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Calcium, Serum or Plasma Concentration (Mass)

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

This test measures the amount of calcium in your blood, which is important for many body functions, including muscle and nerve function, as well as bone health.

Quick summary

["Your calcium levels help ensure your body stays strong and functions properly."]

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

Key facts at a glance

LOINC
77668-2
Short code
CALC5
Synonyms
Calcit 5M p chal SerPl-sCnc
Category
chemistry
Sample
serum
Container
Red-top serum tube or serum separator tube (SST)
Units
N/A
Ref low
0
Ref high
100
Fasting
false
Population
adult
Sex
all
Age range
≥ 18 years
Method
Immunoassay (Chemiluminescent or Radioimmunoassay)
CPT
82308
SNOMED
39579003
Specimen volume
1-2 mL serum
Stability
Serum stable for 8 hours at room temperature; 24 hours refrigerated at 2-8°C; frozen at -20°C for up to 30 days for prolonged storage
Hemolysis max
100
Lipemia max
200
Icterus max
40
TAT
24–72 hours
Order
routine

Why Is This Test Done?

Doctors may order this test to check for conditions like low or high calcium levels, which can cause symptoms such as muscle cramps, weakness, or irregular heartbeats. It may also be used to monitor conditions like kidney disease, osteoporosis, or certain hormonal imbalances.

What Does It Measure?

This test measures the total calcium present in your blood, including both ionized (active) and protein-bound calcium. Ionized calcium is the form that directly affects nerve and muscle function.

Sample Collection and Preparation

A blood sample is typically taken from a vein in your arm. The blood is collected in a special tube that prevents clotting and separates serum or plasma from blood cells. This sample is then sent to a lab for analysis.

What to Expect Before the Test

There are usually no special preparations needed for this test. However, if you are on certain medications that affect calcium levels, your doctor may ask you to stop them temporarily or adjust your dosage.

Reference range

Reference ranges vary by laboratory and assay method; post-stimulation values are interpreted relative to baseline and stimulation type. Peak calcitonin response to pentagastrin stimulation in adults is generally <100 pg/mL; values >100 pg/mL suggest medullary thyroid carcinoma (MTC). For calcium stimulation, peak values are similarly interpreted in clinical context.N/A

Specimen: serum

No special preparation required. Patient should be in fasting state if possible. Stimulation challenge (pentagastrin, calcium gluconate, or other secretagogues) must be administered per established protocol, with blood drawn exactly 5 minutes post-challenge.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Calcium Level

Frequently asked questions

Low calcium levels (hypocalcemia) can cause muscle spasms, numbness, or seizures, while high levels (hypercalcemia) may lead to fatigue, confusion, or kidney stones. Chronic imbalances can affect bone health and heart function.
What does a low calcium level mean? A low calcium level might indicate conditions such as vitamin D deficiency, kidney problems, or certain hormonal disorders. It can also be caused by medications or dietary factors.
What does a high calcium level mean? A high calcium level may suggest overactive thyroid, cancer, or prolonged exposure to certain medications. It can also be linked to conditions like hyperparathyroidism.
How often should I get this test? Your doctor will determine the frequency based on your health status, symptoms, and any ongoing conditions. Regular monitoring may be recommended if you have chronic diseases like kidney disease or osteoporosis.
Can I eat or drink anything before the test? You can usually eat and drink normally before this test unless instructed otherwise by your healthcare provider.
Is there any risk or discomfort with this test? Blood tests are generally safe and well-tolerated. You might feel a slight pinch when the needle is inserted, but most people experience minimal discomfort.
  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