Symptoms:

• Jaundice (yellowish discoloration of the skin and the whites of the eyes)
• Vomiting
• Poor feeding (baby refusing to drink milk-containing formula)
• Poor weight gain
• Lethargy
• Irritability
• Convulsions

Signs and tests:

• Hepatomegaly (enlarged liver)
• Hypoglycemia (low blood sugar)
• Aminoaciduria (amino acids are present in the urine and/or blood plasma)
• Cirrhosis
• Ascites (fluid collects in the abdomen)
• Mental retardation
• Cataract formation

Tests include:

• Prenatal diagnosis by direct measurement of the enzyme galactose-1-phosphate uridyl transferase 
• The presence of "reducing substances" in the infant's urine with normal or low blood sugar while the infant is being fed breast milk or a formula containing lactose. A simple test on the urine indicates the presence of a reducing substance, and a specific enzymatic study on the urine can prove the substance to be galactose.
• Presence of chemicals, called ketones, in the urine
• Measurement of enzyme activity in the red blood cells
• Blood culture for bacteria infection (E. coli sepsis)