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Calcium, Serum (Mass Concentration)

Published: August 9, 2026Updated: August 15, 2026

This test measures the amount of calcium in your blood serum, which is important for maintaining healthy bones, muscles, nerves, and other body functions.

Quick summary

["Your blood calcium levels help ensure strong bones and proper nerve/muscle function."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 15, 2026Editorial policy

Key facts at a glance

LOINC
16504-3
Short code
CT-POST
Synonyms
Calcit 1.5M p chal SerPl-mCnc
Category
chemistry
Sample
serum
Container
Serum separator tube (SST) or red-top tube without anticoagulant for serum; heparinized plasma tube acceptable for plasma specimens
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 18 years
Method
Immunoassay (Chemiluminescent or Radioimmunoassay)
CPT
82308
SNOMED
104126001
Specimen volume
1-2 mL of serum or plasma
Stability
Room temperature: 2 hours; Refrigerated (2-8°C): 24 hours; Frozen (-20°C or below): 1 month. For extended storage, freeze at -70°C or lower.
Hemolysis max
100
Lipemia max
100
Icterus max
50
TAT
24–72 hours
Order
routine

Why Is This Test Done?

Doctors may order a serum calcium test to check for conditions like low or high calcium levels, which can affect bones, muscles, or heart function. It’s often done if you have symptoms like muscle spasms, fatigue, or kidney issues, or if you have conditions like osteoporosis, kidney disease, or thyroid problems.

What to Expect Before the Test

You’ll typically have a small needle inserted into a vein in your arm. The blood sample is taken, and you may feel a slight pinch. No special preparation is needed unless your doctor instructs otherwise.

What the Results Mean

Results help doctors diagnose or monitor conditions like hypocalcemia (low calcium) or hypercalcemia (high calcium). While reference ranges vary by lab, abnormal results may signal underlying health concerns that need further evaluation.

Common Conditions Linked to Abnormal Results

Low calcium levels might be linked to conditions like vitamin D deficiency, kidney problems, or certain medications. High levels could be due to overactive thyroid, cancer, or prolonged bed rest.

Reference range

Reference ranges for post-stimulation calcitonin are test-specific and dependent on the stimulating agent, dose, and patient population. Peak calcitonin values following calcium or pentagastrin stimulation are interpreted in the context of basal calcitonin levels. Generally, a peak calcitonin level >100 pg/mL is suggestive of medullary thyroid carcinoma (MTC). Consult laboratory-specific reference ranges and clinical guidelines for interpretation.N/A

Specimen: serum

Fasting is not required. However, patients should avoid biotin supplements for at least 24-48 hours prior to testing as biotin may interfere with immunoassay results. Patients should be informed about the stimulation procedure and any potential side effects associated with the challenging agent (calcium gluconate or pentagastrin).

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Serum calcium levels are critical for bone health, nerve signaling, and muscle function. Abnormal results may indicate conditions affecting these systems, prompting further medical evaluation to identify the cause and guide treatment.

Short name

Serum Calcium Level

Frequently asked questions

What causes my calcium levels to be checked regularly?
Your doctor may recommend regular calcium tests if you have conditions like osteoporosis, kidney disease, thyroid disorders, or if you take medications that affect calcium levels. It’s also done during pregnancy or if you have symptoms like muscle cramps or bone pain.
How long does it take to get my test results?
Results are usually available within 1–3 business days, depending on your lab and insurance. Your doctor will contact you with the findings once they’re ready.
Can diet or supplements affect my calcium test results?
Yes, high intake of calcium-rich foods or supplements (like dairy or vitamin D) before the test may temporarily alter results. Avoid large doses of calcium or vitamin D 24–48 hours before testing unless advised otherwise.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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 15, 2026. · Read our editorial policy