It depends on a few factors, but some things are pretty consistent. Yes, BUN and Creat will be elevated for a bit directly after working out, but not too long. Those levels seem to stay consistent unless you have some kidney issues underlying. The most prevelant blood test to elevate post traing is your CK levels. Stands for Creatine Kinase. This enzyme is readily broken down in muscle skeletal tissue which is what we do as bodybuilders. We break down the muscle so it can rebuild it larger and larger.
My buddy and I do our labs and joke about who is working out harder. LOL. The higher the CK number the harder you work out!! Mine is always higher than goodness. HAHAHA!!!
But, I have a buddy who competes and I ran his labs last weekend. His CK was almost double what ours usually runs...LMAO!!!! Gotta work a little harder I guess