Intel had me do a drug test just for an internship that I was almost going to take in 1996 or 97. I'm not sure if they still do that, I haven't had a drug test since getting my Chinese work visa (which required a drug and Aids test).
Canadian immigration wanted my full medical history for Permanent Resident status, and there was a medical check, blood work, and a chest xray for TB. I was in the US military with injuries from that, and they asked for all of the paperwork.
The civil surgeon is required to perform specific tests for tuberculosis, syphilis, and gonorrhea. The medical examination also requires the civil surgeon to evaluate for other sexually transmitted diseases and Hansen’s disease (leprosy).
Furthermore it suggests that physical and mental disorders may be grounds for disqualification. Finally, drug addiction and substance abuse generally must be disclosed.
https://www.uscis.gov/sites/default/files/document/forms/i-6...