GDF15 and chronic kidney disease: The predictive value of diagnosing absolute IDA among CKD patients using GDF-15 was 74.02% (95% CI: 67.62–80.42%) while the predictive value of diagnosing functional IDA among CKD patients using hepcidin was 70.1% (95% CI: 62.79–77.49%).There was a weak negative correlation between hepcidin levels and GFR (r = − 0.19, p = 0.04) in anaemic CKD patients, and between serum GDF-15 and haemoglobin (r = − 0.34, p = 0.001).