to get a work visa/residence permit you must do a medical exam twice once when your employer applies to get you the papers to get a work visa, the medical exam is usually done in your home country you just need a stamp saying you got it at a real medical center one that they could check if they wanted to.
so you got your work visa and are in china now the work visa is only 1 month so you must apply to get it changed to a residence visa you will need a medical check (about 400rmb) done in china at the hospital in kunming