Which supplement is indicated in chronic renal failure to maintain adequate calcium levels?

• A. Vitamin C
• B. Vitamin B12
• C. Calcium carbonate
• D. Magnesium phosphate

Answer: (C)

Chronic kidney disease disrupts calcium and phosphate balance because the damaged kidney can’t activate enough vitamin D and can’t excrete phosphate efficiently. This tends to lower serum calcium and raise phosphate, promoting secondary hyperparathyroidism and bone disease. A calcium-containing phosphate binder helps address both issues: it provides calcium to help maintain serum calcium levels and binds dietary phosphate in the gut to prevent its absorption. Calcium carbonate is commonly used for this purpose, making it the appropriate supplement in this scenario. Vitamin C and B12 don’t directly influence calcium management, and magnesium phosphate isn’t used to raise calcium levels and can worsen mineral imbalance in renal failure.