A galactosemia test is a blood or urine test that checks for three enzymes that are needed to change galactose-a sugar that is found in milk and milk products-into glucose, a sugar that your body uses for energy. A person with galactosemia doesn't have one of these enzymes. This causes high levels of galactose in the blood or urine.

When galactose builds up in a baby's blood, it can cause brain damage, seizures, and mental retardation. The damage caused by galactosemia can begin within weeks after the baby has started drinking breast milk or formula. Babies with galactosemia need foods low in galactose in order to gain weight and to prevent brain damage, liver problems, infection, and cataracts.

Galactosemia is a rare disease that is passed from parents to children (inherited genetic disorder). A galactosemia test is usually done to determine whether a newborn has the disease. A genetic test is done on adults to determine whether they have an increased chance of having a child with the disease.

Why It Is Done

A galactosemia test is done to:

• Determine whether a newborn has the enzymes needed to change galactose into glucose.
• Monitor the effectiveness of diet changes for a child with galactosemia.

How To Prepare

No special preparation is required before having this test.

Talk to your health professional about any concerns you have about the need for the test, its risks, how it will be done, or what the results will indicate. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

How It Is Done

Tests for galactosemia are done on a blood or urine sample.

Blood sample from a heel stick

If galactosemia testing is done on a baby, a heel stick will be done instead of a blood draw from a vein. For a heel stick blood sample, several drops of blood are collected from the heel of the baby. The skin of the heel is cleaned with alcohol and then punctured with a sterile lancet. Several drops of blood are collected inside circles on a specially prepared piece of paper. When enough blood has been collected, a gauze pad or cotton ball is placed over the puncture site. Pressure is maintained on the puncture site briefly to stop the bleeding, and then a small bandage is usually applied. A blood sample is usually collected within 2 to 3 days after birth.

If the test shows that the baby has galactosemia, the results will be confirmed on a blood sample taken from a vein.

Blood sample from a vein

The health professional drawing your child's blood will:

• Wrap an elastic band around your child's upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your child's arm when enough blood is collected.
• Apply a gauze pad or cotton ball over the needle site as the needle is removed.
• Apply pressure to the site and then a bandage.

Urine sample

To test for galactose in a urine sample from a baby, a health professional will tape a plastic collection bag to the baby's genital area. After the baby urinates, the collection bag is removed. A blood test for galactose is more accurate than a urine test.