All of the above. First, you need a baseline to compare to. Second, if you have any pre-existing conditions, they will come out in the baseline testing. All pathology needs to be addressed BEFORE you start an AAS cycle. third, you will see if you have sufficient natural testos production to support your gains. Second, retest around week six of AAS cycle. You will see how the AAS affects your body. With this info, you can make intelligent adjustments to your cycle. Lastly, after pct, to see if you have recovered.