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Test Code GALP Galactose, Quantitative, Plasma

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful For

Screening for galactosemia

Testing Algorithm

This is a screening test only.


See Galactosemia Testing Algorithm in Special Instructions.

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

Reject Due To


Mild OK; Gross OK


Mild OK; Gross OK





Reference Values

1-7 days: <5.4 mg/dL

8-14 days: <3.6 mg/dL

>14 days: <2.0 mg/dL


Additional testing is required to investigate the cause of abnormal results.


In patients with galactosemia, elevated galactose in plasma or urine may suggest ineffective dietary restriction or compliance; however, the concentration of galactose-1-phosphate in erythrocytes (GAL1P / Galactose-1-Phosphate [Gal-1-P], Erythrocytes) is the most sensitive index of dietary control. Increased concentrations of galactose may also be suggestive of severe hepatitis, biliary atresia of the newborn, and, in rare cases, galactose intolerance.


If results are outside the normal range and galactosemia is suspected, additional testing to identify the specific enzymatic defect is required. Results should be correlated with clinical presentation and confirmed by specific enzyme or molecular analysis. See Galactosemia Testing Algorithm in Special Instructions for follow-up of abnormal newborn screening results, comprehensive diagnostic testing, and carrier testing. See GALT / Galactose-1-Phosphate Uridyltransferase (GALT), Blood for GALT testing, GALK / Galactokinase, Blood for GALK testing, and GALE / UDP-Galactose-4’ Epimerase (GALE), Blood for GALE testing.

Day(s) and Time(s) Performed


Analytic Time

8 days

Specimen Retention Time

1 month

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.

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


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.