Calcium, Serum (Substance Concentration)
This test measures the amount of calcium, a mineral essential for strong bones, healthy nerves, and proper muscle function, in your blood serum.
["Your blood calcium levels help ensure your body’s vital functions stay balanced."]
Key facts at a glance
- LOINC
- 59569-4
- Short code
- CALCPOST
- Synonyms
- Calcit p chal SerPl-sCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top serum tube or SST (Serum Separator Tube)
- Units
- N/A
- Critical range
- — – 1000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- Chemiluminescent Immunoassay (CLIA) or Radioimmunoassay (RIA)
- CPT
- 82308
- SNOMED
- 3952009
- Specimen volume
- 1.0 mL serum minimum; 2.0 mL preferred for repeat testing
- Stability
- Stable for 4 hours at room temperature; 1 day at 2-8°C; may be frozen at -20°C or below for up to 6 months. Avoid repeated freeze-thaw cycles. Process and separate serum within 2 hours of collection.
- Hemolysis max
- 100
- Lipemia max
- 300
- Icterus max
- 25
- TAT
- 24–72 hours
- Order
- routine
Why Is This Test Done?
Your doctor may order this test to check for conditions affecting bone health, kidney function, or calcium metabolism. It can also help diagnose or monitor symptoms like muscle cramps, unusual fatigue, or unexplained bone pain.
What to Expect Before the Test
No special preparation is needed. You may have a small needle inserted into your arm or hand to draw blood. If you’re on blood thinners or have a history of bleeding issues, let your doctor know beforehand.
What the Results Mean
Results are typically reported as a numerical value (in mg/dL or mmol/L), but your doctor will interpret them in relation to your overall health. Very low or very high levels can signal underlying health concerns.
Common Conditions Monitored
This test is often used to evaluate conditions like hypoparathyroidism (low calcium), hyperparathyroidism (high calcium), kidney disease, or vitamin D deficiency, which can disrupt calcium balance.
Reference range
Reference ranges vary by stimulation agent, baseline value, and laboratory methodology. Post-stimulation calcitonin values are interpreted in conjunction with baseline levels. A calcitonin stimulation test (pentagastrin or calcium challenge) showing a rise to >100 pg/mL (males) or >80 pg/mL (females) is suggestive of medullary thyroid carcinoma (MTC). Values should be interpreted by an endocrinologist in clinical context.N/A
Fasting is not required, but an overnight fast may be preferred. Patient should be supine for at least 15 minutes prior to blood draw. Patient should remain in supine position throughout the stimulation test. No special dietary restrictions unless specified by ordering physician. Document time of blood draw relative to stimulus administration.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Serum Calcium
Frequently asked questions
What causes low calcium levels?
What causes high calcium levels?
How often should I get this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 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