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.
Galactose tests (blood or urine)
Negative (galactosemia is not
Positive (galactosemia is
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.
Galactose-1-phosphate uridyltransferase (GALT) test (blood)
units per gram (U/g) of hemoglobin (1.19–1.84
milliunits per mole of hemoglobin [mU/mol Hb]): The person does not have
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.
Galactokinase enzyme test (blood)
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
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
What Affects the Test
Reasons you may not be able to
have the test or why the results may not be helpful include:
- A blood transfusion.
placement of a urine collection bag on a baby.
What To Think About
- Early detection and treatment of galactosemia
is very important, because the disease can cause brain damage, liver failure,
cataracts if it is not treated. Within 24 hours of
drinking breast milk or formula, galactose blood levels in a baby with
galactosemia start to rise. A galactosemia test 2 to 3 days after birth will
show whether your baby has galactosemia. Almost all states in the United
States have laws that require galactosemia testing of newborns within a few
days of birth.
- If your baby's test is positive, the test will be
repeated to confirm the diagnosis.
- If test results confirm that
your baby has galactosemia, ask to speak to a
dietitian. A substitute for breast milk or milk-based
formula, such as formula made from soy, will prevent damage caused
by galactosemia. It will never be safe to give milk or milk products to a child
who has galactosemia.
- If you or your partner knows that you are a carrier of
galactosemia or if you have family members with galactosemia, you may want to
genetic counseling to learn about the disease and the
likelihood of passing it to your children. To learn more, see the