Definitely get retested if your results seem impossible. @Rarebear gave you a good link to answer your question. Even if a lab is audited, they still can make a mistake. Getting them to do it for free on a new blood specimen might be difficult.
One time I was having cultures done and I told the doctor, if they do it incorrectly and don’t follow your instruction I will not pay for the test. The doctor and her nurse looked at me like I was the biggest pain in the ass. I indeed am a pain, because I expect everyone to fuck up at this point, and I am sick of it. Well, the lab did not follow the doctors instructions; I was right. When I called the nurse to say I am not going to pay, she got defensive saying she wrote it up correctly. I don’t doubt she did, but PLEASE at least tell me I was right and give me a little acknowledgment after treating me like shit for even mentioning up front I won’t pay when they mess it up. My doctor did get the fees taken off, she said she would repeat the test. I never did the test again, because this is what it has become for me, a series of incompetence, I can’t take it anymore.
I have had blood test results that I thought were wrong on myself and my aunt. When they were run again the result was extremely different. But, we, I, paid for it to be redone, because the doctor didn’t believe they were wrong. Really depends on the doctor agreeng with you or not. I guess if you have a new set of tests run and the results are vastly different you can go back and try to get the first set of fees wiped out. You have to decide whether to use the same lab again, or a different one for the second set of tests. I think blood tests are rarely mixed up, but I obviously do think it can happen.