The NURTuRE-CKD study examined the relationship of creatinine muscle index (CMI), calculated as eGFR cystatin C times serum creatinine concentration, with sarcopenia and mortality in 2930 patients with non-dialysis chronic kidney disease (CKD). Among 1723 men and 1207 women, median age was 66 years (IQR 53–74) and median eGFRcreatinine was 34 mL/min/1.73 m²; 27.5% had probable sarcopenia (hand grip strength <27 kg in men, <16 kg in women) and 18% died within 50 months (IQR 41–56). CMI was negatively correlated with probable sarcopenia: adjusted OR 0.72 (95% CI 0.67–0.78) in men and 0.81 (95% CI 0.73–0.89) in women for an increase of 100 mg/day. It was positively correlated with grip strength (ρ=0.47 in men, 0.45 in women) and negatively with the TUG test (ρ=–0.37 in men, –0.44 in women). Lower CMI was associated with higher mortality: adjusted HR 0.85 (95% CI 0.78–0.90) in men and 0.77 (95% CI 0.67–0.87) in women. CMI C-index for sarcopenia (0.73 in men, 0.71 in women) and mortality (0.70 in men, 0.76 in women) was higher than for eGFR ratio or difference (all p<0.001).