On smaller amounts of the life insurance there may just be a non-medical declaration where you answer some health questions, and depending on whether or not anything health issue is declared there may be no medical testing.
If urine and / or blood is required, medical testing could include testing for bodily functions including protein and cholesterol levels.
The presence of raised levels of certain kinds, such as sugar in the urine would trigger more tests.
In addition, testing is done for nicotine and for traces of illegal drugs and STD's, among other things which may affect your health, and whether or not you are approved for the life insurance policy.
Also, there are some life insurance policies that do not require you to take any medical tests. Learn more about life insurance medical exams and who they work.