Calcium
An essential mineral for bones, muscles, and nerves. Blood calcium levels are tightly regulated by parathyroid hormone and vitamin D.
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What is Calcium?
Calcium is the most abundant mineral in your body, with 99% stored in bones and teeth. The remaining 1% circulates in blood and is critical for muscle contraction, nerve signaling, blood clotting, and heart function.
Blood calcium is tightly regulated — even small deviations can cause serious symptoms. Your body maintains calcium levels by adjusting absorption, bone release, and kidney excretion.
Normal Ranges
| Type | Normal Range |
|---|---|
| Total calcium | 8.5–10.5 mg/dL |
| Ionized calcium | 4.5–5.3 mg/dL |
Ionized (free) calcium is the biologically active form and more accurate when protein levels are abnormal.
Why It Matters
Bone Health
Chronically low calcium intake forces your body to pull calcium from bones, increasing osteoporosis risk over time.
Parathyroid Function
Abnormal calcium often reflects parathyroid problems. High calcium with high PTH suggests primary hyperparathyroidism.
Medication Monitoring
Calcium levels need monitoring with certain medications and conditions, including kidney disease and some cancer treatments.
High Calcium (Hypercalcemia)
Causes include:
- Primary hyperparathyroidism
- Cancer (bone metastases, PTHrP production)
- Excessive vitamin D
- Certain medications
Low Calcium (Hypocalcemia)
Causes include:
- Vitamin D deficiency
- Hypoparathyroidism
- Chronic kidney disease
- Magnesium deficiency