Is my Calcium (Serum) normal?
Free blood test checker · Standard + longevity-optimal ranges
What is a normal Calcium level?
Serum calcium is tightly regulated by the body — even small deviations can be significant. It's essential for bone health, muscle contraction, nerve signaling, and blood clotting. Most blood calcium is bound to albumin, so low albumin can falsely lower calcium readings. Normal range is approximately 8.6-10.3 mg/dL.
| Range | Values |
|---|---|
| Standard Reference | 8.6–10.3 mg/dL |
| High Risk | > 11 mg/dL |
| Low Risk | < 7.5 mg/dL |
What causes abnormal Calcium levels?
High calcium (hypercalcemia) is most commonly caused by overactive parathyroid glands (primary hyperparathyroidism), cancer, excess vitamin D, medications (lithium, thiazides), and dehydration. Low calcium (hypocalcemia) is caused by vitamin D deficiency, hypoparathyroidism, chronic kidney disease, magnesium deficiency, and malabsorption.
When should you see a doctor?
See your doctor if calcium is above 10.3 mg/dL or below 8.6 mg/dL on repeated testing. Symptoms of high calcium include fatigue, kidney stones, bone pain, confusion, and excessive thirst. Symptoms of low calcium include muscle cramps, tingling, and numbness. Always test PTH alongside calcium.
Calcium and longevity
Serum calcium is one of the most tightly regulated values in the body — the parathyroid glands constantly adjust PTH to keep blood calcium within a narrow range, even at the expense of leaching calcium from bones. This means serum calcium can appear "normal" while bone density is declining (osteoporosis). Persistently elevated calcium (hypercalcemia) is most often caused by primary hyperparathyroidism, which is curable with surgery but frequently missed. In the longevity context, calcium must always be interpreted alongside vitamin D (which promotes absorption), magnesium (which regulates PTH), and vitamin K2 (which directs calcium to bones rather than arteries). Excessive calcium supplementation without K2 may increase arterial calcification risk.
Where to get a Calcium test
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Related biomarkers
These biomarkers are often tested alongside Calcium for a more complete picture.
Frequently asked questions
What is a normal calcium level?
What causes high calcium?
Is a calcium blood test the same as a bone density test?
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Sources: Reference ranges based on AHA/ACC, ADA, and AACE clinical guidelines. Biological variation data from Ricos/Westgard database. Longevity-optimal ranges reflect targets used by preventive and functional medicine practitioners.
Last reviewed: April 2026. This tool provides general health information and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider about your specific results.