PATIENT PREPARATION FOR BLOOD TESTS One of the most important factors in determining the accuracy and reliability of your lab test is you, THE PATIENT. After all, it is a sample from your body (blood, urine, or some other specimen), on which the test will be performed. Therefore, it is essential that you do the following to ensure that the results will be useful and interpreted correctly by your doctor: It should be noted that many tests require no special preparation. But for those that do, be certain to adhere to the instructions provided.