Utilization of the Cockroft-Gault formula (Figure 1, above) allows for an accurate estimation of the creatinine clearance in these patients.9 For example, a 25-year-old man and an 85-year-old man, each weighing 158 pounds and having a serum creatinine value of 1 mg per dL, would have different estimated creatinine clearance even though their serum creatinine value is the same. The younger man would have an estimated creatinine clearance of 115 mL per minute, while the older man’s would be 55 mL per minute.