Effects of Lanthanum Carbonate on FGF-23 in Subjects With Stage 3 CKD

Inclusion Criteria: Subjects meeting all of the criteria listed below may be included in the study: 1. ≥18 years old. 2. Male, or non-pregnant, non-lactating females who agree to comply with any applicable contraceptive requirements of the protocol. 3. Been in the care of a physician for CKD for \>2 months, and are not expected to begin dialysis for at least 6 months. 4. Screening serum c-terminal FGF23 \> 50.0RU/mL. 5. Screening estimated glomerular filtration rate (eGFR) of 30-59mL/min/1.73m2 using the MDRD formula. 6. Normal serum phosphate (0.808-1.55mmol/L). 7. Endogenous 25-hydroxy Vitamin D levels \>20ng/mL. 8. Adequate protein diet (includes 2-3 portions of protein-rich food per day). 9. An understanding, ability, and willingness to fully comply with study procedures and restrictions. 10. Ability to provide written, signed, and dated (personally) informed consent to participate in the study. Exclusion Criteria 1. Vitamin D supplementation required. 2. Compounds containing calcium, phosphate, aluminium or magnesium required. 3. Acute renal failure. 4. Rapidly progressing glomerulonephritis. 5. Vegetarian diet. 6. Known allergy to iodine. 7. Clinically significant uncontrolled concurrent illness, which, in the opinion of the Investigator, would impair subjects' ability to give informed consent or take part in or complete this clinical study. 8. Cirrhosis or other clinically significant liver disease (aspartate transaminase (AST) or alanine transaminase (ALT) \>3 times the upper limit of normal or bilirubin \>2 times the upper limit of normal). 9. Past (treated within the last 5 years) or present GI disorders including uncontrolled peptic ulcer, Crohn's disease (or other conditions where the integrity of the GI tract may be compromised), malignancy, or GI bleed within the last 6 months. 10. Life-threatening malignancy or current multiple myeloma. 11. Known to be Human Immunodeficiency Virus (HIV) positive. 12. History of poor compliance with diet or medication that in the Investigator's opinion may interfere with adherence to the protocol. 13. History of alcohol or other substance abuse within 6 months prior to screening. 14. Subjects must not have used another investigational medicinal product or taken part in a clinical trial within the last 30 days prior to enrolment. 15. Subjects who have previously been enrolled into this study and subsequently withdrawn.