Do I have to get some blood tests before doing a thoracentesis?

Yes. A doctor will usually want a few simple blood tests to make sure you do not have some potential for bleeding prior to a thoracentesis. It depends a lot on what medications you are currently taking, especailly blood thinning medications and your general level of health at the time of the thoracentesis. A protime test and a blood count are typical tests to do prior.