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.

LOINCActiveOrder

LOINC Code 34540-5: Phenytoin free and total panel

Name: LOINC Code 34540-5: Phenytoin free and total panel
Creator: HealthAssure Clinical Team
Published: 2026-05-21T08:59:22.384Z

34540-5 is a LOINC code used to identify Phenytoin free and total panel 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 Phenytoin free & total panel. 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 Phenytoin free & total panel. 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: Order
Panel type: Panel

What it does not mean

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

Key facts

Phenytoin free and total panel - Serum or Plasma
Phenytoin free & total panel
DI-HYDAN; Dilantin; Dilj; Diphenylhydantoin; DPH; DRUG/TOXICOLOGY; Drugs; Epanutin; Fenantoin; FR; Lehydan; Neuro; Neurology; Non-protein bound; Pan; PANEL.DRUG & TOXICOLOGY; Panl; Phenhydan; Phenytoin Free+Total Pnl; PHYT; Pl; Plasma; Plsm; Pnl; Point in time; QNT; Quan; Quant; Quantitative; Random; SerP; SerPl; SerPlas; Serum; Serum or plasma; Sinergina; SR; Tot; Totl; Zentropil

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

Phenytoin free and total panelPhenytoin free and total panel - Serum or PlasmaPhenytoin Free+Total Pnl SerPlPhenytoin free & total panelPANEL.DRUG/TOXFree and Total phenytoin panel, Blood-

Frequently asked questions

Code details

Code34540-5

SystemLOINC

Display namePhenytoin free and total panel

DescriptionPhenytoin free & total panel

Short namePhenytoin Free+Total Pnl SerPl

ComponentPhenytoin free & total panel

Property-

TimingPt

System (specimen)Ser/Plas

ScaleQn

ClassPANEL.DRUG/TOX

StatusACTIVE

Order/ObservationOrder

Flags

BillableNo

Valid clinical useNo

Source

SourceLOINC

Version2.82

Releasemain

First released2.10

Last changed2.73

Consumer names

Free and Total phenytoin panel, Blood

Part names

Phenytoin free & total panel-PtSer/PlasQnPhenytoin free and total panelPoint 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.