Only traces of protein should be found in the urine of normal individuals. The presence of proteins in the urine is a sign of kidney disease often caused by diabetes or hypertension. The earlier the kidney disease is diagnosed, the more effective the treatment will be. The search for proteins in the urine begins with the measurement of microalbuminuria, which can detect very small amounts of protein in urine. For higher urine protein levels, the microalbuminuria test is replaced by the measurement of total proteins in the urine, which includes, in addition to albumin, other proteins of clinical interest, such as antibody fragments sometimes called free kappa or lambda light chains, or Bence-Jones proteins.
Undetectable (uncalculated) levels are normal. Up to 0.15g/d is considered to be of little significance (physiological proteinuria). A slightly elevated level can be caused by infection, medications, vigorous exercise, pregnancy, diet, exposure to cold, emotional or physical stress, etc. A high level can be due to a renal or non-renal cause: hypertension, bone marrow disease (multiple myeloma), lupus, preeclampsia, etc. A level higher than 3g/d is consistent with nephrotic syndrome, a severe disease of the renal glomerulus.