What Does Calcium Mean?
Calcium is essential for bones, muscles, nerves, and heart rhythm. Elevated blood calcium often points to parathyroid issues, vitamin D excess, or rarely cancer.
What Calcium Measures
Total calcium measures both bound and free calcium in blood. Most circulating calcium is bound to albumin, so albumin levels affect interpretation. Ionized calcium (the biologically active form) is more accurate when albumin is abnormal. Most body calcium is stored in bones — blood levels are tightly regulated by parathyroid hormone and vitamin D.
Normal Ranges
Normal (total)8.5–10.5 mg/dL
Low (hypocalcemia)< 8.5 mg/dL
High (hypercalcemia)> 10.5 mg/dL
Critical high (urgent)> 12 mg/dL
Reference ranges may vary slightly by lab. Always use the range provided on your specific test report.
What Affects Your Calcium Level
- Hyperparathyroidism (most common cause of high calcium)
- Vitamin D excess (over-supplementation)
- Certain cancers (breast, lung, multiple myeloma)
- Kidney disease
- Thiazide diuretics
- Prolonged immobilization
- Magnesium deficiency (causes low calcium)