I've been trying to find the title to this movie for a while now. I don't remember the actors, but do remember some of the story and that it was a comedy. A man went to the doctor to get tests done including blood drawn. At the same time a man down the hall was getting the same thing done. I do remember that this second man was a bus driver and when he left the room he switched his blood sample with the first mans. The first man is then diagnosed with a terminal illness. He then begins taking all sorts of life threatening risks trying to end his life before the illness does, only to later find out that his blood samples were switched at the doctors office. I think that all came about after the bus driver was involved in a accident. I'm not 100% sure when this movie came out, but for some reason I want to say it was in the late 80's.

Here it is. This movie is a classic!

The bus driver was there for a random drug test for his work, and as had been smoking pot he switched the samples so he wouldn't lose his job. Dabney Coleman was the Cop who wanted his family to receive an insurance payout, hence his attempts at dying in the line of duty.

Short Time (1990) - Full cast and crew (http://www.imdb.com/title/tt0100604/fullcredits#cast)

Thanks gekko I've been searching for this for along time. I was beginning to thank that I would never find it. Thanks again!