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 27987-7: Free T4 baseline Qn

Name: LOINC Code 27987-7: Free T4 baseline Qn
Creator: HealthAssure Clinical Team
Published: 2026-05-21T08:59:14.572Z

27987-7 is a LOINC code used to identify Free T4 baseline Qn 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.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 Thyroxine.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

Thyroxine (T4) free [Units/volume] in Serum or Plasma --baseline
Thyroxine.free^baseline
Arbitrary concentration; BS; CHEMISTRY.CHALLENGE TESTING; Endocrine; Endocrinology; FR; FreeT4; FT4; Levothyroxine; Levo-thyroxine; L-thyroxine; Non-protein bound; Pl; Plasma; Plsm; Point in time; QNT; Quan; Quant; Quantitative; Random; SerP; SerPl; SerPlas; Serum; Serum or plasma; SR; T4; T-4; T4 Free; 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

Free T4 baseline QnThyroxine (T4) free [Units/volume] in Serum or Plasma --baselineT4 Free BS SerPl-aCncThyroxine.free^baselineCHALFree T4 baseline, BloodACnc

Frequently asked questions

Code details

Code27987-7

SystemLOINC

Display nameFree T4 baseline Qn

DescriptionThyroxine.free^baseline

Short nameT4 Free BS SerPl-aCnc

ComponentThyroxine.free^baseline

PropertyACnc

TimingPt

System (specimen)Ser/Plas

ScaleQn

ClassCHAL

Example unitsmIU/L

StatusACTIVE

Order/ObservationObservation

Flags

BillableNo

Valid clinical useNo

Source

SourceLOINC

Version2.82

Releasemain

First released2.00

Last changed2.42

Consumer names

Free T4 baseline, Blood

Part names

Thyroxine.free^baselineACncPtSer/PlasQnArbitrary 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.