A Crossover Safety Study of Ferumoxytol Versus Placebo

Inclusion Criteria: * Male or female patients \> 18 years. * Have chronic kidney disease per K/DOQI guidelines. * Baseline hemoglobin of \> 9.0 and \< 12.5 g/dl Exclusion Criteria: * Women who are pregnant or lactating. * Received another investigational drug or device within 30 days. * Recent parenteral or oral iron therapy. * Patients that have other causes of anemia. * Major surgery within 30 days or anticipated or planned surgery during the study. * Patients with active infections. * Recent blood transfusions. * Patients with known allergies to iron products.