Blood test/Full medical checkup (for a tentative job).. do they testing for drugs or newly for serious illneses/disease?
*Curiosity kill the cat*
The employer often get a full set of tests since they are roughly the same cost as a more constrained series.
I know someone who had a liver enzyme abnormality (not a disease in recent times a freaky set of triglyceride levels). The company withdrew its opportunity offer until he proved he be not an alcoholic whose liver enzymes were ruined by cirrhosis of the liver.
It's entirely up to company policy. Comprehensive drug screen can be pretty pricey, so not every company wants to wage for them.