Disclosed is an iron metabolism-improving agent for improving the iron metabolism in the body of a patient having chronic renal failure who is receiving a blood purification therapy such as hemodialysis, hemofiltration and hemodialysis filtration. The iron metabolism-improving agent does not contain acetic acid and/or an acetic acid salt as an electrolyte, comprises citric acid and/or a citric acid salt, and further comprises other electrolyte(s) and glucose alone or in combination. The iron metabolism-improving agent is in the form of a dialysis fluid and/or a substitution fluid for dialysis. Also disclosed is a method for improving the iron metabolism in a living body by using the dialysis fluid and/or the substitution fluid for dialysis. Further disclosed is a blood purification method including hemodialysis and hemodialysis filtration for a patient having chronic renal failure.