Vitamin D deficiency: This is often the most common cause of hypocalcemia, especially in populations with limited sun exposure, inadequate dietary intake, or malabsorption. Vitamin D plays a crucial role in calcium absorption from the gut.

Hypoparathyroidism: A condition where the parathyroid glands are underactive or have been removed, leading to insufficient production of parathyroid hormone (PTH), which is essential for maintaining normal calcium levels.
Chronic Kidney Disease (CKD): CKD can lead to hypocalcemia due to impaired activation of vitamin D, reduced calcium absorption, and increased phosphate levels, which can lower calcium levels.
Magnesium deficiency: Magnesium is important for the release of PTH and the activation of vitamin D. A deficiency can lead to hypocalcemia that is resistant to treatment with calcium and vitamin D alone.

Medication-induced hypocalcemia: Certain medications like bisphosphonates, denosumab, and cinacalcet can cause hypocalcemia. Recognizing and managing these cases is crucial to prevent severe complications.
Hungry bone syndrome: This condition occurs after parathyroid surgery, where bones rapidly take up calcium, leading to severe hypocalcemia. It's critical to anticipate and manage this condition post-operatively.

Pseudohypoparathyroidism: A rare genetic disorder characterized by resistance to PTH, leading to hypocalcemia and hyperphosphatemia.
Barter syndrome and Gitelman syndrome: Rare genetic disorders affecting the kidneys, leading to hypocalcemia among other electrolyte imbalances.
Osteoblastic bone metastases: Certain cancers, like prostate cancer, can metastasize to bone and cause an osteoblastic reaction, leading to increased calcium deposition in bone and hypocalcemia.