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Home > Health Library > Galactosemia Test
Galactose is a sugar that is part of the lactose found in milk and milk products. A galactosemia test is a blood or urine test that checks for enzymes that are needed to change galactose into glucose, a sugar that your body uses for energy. A person with galactosemia doesn't have one of these enzymes, so high levels of galactose build up in the blood or urine.
When galactose builds up in a baby's blood, it can cause liver damage, problems with eating, and intellectual disabilities. 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. In a family with a member who has galactosemia, a genetic test can be done on adults to find out whether they have an increased chance of having a child with the disease.
A galactosemia test is done to:
You do not need to do anything before you have this test.
Talk to your doctor about any concerns you have about the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form .
Tests for galactosemia are done on a blood or urine sample.
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.
The health professional drawing your child's blood will:
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.
A quick sting or a pinch is usually felt when the lancet punctures the skin. Your baby may have a little discomfort with the skin puncture, but this does not last long.
Your baby may feel nothing at all from the needle puncture, or he or she may feel a brief sting or pinch as the needle goes through the skin. Some people feel a stinging pain while the needle is in the vein. But many people do not feel any pain (or have only minor discomfort) after the needle is positioned in the vein. The amount of pain you feel depends on the skill of the health professional drawing the blood, the condition of your baby's veins, and your baby's sensitivity to pain.
A baby will usually feel no discomfort from the use of a urine collection bag. But removing the tape that attaches the bag to the skin may cause temporary discomfort.
There is very little risk of a problem from a heel stick. Your baby may get a small bruise at the puncture site.
There is very little chance of a problem from having blood drawn from a vein.
There are no risks linked with a urine test for galactosemia. Removing the tape that holds the bag in place may cause mild skin irritation.
A galactosemia test is a blood or urine test that checks for the enzymes that are needed to change galactose into glucose, a sugar that your body uses for energy.
Negative (galactosemia is not present)
Positive (galactosemia is present)
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
18.5–28.5 units per gram (U/g) of hemoglobin (1.19–1.84 milliunits per mole of hemoglobin [mU/mol Hb]): The person does not have galactosemia.
Less than 5 U/g of hemoglobin (less than 0.32 mU/mol Hb): The person has galactosemia.
5–18.5 U/g of hemoglobin (0.32–1.18 mU/mol Hb): The person may be a carrier of galactosemia and able to pass the disease on to his or her child.
Adults: 12–40 milliunits per gram of hemoglobin (mU/g Hb) (200–667 pkat/g Hb)
Children 2–18 years: 11–54 mU/g Hb (183–900 pkat/g Hb)
Children 0–2 years: 11–150 mU/ g Hb (183–2500 pkat/g Hb)
Lower-than-normal values, depending on age
A newborn screening test that shows the baby has an increased risk of galactosemia will be confirmed by other tests.
Many conditions can change galactose levels. Your doctor will discuss any significant abnormal results with you in relation to your baby's symptoms and past health.
Reasons you may not be able to have the test or why the results may not be helpful include:
Fischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health.
Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.
Other Works Consulted
Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Current as of: December 9, 2019
Author: Healthwise StaffMedical Review: Kathleen Romito, MD - Family MedicineMartin J. Gabica, MD - Family MedicineAdam Husney, MD - Family MedicineSiobhan M. Dolan, MD, MPH - Reproductive Genetics
Current as of: December 9, 2019
Author: Healthwise Staff
Medical Review:Kathleen Romito, MD - Family Medicine & Martin J. Gabica, MD - Family Medicine & Adam Husney, MD - Family Medicine & Siobhan M. Dolan, MD, MPH - Reproductive Genetics
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