Calcium (Ca)
Calcium is the most abundant mineral in the body — 99% is in bones and teeth, and 1% circulates in blood. Blood calcium is tightly regulated because it is critical for muscle contraction, nerve signaling, heart rhythm, and blood clotting. Total calcium includes protein-bound and free (ionized) forms; ionized calcium is the active form.
Reference Ranges
Male
8.5 – 10.5
mg/dL
Female
8.5 – 10.5
mg/dL
Child
8.8 – 10.8
mg/dL
Ages 1–18
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
Low calcium (hypocalcemia) causes muscle cramps, tingling in fingers and lips, numbness, and in severe cases seizures or cardiac arrhythmias. Common causes include vitamin D deficiency (very common in India), hypoparathyroidism, kidney disease, and low albumin (which falsely lowers total calcium).
What High Levels Mean
High calcium (hypercalcemia) causes fatigue, confusion, constipation, excessive thirst, frequent urination, and kidney stones. The two most common causes are primary hyperparathyroidism and cancer (which can release calcium from bones). Mild hypercalcemia is often found incidentally on routine testing.
Frequently Asked Questions
Can low vitamin D cause low calcium?
Yes. Vitamin D is essential for calcium absorption in the intestines. Vitamin D deficiency — extremely common in India despite abundant sunlight — leads to poor calcium absorption, low blood calcium, and eventually weakened bones (osteoporosis or osteomalacia). Supplementing vitamin D often corrects calcium levels.
Why is total calcium affected by albumin?
About 40% of total calcium is bound to albumin. When albumin is low (liver disease, nephrotic syndrome), total calcium appears low even though ionized (active) calcium is normal. Doctors use a corrected calcium formula or measure ionized calcium directly.
How much calcium do I need daily?
Adults need 1000 mg/day (1200 mg for women over 50). Good sources include milk, curd, paneer, ragi (finger millet), sesame seeds, and green leafy vegetables. If dietary intake is insufficient, supplements may be recommended — always with vitamin D for proper absorption.
This information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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