Can this result diagnose a condition on its own?

No. Laboratory results are interpreted with symptoms, medical history, specimen conditions and related tests.

Which reference range should I use?

Start with the performing laboratory's own reference interval; clinical cutoffs, when relevant, are separate sourced thresholds used for a specific purpose.

When should I discuss the result with a healthcare professional?

Results that are clearly outside range, persistent, symptomatic or unexpected should be reviewed by a healthcare professional.

Information about a laboratory test

Low Ionized Calcium: What Does It Mean?

A low result can occur with kidney, hormonal, nutritional, absorption or medication-related factors; related minerals and clinical context matter.

Test summary

Test name: Ionized Calcium
Abbreviations: iCa, Free calcium
Category: Minerals / Calcium Metabolism
Panel: Bone & Mineral Metabolism
Specimen: Whole blood / serum / plasma
Common units: mg/dL, mmol/L

What does the test measure?

The Ionized Calcium test measures the biologically active calcium that is not bound to proteins.

Why is the test ordered?

Ordered with related tests to assess mineral balance, kidney/endocrine regulation or bone metabolism.

Information about a low result

A low result can occur with kidney, hormonal, nutritional, absorption or medication-related factors; related minerals and clinical context matter.

Information about a high result

A high result can occur with kidney, hormonal, supplement/medicine or other mineral-balance factors; related tests provide context.

Reference and clinical context

Start with the performing laboratory's reference interval, unit, specimen type and method. Numeric information on this page is stored as sourced example intervals or clinical thresholds.

Reference range 1

>= 4.8 – <= 5.6 mg/dL

Population: Adults
Age range: 18
Specimen: Whole blood / serum / plasma

Sourced example reference interval for Ionized Calcium

This is a sourced example reference interval; laboratory, method, age and clinical context can change the range. The user's own report takes priority.

Reference range 2

>= 4.8 – <= 5.3 mg/dL

Population: Children
Age range: 0 – 17
Specimen: Whole blood / serum / plasma

Sourced example reference interval for Ionized Calcium

This is a sourced example reference interval; laboratory, method, age and clinical context can change the range. The user's own report takes priority.

Reference ranges may vary by laboratory, method used, age, sex, pregnancy status, and clinical context. The reference range on your own laboratory report takes precedence.

Interpretation notes

A single mineral value is often insufficient; PTH, vitamin D, kidney function and related minerals may need to be interpreted together.

Related specialties

Endocrinology
Internal Medicine
Nephrology
Family Medicine

Frequently asked questions

Sources

Calcium Blood Test — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2025 · Total calcium purpose, albumin context and example adult reference interval · Verified: Aug 12, 2026
Calcium – Ionized — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2025 · Ionized calcium role and adult/pediatric example reference intervals · Verified: Aug 12, 2026