Health Encyclopedia


Does this test have other names?

Galactosemia newborn screen, quantitative erythrocyte galactose-1-phosphate uridyltransferase (GALT) analysis 

What is this test?

This test looks for enzymes in the red blood cells in your child's blood.

Galactosemia is a rare inherited disorder that keeps the body from breaking down a simple sugar called galactose. Galactose is found in lactose. Lactose is the sugar found in many kinds of foods and in all dairy products. Normally when you eat something that has lactose, your body breaks lactose down into galactose and glucose. A child who inherits the genes that prevent the breakdown of galactose ends up with too much of it in his or her blood. This condition is called galactosemia. Galactosemia can cause serious problems. These include an enlarged liver, kidney failure, and brain damage.

Out of many types of galactosemia, researchers have found three main gene mutations:

  • Mutations in the GALT gene cause classic type I. This mutation stops normal processing of galactose. It can be life-threatening within a few days after birth. These newborns may fail to thrive and refuse to eat. They may develop jaundice and possibly liver damage. Longer-term problems include cataracts, an increased risk for delayed development, speech difficulties, and reproductive problems from ovarian failure. Type I requires a mutated GALT gene from both parents. If only one parent has a mutated GALT gene and the other has a Duarte variant, then the child will be able to process some galactose. Symptoms of Duarte galactosemia are much less severe.

  • Mutations in the GALK1 gene create type II galactosemia. This is also called galactokinase deficiency. Infants with this type of galactosemia can get cataracts but usually don't have long-term complications.

  • Mutations in the GALE gene create type III galactosemia. This is also called galactose epimerase deficiency. This last type is quite rare. The symptoms vary from mild to severe. Cataracts, intellectual disability, kidney problems, liver disease, and delayed growth are all possible with type III galactosemia.

Why does my child need this test?

This test is part of routine newborn screening. If the routine test comes back positive, you will no longer be able to breastfeed your child. Your child can have soy or another nondairy formula. Further tests will be ordered to figure out which type of galactosemia your child has.

Your child might also have this test at follow-up visits if he or she has galactosemia and the healthcare provider is watching the deficiency.

Girls may need more frequent follow-up to watch for ovarian failure so that appropriate treatment can be given. Both boys and girls are monitored for growth delay, cataracts, and neurodevelopmental problems.

What other tests might my child have along with this test?

Your child's healthcare provider will order other tests to find out which type of deficiency your child has. 

What do my child's test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your healthcare provider.

Normal results show enzyme activity in your child's red blood cells.

Results that show less or no enzyme activity mean that your child may have galactosemia.

How is this test done?

This test requires a blood sample, which is usually taken by a heel prick in the first week of life.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, or bruising.

What might affect my child's test results?

Having breastmilk will affect your child's results. So will having a blood transfusion.

How do I get my child ready for this test?

Your child doesn't need to prepare for this test. 

Medical Reviewers:

  • Taylor, Wanda L, RN, PhD
  • Ziegler, Olivia Walton, MS, PA-C