Calcium
The most abundant mineral in the body, essential for bones, nerves, muscles and heart.
| Typical reference range | 8.6–10.3 mg/dL |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
About 99% of calcium is stored in bone. The small amount in blood, about half bound to albumin and half free (ionized), is tightly controlled by parathyroid hormone, vitamin D and calcitonin.
Why it matters
Abnormal blood calcium usually reflects a hormonal or kidney problem rather than diet. Persistent high calcium is often caused by primary hyperparathyroidism, which is commonly found incidentally on routine panels.
What a high result can mean
Common causes are primary hyperparathyroidism and cancer; others include excess vitamin D or calcium supplementation, thiazide diuretics, lithium, dehydration, prolonged immobility and granulomatous diseases such as sarcoidosis.
What a low result can mean
Low calcium often reflects low albumin (total calcium falls while ionized calcium is normal). True low calcium can result from vitamin D deficiency, low magnesium, hypoparathyroidism, kidney disease and some medications.
What affects the result
Correct for albumin (add 0.8 mg/dL for each 1 g/dL albumin below 4.0) or measure ionized calcium. Prolonged tourniquet use and dehydration can raise it. Interpret with PTH, vitamin D, albumin, phosphorus and magnesium.
Units and conversion
Usually reported in mg/dL.
- From mmol/L: multiply by 4.008 to get mg/dL
- From mEq/L: multiply by 2.004 to get mg/dL
Also called on lab reports
Ca, Calcium, Serum, Calcium, Total, Total Calcium
Related tests: Electrolytes & Minerals
This page is educational and does not replace advice from a healthcare professional.