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Test ID GALP Galactose, Quantitative, Plasma

Useful For

Screening for galactosemia


Galactose-1-phosphate uridyltransferase (GALT) deficiency is the most common cause of galactosemia and requires lifelong restriction of dietary galactose.


Plasma galactose can be elevated in patients with galactosemia caused by either galactose-1-phosphate uridyltransferase (GALT) deficiency or galactokinase (GALK) deficiency.


Classic galactosemia can be diagnosed by analysis of GALT enzyme.

Method Name

Spectrophotometric, Kinetic

Reporting Name

Galactose, QN, P

Specimen Type

Plasma Na Heparin

Advisory Information

This test is not recommended for follow-up of positive newborn screening results. For this purpose GAL1P / Galactose-1-Phosphate (Gal-1-P), Erythrocytes and GCT / Galactosemia Reflex Test, Blood are the most appropriate tests.


This test is not appropriate for the diagnosis of galactosemia. For diagnosis, see GCT / Galactosemia Reflex, Blood.


The preferred test for monitoring dietary therapy is GAL1P / Galactose-1-Phosphate (Gal-1-P), Erythrocytes.

Specimen Required

Collection Container/Tube: Green top (sodium heparin)

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Specimen Minimum Volume

0.2 mL

Specimen Stability Information

Specimen Type Temperature Time
Plasma Na Heparin Frozen (preferred) 365 days
  Ambient  20 days
  Refrigerated  20 days

Reference Values

≤7 days: <5.4 mg/dL

8-14 days: <3.6 mg/dL

≥15 days: <2.0 mg/dL

Day(s) and Time(s) Performed


Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
GALP Galactose, QN, P 2308-5


Result ID Test Result Name Result LOINC Value
83638 Galactose, QN, P 2308-5

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

Testing Algorithm

This is a screening test only.


See Galactosemia Testing Algorithm in Special Instructions.


1. Biochemical Genetics Patient Information (T602) in Special Instructions

2. If not ordering electronically, complete, print, and send an Inborn Errors of Metabolism Test Request (T798) with the specimen.