Calcium (Blood)
Also known as: Serum calcium, Ca test, calcium test, calcium ki kami test
Measures calcium in the blood. Calcium keeps bones strong and is needed for nerves, muscles and the heart. About half of it is bound to albumin, a blood protein.
Why it's ordered
Checking bone and parathyroid problems, kidney disease, vitamin D deficiency, some cancers, and symptoms such as tingling, muscle cramps, tiredness or kidney stones.
Preparation
Usually no fasting needed. Tell your doctor about calcium, vitamin D and antacid tablets you take.
Typical adult values
| Total calcium | about 8.5–10.5 mg/dL (2.15–2.60 mmol/L) |
|---|---|
| Ionised (free) calcium | about 4.6–5.3 mg/dL (1.15–1.32 mmol/L) |
Ranges vary between labs and methods. Always use the range printed on your report.
If it's high
High calcium is most often caused by an overactive parathyroid gland or, less often, cancer, too much vitamin D, or some medicines. Very high levels can cause thirst, confusion and constipation and need urgent care.
If it's low
Low calcium is often caused by low albumin, vitamin D deficiency, kidney disease or low magnesium. It can cause tingling around the mouth and fingers and muscle cramps.
Good to know
If albumin is low, total calcium can look falsely low; labs often report an 'adjusted' (corrected) calcium. A sample contaminated with EDTA from a blood-count tube can give a falsely very low calcium, so unexpected results are usually repeated.
Common questions
What is a normal calcium level?
Total calcium is typically about 8.5–10.5 mg/dL (2.15–2.60 mmol/L). Always use the range printed on your report.
Why do labs report adjusted calcium?
If albumin is low, total calcium can look falsely low, so labs often report an 'adjusted' (corrected) calcium.
What are the symptoms of low calcium?
Low calcium can cause tingling around the mouth and fingers and muscle cramps.
What causes high calcium?
Most often an overactive parathyroid gland or, less often, cancer, too much vitamin D, or some medicines.