is the presence of protein (albumin) in the urine.  There are different types of proteinuria including glomerular, tubular, overflow, and post-renal. Glomerular proteinuria is the most common type.

It is not always related to an underlying condition such as kidney disease.  Normally, there is very no protein present in your urine. The kidney’s good filtration barrier prevents proteins from leaving the blood, and proteins that manage to make it through the filtration barrier signify pathology.