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Calcium in Serum (Mass Concentration)

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

This test measures the amount of calcium present in your blood serum. Calcium is an essential mineral that helps maintain strong bones, supports nerve and muscle function, and aids in blood clotting.

Quick summary

["Your serum calcium level helps doctors assess bone health, kidney function, and overall mineral balance in your body."]

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

Key facts at a glance

LOINC
33787-3
Short code
CALC10
Synonyms
Calcit sp10 p chal SerPl-mCnc
Category
chemistry
Sample
serum
Container
Serum separator tube (SST) or red-top clot tube; plasma acceptable in lithium-heparin or EDTA tube
Units
N/A
Ref low
0
Ref high
10
Critical range
— – 1000 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–99 years
Method
Immunoassay (Chemiluminescent Immunoassay [CLIA] or Radioimmunoassay [RIA])
CPT
82308
SNOMED
395240008
Specimen volume
1.0 mL serum or plasma
Stability
Room temperature: 2 hours; Refrigerated (2-8°C): 24 hours; Frozen (-20°C or below): 30 days. Avoid repeated freeze-thaw cycles.
Hemolysis max
100
Lipemia max
300
Icterus max
25
TAT
24–72 hours
Order
routine

Why This Test Is Done

Doctors may order a serum calcium test to check for conditions like low or high calcium levels, which can cause symptoms such as muscle cramps, fatigue, or irregular heartbeats. It’s also used to monitor kidney disease, bone disorders, or metabolic issues.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a broader metabolic panel. Bring any medications you’re taking, as some (like calcium supplements or certain diuretics) can affect results.

What the Results Mean

Results are typically reported in milligrams per deciliter (mg/dL). While reference ranges vary by lab, low levels may indicate conditions like hypoparathyroidism or kidney problems, while high levels could signal hypercalcemia or overuse of vitamin D.

Possible Causes of Abnormal Results

Changes in calcium levels can stem from dietary factors (e.g., excess dairy or vitamin D), medical conditions (e.g., cancer, thyroid disorders), or medications. Your doctor will discuss findings in the context of your full health picture.

Reference range

Reference ranges for calcitonin stimulation testing (e.g., pentagastrin or calcium challenge) are laboratory- and assay-specific; basal calcitonin <10 pg/mL (males) and <5 pg/mL (females) are commonly cited upper limits, with stimulated peak values interpreted relative to baseline (e.g., >100 pg/mL suggestive of medullary thyroid carcinoma). Consult reporting laboratory for 10th post-challenge specimen-specific reference values.N/A

Specimen: serum

No special fasting required. Patient should be informed about the stimulation procedure (pentagastrin, calcium gluconate, or omeprazole challenge). Discontinue biotin supplements at least 72 hours prior to testing if using streptavidin-biotin-based assays.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Serum Calcium Level

Frequently asked questions

Could my calcium levels be affected by my diet?
Yes, dietary calcium (from foods like dairy, leafy greens, or fortified foods) and vitamin D (from sunlight or supplements) play a key role. However, your doctor will consider other factors like kidney function or medications when interpreting results.
What symptoms might indicate a calcium imbalance?
Symptoms of low calcium may include muscle spasms, numbness, or frequent bone fractures. High calcium levels might cause nausea, confusion, or kidney stones. Always discuss symptoms with your doctor, as they can vary widely.
How often should I get this test?
Your doctor will determine frequency based on your health needs—such as routine check-ups, monitoring chronic conditions, or symptoms. Regular tests may be recommended if you have conditions like osteoporosis, kidney disease, or thyroid disorders.
  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