Blood Calcium Test (Serum Calcium)
A blood test that measures the level of calcium in your bloodstream to help your doctor evaluate the health of your bones, how well your kidneys are working, and whether your parathyroid glands are functioning properly. Calcium is an essential mineral that also supports healthy nerve signaling, muscle movement, and normal blood clotting.
{"Calcium is an essential mineral for strong bones, nerve signaling, and muscle contraction","This test is often part of a routine metabolic panel or comprehensive metabolic panel","Abnormal calcium levels may indicate kidney disease, parathyroid disorders, or vitamin D deficiency","The test requires a simple blood draw from a vein in your arm","No special preparation is usually needed, though your doctor may ask you to fast"}
Key facts at a glance
- LOINC
- 27182-5
- Short code
- Ca
- Synonyms
- Calcium Bld Ql
- Category
- electrolyte
- Sample
- whole-blood
- Container
- Serum separator tube (SST/gel tube) or plain red top tube for total calcium; heparinized whole blood or plasma for ionized calcium measurement
- Units
- not specified
- Ref low
- 8.5
- Ref high
- 10.5
- Critical range
- 7 not specified – 13 not specified
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Colorimetric assay using arsenazo III dye or o-cresolphthalein complexone (OCPC) method; Ion-selective electrode (ISE) for ionized calcium measurement
- CPT
- 82310
- SNOMED
- 271082005
- Specimen volume
- 2-3 mL serum or plasma; 1-2 mL for point-of-care testing
- Stability
- Room temperature: 7 days; Refrigerated (2-8°C): 7-14 days; Frozen (-20°C): several months. Ionized calcium stability: 24-48 hours at room temperature in sealed container.
- Hemolysis max
- 50
- Lipemia max
- 100
- Icterus max
- 2
- TAT
- 1–4 hours
- Order
- routine
What is this test?
The Blood Calcium Test measures the concentration of calcium in your blood. Calcium is a vital mineral that plays a crucial role in maintaining strong bones and teeth, supporting nerve function, enabling muscle contraction, and helping blood clot properly. This test detects both the calcium bound to proteins (bound calcium) and the free, active calcium (ionized calcium) in your bloodstream.
Why is it important?
Calcium levels are carefully regulated by your body through the parathyroid hormone (PTH), vitamin D, and kidney function. When these systems are out of balance, calcium levels can become too high (hypercalcemia) or too low (hypocalcemia). Either condition can lead to serious health problems, including heart rhythm abnormalities, muscle weakness, confusion, and bone loss.
How is the test performed?
A healthcare professional will draw a small sample of blood from a vein in your arm using a needle. The blood sample is then sent to a laboratory for analysis. The procedure only takes a few minutes and is generally well-tolerated. You may experience slight bruising or soreness at the puncture site afterward.
When is it ordered?
This test is commonly ordered as part of a routine health checkup or metabolic panel. Your doctor may also request it if you have symptoms of calcium imbalance (such as fatigue, muscle cramps, weakness, or irregular heartbeat), kidney disease, bone disorders, or parathyroid problems. It may also be monitored if you are taking calcium or vitamin D supplements.
Reference range
Negativenot specified
No special preparation or fasting required
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated calcium levels (hypercalcemia) may indicate hyperparathyroidism, certain cancers, vitamin D toxicity, kidney disease, or overuse of calcium supplements. Symptoms include excessive thirst, frequent urination, nausea, fatigue, and confusion.
Low calcium levels (hypocalcemia) may result from hypoparathyroidism, vitamin D deficiency, kidney failure, pancreatitis, or certain medications. Symptoms include muscle twitching, seizures, tingling in the lips and fingers, and dry skin.
Your doctor will interpret your results based on your overall health, symptoms, and other test findings. Abnormal results often require additional testing to determine the underlying cause.
Frequently asked questions
Do I need to fast before the test?
Are there any risks with this test?
What do high calcium levels mean?
What do low calcium levels mean?
Can I take my regular medications before the test?
Sources
- 1
- 2
- 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 10, 2026. · Read our editorial policy