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.

LOINCActiveBoth

LOINC Code 49135-7: Fractional excretion of sodium (U+S/P) [Ratio]

Name: LOINC Code 49135-7: Fractional excretion of sodium (U+S/P) [Ratio]
Creator: HealthAssure Clinical Team
Published: 2026-05-21T08:59:33.938Z

49135-7 is a LOINC code used to identify Fractional excretion of sodium (U+S/P) [Ratio] 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 Fractional excretion of sodium. It is commonly used with the system or sample type Urine+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 Fractional excretion of sodium. It is commonly used with the system or sample type Urine+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: Both

What it does not mean

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

Key facts

Fractional excretion of sodium [Ratio] in Urine and Serum or Plasma

Fractional excretion of sodium

The fractional excretion of sodium is calculated as follows, where the asterisk is being used to indicate multiplication100 * (urine Na * plasma creatinine)/(plasma Na * urine creatinine). Fractional excretion of sodium is used to try to distinguish pre-renal azotemia (FE Na <1% ) from m actute tubular necrosis (FE Na > 1%) and post renal azotemia (FE Na > 4%).

Chemistry; FE Na; FENa; Fract excret Na; Na; Na+; Pl; Plasma; Plsm; Point in time; QNT; Quan; Quant; Quantitative; Random; Ratios; Rto; SerP; SerPl; SerPlas; Serum; Serum or plasma; SR; UA; UR; Ur+SerPl; Urn

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

Fractional excretion of sodium (U+S/P) [Ratio]Fractional excretion of sodium [Ratio] in Urine and Serum or PlasmaFract excret Na Ur+SerPl-RtoFractional excretion of sodiumCHEMFractional excretion of sodium, Urine+BloodRatio

Frequently asked questions

Code details

Code49135-7

SystemLOINC

Display nameFractional excretion of sodium (U+S/P) [Ratio]

DescriptionFractional excretion of sodium

Short nameFract excret Na Ur+SerPl-Rto

ComponentFractional excretion of sodium

PropertyRatio

TimingPt

System (specimen)Urine+Ser/Plas

ScaleQn

ClassCHEM

Example units%

StatusACTIVE

Order/ObservationBoth

Flags

BillableNo

Valid clinical useNo

Source

SourceLOINC

Version2.82

Releasemain

First released2.21

Last changed2.73

Consumer names

Fractional excretion of sodium, Urine+Blood

Part names

Fractional excretion of sodiumRatioPtUrine+Ser/PlasQnPoint in time (spot)Urine and 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.