Calcium Blood Test
A calcium blood test measures the amount of calcium in your blood to help your doctor evaluate bone health, nerve signaling, muscle function, and heart health.
{"A calcium blood test measures the total calcium or ionized calcium in your bloodstream","Normal blood calcium levels are typically between 8.5-10.5 mg/dL","This test helps diagnose conditions affecting bones, kidneys, and parathyroid glands","Abnormal levels may indicate vitamin D deficiency, kidney disease, or parathyroid disorders","The test requires a simple blood draw and fasting may be recommended"}
Key facts at a glance
- LOINC
- 17861-6
- Short code
- Ca
- Synonyms
- —
- Category
- electrolyte
- Sample
- serum
- Container
- Red Top Tube (Plain) or Serum Separator Tube (SST)
- Units
- mg/dL
- Ref low
- 8.5
- Ref high
- 10.5
- Critical range
- 6 mg/dL – 13 mg/dL
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–150 years
- Method
- o-cresolphthalein
- CPT
- 82310
- SNOMED
- 363006005
- Specimen volume
- 3-5 mL
- Stability
- Room temperature: 8 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C): 3 months
- Hemolysis max
- 50
- Lipemia max
- 300
- Icterus max
- 20
- TAT
- 1–4 hours
What is this test?
A calcium blood test measures the amount of calcium in your blood. Calcium is an essential mineral that plays a critical role in bone health, muscle contraction, nerve function, and blood clotting. Your body carefully regulates calcium levels through hormones including parathyroid hormone (PTH) and vitamin D.
Why is this test performed?
Your healthcare provider may order a calcium blood test to: check overall health during routine checkups, evaluate bone diseases such as osteoporosis, monitor kidney function, assess parathyroid gland function, investigate symptoms like muscle cramps, weakness, or confusion, or monitor certain cancer treatments that may affect calcium levels.
How is the test performed?
A healthcare professional will draw a small blood sample from a vein in your arm. The procedure takes only a few minutes. You may need to fast (not eat) for 8-12 hours before the test, depending on your doctor's instructions. Be sure to inform your healthcare provider about any medications or supplements you are taking, as some can affect calcium levels.
Understanding your results
Normal blood calcium levels typically range from 8.5 to 10.5 mg/dL. Your results may vary slightly depending on the laboratory. Both high and low calcium levels can indicate underlying health conditions that require further evaluation. Always discuss your results with your healthcare provider who will interpret them based on your overall health and medical history.
Reference range
Adult: 8.5-10.5 mg/dL. Pediatric ranges vary by age: Neonates (7.0-12.0 mg/dL), Infants (8.5-11.0 mg/dL), Children (9.0-11.0 mg/dL). Reference ranges may vary slightly by laboratory methodology.mg/dL
No special preparation required. Avoid prolonged fasting (>12 hours) as it may artificially lower calcium levels. Patient should inform healthcare provider of any calcium supplements or vitamin D medications being taken. Recent intravenous fluid administration may affect results.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
High blood calcium (hypercalcemia) may indicate hyperparathyroidism, cancer, vitamin D excess, or certain medications. Symptoms include fatigue, nausea, confusion, and kidney stones. Low blood calcium (hypocalcemia) may result from vitamin D deficiency, kidney disease, hypoparathyroidism, or low albumin. Symptoms include muscle cramps, tingling in fingers, and seizures in severe cases.
The calcium test is often ordered alongside other electrolyte panels and tests for vitamin D, phosphorus, and parathyroid hormone to provide a complete picture of your mineral metabolism. This helps healthcare providers diagnose and monitor conditions affecting bones, kidneys, and the parathyroid glands.
Short name
Ca
Part of panels
Frequently asked questions
Do I need to fast before a calcium blood test?
Can my diet affect calcium test results?
What happens if my calcium levels are abnormal?
Are there any risks from the calcium blood test?
How often should I have my calcium levels checked?
Sources
- 1
- 2
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 10, 2026. · Read our editorial policy