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Calcium Blood Test: What Your Results Mean

Calcium is the most abundant mineral in the body and is essential for building and maintaining strong bones and teeth, enabling muscle contraction, supporting nerve transmission, and facilitating blood clotting. About 99% of calcium is stored in bones; the remaining 1% circulates in the blood where its concentration is tightly regulated by parathyroid hormone (PTH), vitamin D, and calcitonin.

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Normal Range

8.5 – 10.5 mg/dL

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Unit

mg/dL

What Your Results Mean

Normal

A normal calcium level indicates that the parathyroid glands, kidneys, and vitamin D system are working together effectively to maintain the right amount of calcium in the blood. Bone density and neuromuscular function are being properly supported.

High

High calcium (hypercalcaemia) is most commonly caused by primary hyperparathyroidism (overactive parathyroid glands) or cancer (bone metastases or tumours producing PTH-related protein). Other causes include excessive vitamin D supplementation, sarcoidosis, and prolonged immobilisation. Symptoms include fatigue, excessive thirst, frequent urination, constipation, and in severe cases, confusion and cardiac arrhythmias.

Low

Low calcium (hypocalcaemia) causes muscle cramps, tingling in hands and feet, spasms, and in severe cases, seizures and cardiac problems. Common causes include vitamin D deficiency, hypoparathyroidism, magnesium deficiency, kidney disease, and certain medications.

Frequently Asked Questions

What does high calcium mean? expand_more
High calcium (hypercalcaemia) is most commonly caused by overactive parathyroid glands or cancer. Other causes include excessive vitamin D, sarcoidosis, and some medications. Mild elevations may be asymptomatic, but significant hypercalcaemia requires medical evaluation and treatment.
What does low calcium mean? expand_more
Low calcium usually points to vitamin D deficiency, underactive parathyroid glands, magnesium deficiency, kidney disease, or calcium malabsorption. Symptoms include muscle cramps, tingling, spasms, and in severe cases, seizures.
What is the normal calcium level in blood? expand_more
Total blood calcium is normally 8.5 to 10.5 mg/dL. Ionised calcium (the active fraction) is also measured and has its own reference range. If albumin is low, corrected calcium should be calculated to get an accurate picture.
Why does albumin affect my calcium result? expand_more
About half of blood calcium is bound to albumin. If albumin is low, total calcium appears falsely low even though the active (ionised) fraction may be normal. Doctors use a formula to calculate "corrected calcium" to adjust for low albumin.
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