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 12926-2: T4 5th specimen post Unsp challenge [Mass/Vol]

Name: LOINC Code 12926-2: T4 5th specimen post Unsp challenge [Mass/Vol]
Creator: HealthAssure Clinical Team
Published: 2026-05-21T11:17:23.607Z

12926-2 is a LOINC code used to identify T4 5th specimen post Unsp challenge [Mass/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 Thyroxine^5th 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 Thyroxine^5th 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

Thyroxine (T4) [Mass/volume] in Serum or Plasma --5th specimen post XXX challenge
Thyroxine^5th specimen post XXX challenge
After; CHEMISTRY.CHALLENGE TESTING; Endocrine; Endocrinology; Level; Levothyroxine; Levo-thyroxine; L-thyroxine; Mass concentration; p chal; Pl; Plasma; Plsm; Point in time; PST; QNT; Quan; Quant; Quantitative; Random; SerP; SerPl; SerPlas; Serum; Serum or plasma; sp5; sp5 p chal; Spec; SR; T4; T-4; thyroid hormone; Thyrox; Thyroxin; Thyrx; Total T4; TT4

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

T4 5th specimen post Unsp challenge [Mass/Vol]Thyroxine (T4) [Mass/volume] in Serum or Plasma --5th specimen post XXX challengeT4 sp5 p chal SerPl-mCncThyroxine^5th specimen post XXX challengeCHALT4 5th specimen after challenge, BloodMCnc

Frequently asked questions

Code details

Code12926-2

SystemLOINC

Display nameT4 5th specimen post Unsp challenge [Mass/Vol]

DescriptionThyroxine^5th specimen post XXX challenge

Short nameT4 sp5 p chal SerPl-mCnc

ComponentThyroxine^5th specimen post XXX challenge

PropertyMCnc

TimingPt

System (specimen)Ser/Plas

ScaleQn

ClassCHAL

Example unitsug/dL

StatusACTIVE

Order/ObservationObservation

Flags

BillableNo

Valid clinical useNo

Source

SourceLOINC

Version2.82

Releasemain

First released1.0j-a

Last changed2.40

Consumer names

T4 5th specimen after challenge, Blood

Part names

Thyroxine^5th specimen post XXX challengeMCncPtSer/PlasQnMass 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.