Fibroblast Growth Factor 23 (FGF23) is a molecule that has been implicated in the homeostasis of phosphorus. Elevated FGF23 levels are well-documented in patients with Chronic Kidney Disease (CKD) and are inversely correlated with Glomerular Filtration Rate (GFR). FGF23 levels are also predictive of progression of CKD and predict mortality in CKD. Although studies in normal individuals suggest that phosphorus intake is related to FGF23 levels, the effect of dietary and pharmacologic phosphate restriction on FGF23 levels in patients with CKD has never been reported. Our objectives are to determine if phosphate reduction through the use of non-calcium based phosphate binder will decrease serum FGF23 levels. The investigators will also be investigating associations of elevation in FGF 23 levels with commonly encountered co-morbidities in CKD patients such as Coronary Artery Disease, Diabetes Mellitus, and Hypertension.

Inclusion Criteria:

• Adults between ages 18-80 years old, with a GFR less than or equal to 50 ml/min/1.73 m2 as determined by the Modification of Diet in Renal Disease (MDRD) formula will be included.

Exclusion Criteria:

• Patients will be excluded if they have a history of renal transplant or are pregnant. In addition, patients with dysphagia, swallowing disorders, severe GI motility disorders, severe constipation, history of major gastrointestinal surgery and patients taking levothyroxine for hypothyroidism will be excluded.