Creatinine-based estimated glomerular filtration rate (eGFRcr) and cystatin C-based eGFR (eGFRcys) may be inaccurate for patients with rheumatoid arthritis (RA) due to sarcopenia and inflammation. This study characterized changes in eGFRcys and eGFRcr after 2 RA treatment regimens and their association with RA disease activity biomarkers.