worshippers of cause & effect) might have drastically different responses, depending on which wonders are immediately apparent.
If the patient transforms into a creature of drastically different mass and if the transformation does not make up for that mass by either absorbing or excreting appropriate quantities of matter; then a fundamental law of physics is being broken. You can expect the scientists to get a little emotional once you've violate conservation of mass and energy.
Similarly, if all of the patients clothing and possessions vanish while they are in animal form and reappear during their journey back to being bipedal; then a lesser known fundamental law joins CoM&E on the butcher block. Because that is the destruction and reconstruction of information and a slap in the face of entropy. Expect more pissed-off PHDs after that performance.
But if your shifter is well behaved and at least appears to be obeying the laws of nature, if he carefully disrobes before his bones and muscles begin changing into a comparably sized creature; then you can expect the surrounding professional care givers to show patience, curiosity and kindness as they support, comfort and study this afflicted soul.
They will probably even give him a strong comforting sedative before the dissection begins.
Your average ER would freak out. I mean seriously freak out. Granted, if the shapeshifter turned into a bunny, the freaking wouldn't be so great as if it were a more aggresive creature, but there would be freaking. And I doubt it would be as cultured as Fonzie meeting Mork freaking.
And when they were done freaking, there would be police... lots and lots of police. Who would then freak.
At this point you have a 50/50 chance. They might tase the shapeshifter, or they might shoot it. Shooting it isn't very fun, let's tase it.
Once the shapeshifter is subdued, it would be caged. Having determined the minimum bar spacing from the animal (a rabbit would need, what, 2" spacing?) an appropriate cage would be constructed. At which point the local university would be called to investigate the creature.
They'd freak.
But not before the yet-to-be-announced-by-Snowden big brother of Cyberhawk is used by the NSA to intercept the call, identify the phrase, "it's a freaking monster!" and react by dispatching NSA agents, who are inevitably dressed in black and drive unmarked and unlicensed SUVs.
They don't freak.
They very politely take posession of said shapeshifter, neuralyze everyone so they don't remember what happened, leave them with a passible subliminal message about what caused the mess (light reflecting off of venus cast a bunny-shaped shadow on the wall, causing that nurse over there to freak. Maybe she needs counselling for her leporiphobia.), and leave.
After which your shapeshifter begins to freak.
About two years after that Guillermo del Toro would create a movie loosely based on the incident with remarkably slender oriental women playing nurses and equally remarkably buff Australian men playing the NSA agents with a 3-tone musical score you can't keep out of your head and make bazillions of dollars — not one penny of which will go to your shapeshifting rabbit.
This probably wasn't the answer you were looking for... but I couldn't help myself.
Well if he just turned into an animal in front of everyone, then(assuming the doctors want to help him) the doctors will probably board up the doors(for the hoards curious about the animal shape shifting) and clear out all the patients on the same floor in 100 ft radius(to prepare for the worst, a blue whale transformation) and curing the poison should be easy or hard with a shape depending on whether or not he can control the animals he is uncontrollably turning into. If he keeps turning into animals smaller than a human then the doctors will have a bad time treating him, fist off the amount of treatment will change with size(if he become a fairyfly well good luck) , what to use will change with what he is(different biochemistry), and the tools based on what he is as well. So I'm saying a quick trip to the local vet to pick up what is needed and a vet(being a vet is actually so hard that many drop out to become doctors). If Sea World is at a reasonable distance then maybe pick up someone from their or a Zoo for the more exotic transformations. And if he turns into animals that are larger than a human, well congrats, your cured! the poison will be processed better by bigger animals, and super well if you become a Blue Whale, just don't stay too long or you will look like this
It's going to depend on how the doctor reacts to the fact that his entire world view has just been broken by having the existence of magic/the-really-freaking-strange-unknown, shoved down his throat. But fair bet, the CDC gets called and the hospital gets evacuated and the doctor doesn't actually treat the patient.
Recall that one lecture on One Health from medical school. Failing that call a veterinarian. ;)
