Always always! retain a copy of your medical tests and results, and any letters that doctors may have written about you that may be on your file. Study them and read between the lines. Don't rely on any "verbal" communication as being the truth and the necessary course of action for any treatments you may be considering or that have been recommended to you. If you decide to switch doctors you have all records in your possession to take with you. Doctors are famous for charging ridiculous fees to transfer your records to another location. I have heard as much as $300 depending how "fat" your file is!
If your medical test results are consistently being "lost", you can almost assume you are part of some study they are doing behind the scenes!! Trust me on this as my lifetime records have been lost and were needed in a disability court case, and other results have been conveniently lost as the results did not make any sense in regards to their expectations. They will always cover their butts!!
And this last one I just love! When you have the whole picture in front of you it is really easy to see, that over time they will change the acceptable parameter range for say a blood test. By doing this they can now turn around and tell you that the most recent blood work you had done shows you are outside what is acceptable for optimum health and this gives them license to prescribe some drug that will no doubt contribute to your death.
Just my two bits!