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Calcium, Total, Blood — Concentration

Published: August 9, 2026Updated: August 16, 2026

A blood test that measures total calcium, including the calcium bound to proteins and the small amount that is free.

Quick summary

["Total calcium helps assess calcium balance and may be affected by bone, kidney, vitamin D, or parathyroid problems."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
88318-1
Short code
CTA CA+PV W contr IV
Synonyms
CTA CA+PV W contr IV
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ct-angio
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?

A total calcium test measures the overall amount of calcium in a blood sample. Most calcium is bound to proteins, while a small portion is free and active in the body.

Why might I need this test?

Your clinician may order this test as part of a general health assessment or to evaluate problems involving bones, kidneys, vitamin D, or the parathyroid glands. It may also be monitored when taking certain medicines or supplements that affect calcium.

How is the test performed?

A blood sample is collected and analyzed in the laboratory. The exact specimen type and laboratory method may vary, and the sample is usually obtained with a routine blood draw or finger-stick collection.

How do I prepare for the test?

Special preparation is usually not required. Follow any instructions from your clinician, and tell the laboratory if you take calcium or vitamin D supplements or medicines that may affect calcium levels.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Total calcium

Frequently asked questions

What does a total calcium test measure?
It measures the total calcium in blood, including calcium attached to proteins and the smaller free, or ionized, portion.
What can cause an abnormal calcium result?
Abnormal results may occur with parathyroid, kidney, bone, or vitamin D disorders. Medicines, calcium supplements, protein levels, and hydration can also affect the result.
Do I need to stop taking supplements before the test?
Do not stop prescribed medicines or supplements unless your clinician instructs you to do so. Tell the healthcare team about calcium and vitamin D supplements so the result can be interpreted appropriately.
  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 16, 2026. · Read our editorial policy