To have the disease, a child must inherit the tendency from both parents. For each pregnancy, in such a family, there is a 1 in 4 chance a baby will be born with the deficiency. Because of the potential disastrous side effects of late diagnosis, many states have mandatory neonatal screening programs for galactosemia. The disease usually appears in the first days of life following the ingestion of breast milk or formula. If unrecognized in the newborn period, the disease may produce liver, brain, eye and kidney damage.
Blood tests can make the diagnosis.
The disease is detected by measuring the level of enzyme in red blood cells, white blood cells or liver. A galactose tolerance test should never be done, as it may be harmful. Affected infants who ingest galactose will excrete it in large quantities in their urine where it can also be detected. If the infant is vomiting, and not taking milk, the test can be negative. If the disease is suspected, the diagnosis should be confirmed by blood testing.