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 following two RA treatment regimens and their association with RA disease activity biomarkers.