Calcium, Serum/Plasma
A blood test that measures the total amount of calcium in your blood and helps assess calcium balance and conditions affecting bone, muscle, and nerve function.
["This test checks the calcium level in your blood; your clinician will interpret it along with your medical history and other laboratory results."]
Key facts at a glance
- LOINC
- 61512-0
- Short code
- Calcium PhenX
- Synonyms
- Calcium PhenX
- Category
- liver
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 8.5
- Ref high
- 10.5
- Critical range
- 6 N/A – 14 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- phenx
- CPT
- 82310
- SNOMED
- 110744001
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What is this test?
This test measures the amount of calcium in a blood sample. Most calcium in the body is stored in bones and teeth, while the remainder circulates in the blood and helps support muscle contraction, nerve signaling, and heart function.
Why might I need this test?
Your clinician may order this test to evaluate symptoms that can be related to abnormal calcium levels, such as muscle cramps, weakness, tingling, confusion, or changes in heart rhythm. It may also be used to monitor certain medicines, kidney conditions, bone disorders, or parathyroid gland problems.
How is the test performed?
A healthcare professional draws a small amount of blood from a vein, usually in your arm. The sample is sent to a laboratory, where the calcium level is measured and reported.
How do I prepare for the test?
This blood test usually requires no special preparation. Follow your clinician's instructions, and tell the laboratory if you are pregnant or taking medicines or vitamin or mineral supplements that may affect calcium levels.
Reference range
Adult: 8.5-10.5 mg/dLN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
A calcium level above the expected range may occur with conditions affecting the parathyroid glands, excess vitamin D, some kidney problems, or the use of certain medicines. A level below the expected range may occur with low parathyroid hormone, vitamin D deficiency, kidney disease, or inadequate calcium intake. Your clinician will interpret the result using your symptoms, medical history, and other tests.
Short name
Calcium
Frequently asked questions
Does this test show how much calcium is in my bones?
Is fasting required for a calcium blood test?
Can calcium supplements or antacids affect the 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