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Calcium (Serum) - Mass Concentration

Published: August 9, 2026Updated: August 14, 2026

This test measures the amount of calcium in your blood serum, an important mineral that helps your body function properly, including muscle and nerve activity.

Quick summary

["Your blood calcium levels help maintain strong bones, healthy nerves, and proper muscle function."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 14, 2026Editorial policy

Key facts at a glance

LOINC
50476-1
Short code
CALC8
Synonyms
Calcit sp8 SerPl-mCnc
Category
chemistry
Sample
serum
Container
Serum separator tube (SST) or red-top tube without anticoagulant for serum; heparinized plasma tube (green-top) acceptable for plasma specimen
Units
N/A
Ref low
0
Ref high
10
Critical range
— – 100 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
Immunoassay (Chemiluminescent)
CPT
82308
SNOMED
39579001
Specimen volume
1.0 mL serum or plasma; minimum 0.5 mL required
Stability
Room temperature: 2 hours; Refrigerated (2-8°C): 24 hours; Frozen (-20°C or below): 3 months. Avoid repeated freeze-thaw cycles.
Hemolysis max
100
Lipemia max
200
Icterus max
40
TAT
24–72 hours
Order
routine

Why This Test Is Done

Doctors may order a calcium test to check for conditions like low or high calcium levels, which can cause symptoms such as muscle cramps, bone pain, or irregular heart rhythms. It may also be done to monitor certain treatments or medical conditions, such as kidney disease or osteoporosis.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if it involves a fasting sample, but this is not always required for a simple serum calcium test. Wear comfortable clothing and bring any medications you’re currently taking.

During the Test

A healthcare professional will draw blood from a vein, usually in your arm. You may feel a slight pinch, but the process is quick and typically painless. The blood sample is then sent to a lab for testing.

What the Results Mean

Results are reported in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). While reference ranges vary slightly by lab, low levels may suggest conditions like hypoparathyroidism or vitamin D deficiency, while high levels could indicate kidney problems or overactive thyroid.

Reference range

Reference ranges vary by assay methodology, age, and sex. Generally, basal calcitonin levels are <10 pg/mL (or <2.0 ng/L) in adult males and <5 pg/mL (or <1.0 ng/L) in adult females. Values for the 8th specimen in dynamic testing should be interpreted against baseline and expected stimulation response curves.N/A

Specimen: serum

No special patient preparation required for basal measurement. For stimulation testing (pentagastrin or calcium infusion), patients should fast for at least 8 hours prior to the procedure and remain supine during the test. Discontinue biotin supplements 72 hours before specimen collection as they may interfere with immunoassay results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Calcium Level

Frequently asked questions

What Are Common Causes of Low Calcium?
Low calcium levels (hypocalcemia) can result from conditions like vitamin D deficiency, kidney disease, or certain medications. Symptoms may include muscle spasms, numbness, or an irregular heartbeat. If you experience these, discuss them with your doctor.
What Are Common Causes of High Calcium?
High calcium levels (hypercalcemia) may occur due to overactive thyroid, kidney issues, or certain cancers. Symptoms can include fatigue, nausea, or frequent urination. Your doctor may recommend further testing if results are elevated.
How Often Should I Get This Test?
The frequency depends on your health status. If you have a chronic condition like kidney disease or osteoporosis, your doctor may schedule regular tests. Otherwise, this test is often done only when symptoms or risk factors suggest it’s needed.
  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 14, 2026. · Read our editorial policy