In the past (and still for some areas of China), Chinese immigration expected teachers to get a physical exam/medical check/blood test/x-rays before issuing the work visa (z-visa). For most areas now Chinese immigration can accept a signed letter from the teacher saying that they do not believe they have any medical issues and then do the medical check once they get to China.
For the medical exam teachers cannot eat/drink anything from the night before (not supposed to drink water also).
Lately the test has taken about an hour or two to get through. This is needed for the residency permit (which needs to be submitted shortly after arrival), so the medical check is often done on the second or third day after you arrive.
The medical check is done in modern, clean, professional hospitals (there has yet to be any complaint from a teacher contrary to this).
For complaints, I would say 50% of the female teachers have no issue with the test but 50% will say it was uncomfortable. Everyone agrees that it is usually very efficient, you go from station-to-station and it seems very sterile, not personal at all, when they move you around for the tests.
I believe all of the male teachers say that the medical test is perfectly fine, they like the efficiency and are glad at how they get you in and out of there quickly.
1. They do a urine sample. We have had one teacher that had to be there for the whole morning as they went to the washroom right before forgetting about this fact.
2. One teacher was on a lot of medication and was worried about if the results of the tests would indicate that and prevent her from getting a visa. -> There was no issue at all.