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 10634-4: Complement C1 esterase inhibitor.functional/Complement C1 esterase inhibitor.total [Mass fraction]

Name: LOINC Code 10634-4: Complement C1 esterase inhibitor.functional/Complement C1 esterase inhibitor.total [Mass fraction]
Creator: HealthAssure Clinical Team
Published: 2026-05-21T11:17:19.668Z

10634-4 is a LOINC code used to identify Complement C1 esterase inhibitor.functional/Complement C1 esterase inhibitor.total [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 Complement C1 esterase inhibitor.functional/Complement C1 esterase inhibitor.total. 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 Complement C1 esterase inhibitor.functional/Complement C1 esterase inhibitor.total. 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: Both

What it does not mean

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

Key facts

Complement C1 esterase inhibitor.functional/Complement C1 esterase inhibitor.total in Serum or Plasma

Complement C1 esterase inhibitor.functional/Complement C1 esterase inhibitor.total

Functional C1 esterase inhibitor is reported as % means "percent of functional over mean normal" by many commonly used kits. This is reported by LOINC code 48494-9. Many sites have incorrectly mapped to [LOINC10634-4] (functional /Total) which is not the component reported by the commonly used methods.

C1 inactivator; C1 inhibiting factor; C1INA; C1INH; C1-INH; C1INH Functional; C1INH Total; Comp; Complmt; HEMATOLOGY/CELL COUNTS; Inhib; Inhibit; Mass fraction; Percent; Pl; Plasma; Plsm; Point in time; QNT; Quan; Quant; Quantitative; Random; SerP; SerPl; SerPlas; Serum; Serum or plasma; SR; Tot; Totl; UniversalLabOrders

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

Complement C1 esterase inhibitor.functional/Complement C1 esterase inhibitor.total [Mass fraction]Complement C1 esterase inhibitor.functional/Complement C1 esterase inhibitor.total in Serum or PlasmaC1INH Functional/C1INH Total MFr SerPlComplement C1 esterase inhibitor.functional/Complement C1 esterase inhibitor.totalHEM/BCComplement C1 Esterase Inhibitor.functional/Complement C1 Esterase Inhibitor.total, BloodMFr

Frequently asked questions

Code details

Code10634-4

SystemLOINC

Display nameComplement C1 esterase inhibitor.functional/Complement C1 esterase inhibitor.total [Mass fraction]

DescriptionComplement C1 esterase inhibitor.functional/Complement C1 esterase inhibitor.total

Short nameC1INH Functional/C1INH Total MFr SerPl

ComponentComplement C1 esterase inhibitor.functional/Complement C1 esterase inhibitor.total

PropertyMFr

TimingPt

System (specimen)Ser/Plas

ScaleQn

ClassHEM/BC

Example units%

StatusACTIVE

Order/ObservationBoth

Flags

BillableNo

Valid clinical useNo

Source

SourceLOINC

Version2.82

Releasemain

First released1.0i

Last changed2.73

Consumer names

Complement C1 Esterase Inhibitor.functional/Complement C1 Esterase Inhibitor.total, Blood

Part names

Complement C1 esterase inhibitor.functional/Complement C1 esterase inhibitor.totalMFrPtSer/PlasQnMass 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.