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 90804-6: Levothyroxine absorption Calc [Mass fraction]

Name: LOINC Code 90804-6: Levothyroxine absorption Calc [Mass fraction]
Creator: HealthAssure Clinical Team
Published: 2026-05-21T09:00:20.875Z

90804-6 is a LOINC code used to identify Levothyroxine absorption Calc [Mass fraction] 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 Levothyroxine absorption. 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 Levothyroxine absorption. 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
Method: Calculated

What it does not mean

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

Key facts

Levothyroxine absorption in Serum or Plasma by calculation

Levothyroxine absorption

The percent absorption of levothyroxine, as determined based on the incremental increase in Ser/Plas thyroxine [LOINC90803-8], the volume of distribution [LOINC: 90802-0], and the dose of levothyroxine that was administered [LOINC: 18615-5]

Absorp; c99; Calc; Calculation; CHEMISTRY.CHALLENGE TESTING; L-thyroxine; Mass fraction; Percent; Pl; Plasma; Plsm; Point in time; QNT; Quan; Quant; Quantitative; Random; SerP; SerPl; SerPlas; Serum; Serum or plasma; SR

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

Levothyroxine absorption Calc [Mass fraction]Levothyroxine absorption in Serum or Plasma by calculationLevothyroxine absorption MFr SerPl CalcLevothyroxine absorptionCHALLevothyroxine Absorption, BloodMFr

Frequently asked questions

Code details

Code90804-6

SystemLOINC

Display nameLevothyroxine absorption Calc [Mass fraction]

DescriptionLevothyroxine absorption

Short nameLevothyroxine absorption MFr SerPl Calc

ComponentLevothyroxine absorption

PropertyMFr

TimingPt

System (specimen)Ser/Plas

ScaleQn

MethodCalculated

ClassCHAL

Example units%

StatusACTIVE

Order/ObservationObservation

Flags

BillableNo

Valid clinical useNo

Source

SourceLOINC

Version2.82

Releasemain

First released2.65

Last changed2.65

Consumer names

Levothyroxine Absorption, Blood

Part names

Levothyroxine absorptionMFrPtSer/PlasQnCalculatedMass fractionPoint 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.