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What Is Galactosemia?

Galactosemia is a metabolic disorder that some babies are born with. It's caused by a problem with the enzymes that break down the sugar galactose. Babies with galactosemia (geh-lak-teh-SEE-mee-uh) have high levels of galactose in their blood.

Lactose is the main type of sugar in milk, milk-based formulas, and breast milk. Lactose is made up of glucose and galactose. That's why babies with galactosemia can't have milk and dairy products.

There are three types of galactosemia, depending on which enzyme doesn't work. The most common and severe type is called classic galactosemia.

What Are the Signs & Symptoms of Galactosemia?

Signs of classic galactosemia usually start in a baby's first week of life. They include:

  • poor feeding
  • vomiting
  • fussiness or irritability
  • yellow skin and eyes (jaundice) and a big liver
  • cataracts (cloudy eye lenses)
  • blood infections (sepsis)

If the condition isn't treated, a baby may have trouble growing and gaining weight, and slowed development.

How Is Galactosemia Diagnosed?

All newborn babies in the United States have their blood tested for signs of galactosemia as part of newborn screening.

Doctors also do other tests if they suspect galactosemia, such as:

How Is Galactosemia Treated?

Untreated galactosemia can lead to liver damage, kidney failure, and intellectual disabilities. So doctors will put babies with galactosemia on a soy formula (which doesn't contain lactose) as soon as possible. Babies must drink soy-based formula instead of breast milk or a cow's milk-based formula. Milk-based "lactose-free" formulas are not recommended.

Kids with classic galactosemia must continue to keep milk and other dairy products out of their diets. Most will need to take calcium supplements.

Children with milder types of galactosemia might be able to have some dairy. That's because the enzymes that break down galactose are partially working.

What Causes Galactosemia?

Galactosemia happens when there's a change (mutation) in the genes that make an enzyme that breaks down galactose. To have galactosemia, a child must inherit two galactosemia genes, one from each parent.

In galactosemia, galactose and its byproducts build up in the blood. This can damage cells and parts of the body.

What Else Should I Know?

Early diagnosis and treatment can help reverse cataracts, aid growth, and improve liver and kidney problems. Even with good dietary treatment, children with galactosemia may have:

  • weak bones
  • speech and learning problems
  • ovarian failure (delayed puberty, irregular or no periods, inability to become pregnant)

Doctors will closely watch kids who have galactosemia. They'll check their growth and development, do eye exams to look for cataracts, and measure galactose levels in the blood.

Because galactosemia is a genetic condition, consider speaking to a genetic counselor about testing other family members and to learn how galactosemia runs in families.

You also can find more information and support online at:

Reviewed by: Michael F. Cellucci, MD
Date Reviewed: Jul 2, 2022

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