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Calcium, Serum

Published: August 9, 2026Updated: August 17, 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 and support vital bodily processes."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
77669-0
Short code
CALC30
Synonyms
Calcit 30M p chal SerPl-sCnc
Category
chemistry
Sample
serum
Container
Red-top serum tube (no anticoagulant) or serum separator tube (SST)
Units
N/A
Ref low
0
Ref high
10
Critical range
20 N/A – 400 N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 18 years
Method
Chemiluminescent Immunoassay (CLIA) or Electrochemiluminescence Immunoassay (ECLIA)
CPT
82308
SNOMED
39572002
Specimen volume
1.0 mL of serum minimum (3.0 mL recommended for stimulation studies with multiple draws)
Stability
Serum calcitonin is stable for 8 hours at room temperature (15-25°C), 24 hours at 2-8°C, and up to 3 months at -20°C or below. For prolonged storage, -70°C is recommended. Avoid repeated freeze-thaw cycles.
Hemolysis max
100
Lipemia max
200
Icterus max
25
TAT
24–72 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order a serum calcium test to check for conditions affecting bone health, kidney function, or hormone imbalances. It can also help diagnose or monitor diseases like osteoporosis, hyperparathyroidism, or kidney disorders.

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’s part of a metabolic panel, but this isn’t always required. Bring any medications you’re currently taking to your appointment.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm using a small needle. You may feel a slight pinch, but it usually doesn’t cause discomfort. The blood sample is then sent to a lab for analysis.

What Are Possible Results?

Results are typically reported in milligrams per deciliter (mg/dL). Your provider will interpret the results in relation to your overall health and medical history.

Reference range

Reference values vary by laboratory, assay method, and patient sex. Basal calcitonin levels are typically <10 pg/mL (equivalent to <2.9 pmol/L) in adult females and <15 pg/mL (<4.4 pmol/L) in adult males when measured by immunoassay. Peak stimulated calcitonin values depend on the provocative agent used (e.g., calcium or pentagastrin). Generally, stimulated calcitonin values are interpreted relative to basal values; a stimulated peak exceeding 100 pg/mL in females or 200 pg/mL in males is suggestive of medullary thyroid carcinoma (MTC). Please refer to the performing laboratory's reference range.N/A

Specimen: serum

No special preparation required. However, the patient should be in a rested state for at least 30 minutes prior to and during the provocative challenge test. Inform the physician of all medications, particularly those affecting calcium homeostasis. The provocative agent (calcium gluconate or pentagastrin) is administered as part of a standardized stimulation protocol.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Serum calcium levels play a critical role in preventing bone loss, regulating muscle contractions, and maintaining nerve function. Abnormally low or high levels can lead to symptoms like muscle cramps, fatigue, or even heart problems. Chronic imbalances may indicate underlying conditions like vitamin D deficiency, kidney disease, or thyroid disorders.

Short name

Serum Calcium

Frequently asked questions

What does a low serum calcium level mean?
A low calcium level (hypocalcemia) may cause muscle spasms, numbness, or irregular heartbeat. It can also lead to conditions like tetany, where muscles twitch uncontrollably. Causes may include kidney problems, vitamin D deficiency, or certain medications.
What does a high serum calcium level mean?
High calcium levels (hypercalcemia) can cause fatigue, kidney stones, or frequent urination. It may result from overactive thyroid, bone diseases, or prolonged exposure to certain medications. Your provider will assess symptoms and lab results to determine the cause.
Can diet affect serum calcium test results?
Yes, diet can influence calcium levels. Consuming high amounts of calcium-rich foods (like dairy, leafy greens) or calcium supplements may temporarily alter results. Avoiding calcium supplements for a few days before the test can help ensure accurate results.
  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 17, 2026. · Read our editorial policy