My 91 y old mother’s creatinine level is 1.29 mg/dl (114 umol/L) ( lab. reference range 50-98umol/L)), Cystatin C 2.40 mg/L (0.40-1.20 lab range), uric acid 9.45 mg/dl (562 umol/ L) (150-400 lab. range. Calculated eGFR is 39 with creatinine level, but with Cystatin C value is only 20. Which eGFR should I use for medications dosages?

The Food and Drug Administration (FDA) recommends using the Cockroft Gault formula for calculating the creatinine clearance in dosing of drugs.  You can access the CG formula at:

The other two formulas are used to more accurately calculate estimated glomerular filtration rate (eGFR) but the CG formula has been used for calculating drug dosing for many more years.


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