How common is it to spill protein in your urine for days after a workout?

Small amounts nl: Many athletes have trace or 1+ protein in urine. It has to do with muscle cell metabolism and breakdown during exercise, especially if very vigorous or harder than usual exercise. A good trick is to check a first morning urine - that should have less protein and if so, then the protein showing up in your urine is probably not a big deal. Just discuss with your doc at nest visit, but wouldn't worry.