Calcium Ion Concentration (Serum/Plasma)
This test measures the amount of free, unbound calcium in your blood, which is important for muscle function, nerve signaling, and bone health.
["Understanding your free calcium levels helps assess bone health and electrolyte balance."]
Key facts at a glance
- LOINC
- 57338-6
- Short code
- Citrate 2h Ur-mCnc
- Synonyms
- Citrate 2h Ur-mCnc
- Category
- chemistry
- Sample
- urine
- Container
- Sterile urine container
- Units
- N/A
- Ref low
- 20
- Ref high
- 400
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82670
- Specimen volume
- 10 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your doctor may order this test if you have symptoms like muscle cramps, irregular heartbeat, or signs of low or high calcium levels. It’s also checked during conditions like kidney disease, osteoporosis, or certain metabolic disorders.
What Does the Result Mean?
Free calcium levels can vary based on other blood components and binding proteins. While reference ranges differ by lab, very low levels may indicate conditions like hypoparathyroidism, while very high levels could suggest hypercalcemia or certain cancers.
How Is This Test Performed?
A blood sample is drawn from a vein, usually in your arm. The serum or plasma is then analyzed to measure free calcium concentration using a specialized laboratory method.
What Are Common Causes of Abnormal Results?
Changes in free calcium can stem from dietary intake, kidney function, hormone imbalances (like vitamin D or parathyroid hormone), or certain medications.
Reference range
Premenopausal: 20-400 pg/mL; Postmenopausal: <30 pg/mLN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free calcium is critical for normal physiological functions, including nerve and muscle activity. Abnormal levels can lead to complications like arrhythmias, muscle spasms, or weakened bones. Regular monitoring may be needed if you have chronic conditions affecting calcium metabolism.
Short name
Serum Calcium Ion Level
Frequently asked questions
Why might my doctor ask for this test repeatedly?
What should I do if my calcium ion levels are out of range?
Can diet affect this test result?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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 16, 2026. · Read our editorial policy