Low blood calcium (hypocalcemia) is different from simply having low dietary intake. Common causes include vitamin D deficiency (reduced absorption), parathyroid hormone (PTH) problems, kidney dysfunction (affecting vitamin D activation and mineral balance), and low magnesium. Certain medications and acute illnesses can also disrupt calcium balance. Meanwhile, many people maintain normal serum calcium while bone stores decline due to low intake—this is a silent process. Therefore, evaluation should include albumin, ionized calcium, vitamin D, PTH, magnesium, and kidney function. Symptoms such as muscle spasms, numbness/tingling, or palpitations warrant prompt medical assessment. Treatment is cause-directed; taking calcium randomly may not resolve the underlying mechanism.