The accuracy of laboratory test results is closely related to the quality of the samples taken. The samples taken must be representative of the conditions existing in the patient’s body, and the results of the tests must reflect the pathological state of the patient’s body. Therefore, the preparatory work before the laboratory test is very important and must be emphasized so that the validity of the results can be ensured and unnecessary re-sampling or re-checking as well as possible misdiagnosis can be avoided. For example, when retaining a semen sample, the length of abstinence, the time from obtaining the semen to delivering it to the laboratory, spilling a portion of the semen or contaminating it, etc., will all affect the accuracy of the test results. In clinical practice, there are certain time requirements for sample collection, as is the case with blood samples used for hormone testing. Due to the hormone secretion has circadian rhythmic changes, generally take the morning fasting samples sent to the test, the so-called fasting, refers to the previous day after dinner, no longer eat food, but can drink water as usual, to the next morning around 8:00 to collect samples. This is because: 1, the laboratory to provide a variety of tests for the normal reference value of the project, is basically the extraction of normal people’s fasting blood, after testing and statistics to determine, in order to make the test results are comparable, as far as possible, under the same conditions for comparison, because many components of human blood are dynamically changing over time; 2, the human body after a night’s rest, the body’s composition to achieve a relatively dynamic equilibrium with less fluctuation; 3, as the detection process of many examination items is affected by the sugar and fat components in the blood, which are greatly affected by diet, and, moreover, the rate of lipemia is high after diet, so that the serum or plasma will be turbid, which will seriously interfere with the test results of many items, and even give wrong results, leading to misdiagnosis. Therefore, in order to ensure the accuracy of the results of hormones, etc., fasting blood must be used.