Low-protein diet may give low clearance values. In prerenal uremia, there is fall
in urea clearance. Increase in renal failure decreases clearance value. The clearance
may fall to 50% of normal, while plasma urea will be within normal range. With
further reduction in clearance, plasma urea levels rise. With more severe renal
failure, the clearance may be less than 20% of normal.
17.6 Clinical Significance 73