What does this LOINC code represent?

This LOINC code identifies a lab observation, measurement, question, or clinical concept in a standardized format.

Is this enough to understand my test result?

No. The code identifies the test or observation, but the interpretation depends on the actual result, reference range, and clinical context.

LOINCActiveObservation

LOINC Code 16516-7: Calcium.ionized 6th specimen post Unsp challenge [Moles/Vol]

Name: LOINC Code 16516-7: Calcium.ionized 6th specimen post Unsp challenge [Moles/Vol]
Creator: HealthAssure Clinical Team
Published: 2026-05-21T11:17:26.378Z

16516-7 is a LOINC code used to identify Calcium.ionized 6th specimen post Unsp challenge [Moles/Vol] in laboratory and clinical observation data. You may see this code in lab systems, lab reports, EHR exports, interoperability feeds, or other structured clinical data exchanges. LOINC codes identify tests, measurements, observations, survey items, and clinical questions in a standardized way. It is associated with the component Calcium.ionized^6th specimen post XXX challenge. It is commonly used with the system or sample type Ser/Plas.

Reviewed by HealthAssure Clinical TeamUpdated 21 May 2026

What is this code?

LOINC codes identify tests, measurements, observations, survey items, and clinical questions in a standardized way. It is associated with the component Calcium.ionized^6th specimen post XXX challenge. It is commonly used with the system or sample type Ser/Plas.

When is it used?

Used in lab systems, EHRs, and clinical data exchange.
May identify a test, observation, survey item, or clinical document request rather than a diagnosis.
Status: ACTIVE
Order vs observation: Observation

What it does not mean

The code identifies the observation or test, not the actual result.

Key facts

Calcium.ionized [Moles/volume] in Serum or Plasma --6th specimen post XXX challenge
Calcium.ionized^6th specimen post XXX challenge
After; Ca; Ca-I; Cal; Calcium active; Calcium free; CHEMISTRY.CHALLENGE TESTING; Coagulation factor I; ICA; Ion; Level; p chal; Pl; Plasma; Plsm; Point in time; PST; QNT; Quan; Quant; Quantitative; Random; SerP; SerPl; SerPlas; Serum; Serum or plasma; sp6; sp6 p chal; Spec; SR; Substance concentration

Where you may see this code

You may see this code in lab systems, lab reports, EHR exports, interoperability feeds, or other structured clinical data exchanges.

Common synonyms

Calcium.ionized 6th specimen post Unsp challenge [Moles/Vol]Calcium.ionized [Moles/volume] in Serum or Plasma --6th specimen post XXX challengeCa-I sp6 p chal SerPl-sCncCalcium.ionized^6th specimen post XXX challengeCHALCalcium.ionized 6th specimen after challenge, BloodSCnc

Frequently asked questions

Code details

Code16516-7

SystemLOINC

Display nameCalcium.ionized 6th specimen post Unsp challenge [Moles/Vol]

DescriptionCalcium.ionized^6th specimen post XXX challenge

Short nameCa-I sp6 p chal SerPl-sCnc

ComponentCalcium.ionized^6th specimen post XXX challenge

PropertySCnc

TimingPt

System (specimen)Ser/Plas

ScaleQn

ClassCHAL

Example unitsmmol/L

StatusACTIVE

Order/ObservationObservation

Flags

BillableNo

Valid clinical useNo

Source

SourceLOINC

Version2.82

Releasemain

First released1.0l

Last changed2.34

Consumer names

Calcium.ionized 6th specimen after challenge, Blood

Part names

Calcium.ionized^6th specimen post XXX challengeSCncPtSer/PlasQnSubstance ConcentrationPoint in time (spot)Serum or Plasma

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from LOINC. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.