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GALT Blood Test

Last updated June 2, 2019

Approved by: Krish Tangella MD, MBA, FCAP

The GALT Blood Test helps determine the level of GALT in blood. It is used to screen newborns for galactosemia and to identify the cause of galactosemia in adults.

What are other Names for this Test? (Equivalent Terms)

  • G-1-PU Blood Test
  • Galactose-1-Phosphate Uridyltransferase Blood Test
  • Galactosemia Enzyme Blood Test

What is GALT Blood Test? (Background Information)

  • Galactose-1-phosphate uridyltransferase (GALT) is an enzyme that converts the simple sugar galactose to glucose, another simple sugar that provides the body’s main source of energy
  • Two other enzymes also perform this function and they include galactokinase (GALK) and uridine diphosphate galactose-4-epimerase (GALE)
  • Galactose is found mainly in dairy products. It is a component of lactose, a complex sugar that is broken down into galactose and glucose by the enzyme lactase
  • Low levels of GALT, GALK, and GALE limits the body’s ability to metabolize galactose. This causes galactose accumulation in red blood cells, which leads to a condition known as galactosemia
  • Most cases of GALT abnormalities arise from mutations in the GALT gene, which gives instructions for the GALT enzyme. This makes galactosemia primarily a genetic disorder
  • Galactosemia is associated with tissue damage and developmental abnormalities. It should be identified as soon as possible, so that a galactose-restricted diet may be started
  • The GALT Blood Test helps determine the level of GALT in blood. It is used to screen newborns for galactosemia and to identify the cause of galactosemia in adults

What are the Clinical Indications for performing the GALT Blood Test?

Following are the clinical indications for performing the GALT Blood Test:

  • Screening for newborns at risk for galactosemia
  • Nausea
  • Vomiting
  • Developmental defects or abnormalities
  • Yellowing of the skin and white of the eyes

How is the Specimen Collected for GALT Blood Test?

Following is the specimen collection process for GALT Blood Test:

Sample required: Blood

Process of obtaining blood sample in adults:

  • A band is wrapped around the arm, 3-4 inches above the collection site (superficial vein that lies within the elbow pit)
  • The site is cleaned with 70% alcohol in an outward spiral, away from the zone of needle insertion
  • The needle cap is removed and is held in line with the vein, pulling the skin tight
  • With a small and quick thrust, the vein is penetrated using the needle
  • The required amount of blood sample is collected by pulling the plunger of the syringe out slowly
  • The wrap band is removed, gauze is placed on the collection site, and the needle is removed
  • The blood is immediately transferred into the blood container, which has the appropriate preservative/clot activator/anti-coagulant
  • The syringe and the needle are disposed into the appropriate “sharp container” for safe and hygienic disposal

Preparation required: No special preparation is needed prior to the test.

What is the Significance of the GALT Blood Test Result?

A low value (less than 14.7 U/g of hemoglobin) for the GALT Blood Test may indicate galactosemia.

  • Individuals with galactosemia must start a galactose-restricted diet as soon as possible. Foods, such as dairy products, should be avoided, as the lactose they contain is broken down into glucose and galactose
  • A galactose-restricted diet should prevent galactose accumulation in blood, and therefore the symptoms of galactosemia

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • The GALT Blood Test identifies a GALT deficiency, which is probably caused by a genetic mutation. However, a separate genetic test must be performed to identify the mutation that has occurred

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider of the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

The following DoveMed website links are useful resources for additional information:



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References and Information Sources used for the Article:

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Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: March 30, 2016
Last updated: June 2, 2019