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 58840-0: Free T3 baseline [Mass/Vol]

Name: LOINC Code 58840-0: Free T3 baseline [Mass/Vol]
Creator: HealthAssure Clinical Team
Published: 2026-05-21T08:59:39.276Z

58840-0 is a LOINC code used to identify Free T3 baseline [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 Triiodothyronine.free^baseline. 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 Triiodothyronine.free^baseline. 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

Triiodothyronine (T3) Free [Mass/volume] in Serum or Plasma --baseline
Triiodothyronine.free^baseline
BS; CHEMISTRY.CHALLENGE TESTING; Endocrine; Endocrinology; FR; Free T3; FT3; Level; Mass concentration; Non-protein bound; Pl; Plasma; Plsm; Point in time; QNT; Quan; Quant; Quantitative; Random; SerP; SerPl; SerPlas; Serum; Serum or plasma; SR; T3; T-3; T3Free; thyroid hormone; Total T3; Triodothyrne

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

Free T3 baseline [Mass/Vol]Triiodothyronine (T3) Free [Mass/volume] in Serum or Plasma --baselineT3Free BS SerPl-mCncTriiodothyronine.free^baselineCHALFree T3 baseline, BloodMCnc

Frequently asked questions

Code details

Code58840-0

SystemLOINC

Display nameFree T3 baseline [Mass/Vol]

DescriptionTriiodothyronine.free^baseline

Short nameT3Free BS SerPl-mCnc

ComponentTriiodothyronine.free^baseline

PropertyMCnc

TimingPt

System (specimen)Ser/Plas

ScaleQn

ClassCHAL

Example unitspg/mL

StatusACTIVE

Order/ObservationObservation

Flags

BillableNo

Valid clinical useNo

Source

SourceLOINC

Version2.82

Releasemain

First released2.32

Last changed2.70

Consumer names

Free T3 baseline, Blood

Part names

Triiodothyronine.free^baselineMCncPtSer/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.