If your body is in trouble it will first try to defend you. It will work overtime. This will result in exhaustion and fatigue. This happens even when fatigue is nonspecific. Sometimes a specialist cannot diagnose the root cause of the issue at first sight. Deep vein thrombosis needs more detailed tests. Pay attention how you feel during the day and whether you get tired for no obvious reason. If your lifestyle is not very active and you do not practice sports or suffer from insomnia yet feel exhausted and tired most of the time, then it is very possible that the fatigue is clot-related.