Which of the following is NOT a phosphate binder?

• A. Vitamin B12
• B. Calcium carbonate
• C. Sevelamer
• D. Aluminum hydroxide

Answer: (A)

Phosphate binders work in the gut to trap dietary phosphate so it isn’t absorbed and can be excreted in stool, helping control hyperphosphatemia in kidney disease. Calcium carbonate binds phosphate in the intestinal lumen, forming insoluble calcium phosphate that’s excreted. Sevelamer is a non-calcium binder that also binds phosphate in the gut. Aluminum hydroxide binds phosphate as well, though its use is limited by potential aluminum toxicity with long-term use. Vitamin B12, by contrast, is a vitamin essential for red blood cell formation and nerve function and has no role in binding phosphate in the gut. Therefore, Vitamin B12 is not a phosphate binder.