Figure 20-12 Relationship between serum creatinine and glomerular filtration rate (GFR). The relationship between serum creatinine and GFR as measured by creatinine clearance is reciprocal and exponential. Doubling of serum creatinine corresponds to halving of the GFR. Relatively large declines in GFR from normal are associated with small increases in serum creatinine until the GFR decreases below 60 mL/min; further decrements are associated with large increases in serum creatinine. (From Alfrey AC, Chan L: Chronic renal failure: Manifestations and pathogenesis. In Schrier RW [ed]: Renal and Electrolyte Disorders, 4th ed. Boston, Little, Brown, 1992, p 541.)