Galactosemia is a rare but serious genetic metabolic disorder that affects how the body processes a sugar called galactose. If left undetected, it can cause life-threatening damage to the liver, kidneys, brain, and eyes. Fortunately, Canadian newborn screening programmes identify most cases at birth, and the condition can be managed effectively through a strict diet.
What Is Galactosemia?
Galactosemia means “galactose in the blood.” The body normally breaks down galactose, a sugar found in milk and dairy products, into energy. However, people with galactosemia lack a key enzyme needed to do this job.
Without this enzyme, galactose builds up to harmful levels in the blood. This buildup damages vital organs and can be fatal if not caught early. In Canada, most babies are screened for galactosemia shortly after birth as part of provincial newborn screening programmes.
The Two Main Types of Galactosemia
There are two main forms of galactosemia. The first and more severe form is classic galactosemia, caused by a deficiency of an enzyme called GALT (galactose-1-phosphate uridylyltransferase). The second form is galactokinase deficiency, which is generally milder.
Classic galactosemia is the type most commonly diagnosed through newborn screening. It causes a toxic buildup of a substance called galactose-1-phosphate, which harms the liver, brain, kidneys, and eyes. Both types are inherited as autosomal recessive traits, meaning a child must receive a defective gene from each parent to develop the condition.
What Causes Galactosemia?
Galactosemia is caused by a change (mutation) in a gene that controls the production of enzymes needed to break down galactose. The gene responsible for classic galactosemia is called GALT, located on chromosome 9p13.
Galactose comes mainly from lactose, the sugar found in milk. Lactose is made up of two simpler sugars — galactose and glucose — linked together. When a baby with galactosemia drinks breast milk or regular formula, the galactose cannot be processed properly. As a result, it rapidly builds up in the body and causes damage.
Because galactosemia is inherited, parents who each carry one defective copy of the gene have a 25% chance with each pregnancy of having a child with the condition. Genetic counselling is available through many provincial health programmes across Canada for families with a history of this disorder.
Recognising the Symptoms of Galactosemia
Symptoms of galactosemia can appear within the first few days of life, as soon as a newborn begins drinking breast milk or lactose-containing formula. The signs can come on quickly and become serious very fast.
In addition, some early symptoms can be caused or worsened by a serious blood infection with the bacterium E. coli, which newborns with galactosemia are more vulnerable to. Therefore, parents should seek medical help immediately if they notice any of the following signs.
Common Symptoms in Newborns and Infants
Jaundice — yellowing of the skin and eyes
Vomiting shortly after feeding
Irritability and excessive crying
Lethargy — unusual tiredness or limpness
Refusal to feed or poor feeding
Poor weight gain despite regular feeding
Seizures
Enlarged liver (hepatomegaly)
Fluid buildup in the abdomen (ascites)
Low blood sugar (hypoglycaemia)
Amino acids in the urine (aminoaciduria)
If galactosemia is not diagnosed and treated quickly, it can lead to lasting problems. These include intellectual disability, cataracts (clouding of the eye’s lens), liver failure, and kidney damage. This is why early diagnosis is so critical.
How Is Galactosemia Diagnosed?
In Canada, all newborns are tested for galactosemia as part of provincial newborn screening programmes. A small blood sample — usually taken from the baby’s heel within the first 24 to 48 hours after birth — is tested for enzyme activity. Each province manages its own screening programme, so specific procedures may vary slightly.
However, if symptoms appear before results return, or if screening was not completed, doctors can order additional tests. Early testing is essential because even a brief delay can allow significant harm to occur.
Diagnostic Tests for Galactosemia
A doctor may order several tests to confirm a galactosemia diagnosis. These tests help identify the type and severity of the condition.
Enzyme activity tests — these measure GALT enzyme activity in red blood cells
Blood cultures — used to check for bacterial infections, especially E. coli
Urine tests — to detect ketone bodies and abnormal amino acid levels
Prenatal testing — measuring galactose-1-phosphate uridylyltransferase enzyme activity before birth, for families with a known history of galactosemia
If you have a family history of galactosemia, speak with your family doctor or a genetic counsellor. They can advise you on whether prenatal testing is right for your situation. For more information on metabolic disorders and newborn screening, visit Health Canada’s official health resources.
Treating Galactosemia: The Role of Diet
Currently, the only treatment for galactosemia is a strict, lifelong restriction of galactose in the diet. There is no medication that replaces the missing enzyme. However, with careful dietary management, many people with galactosemia live healthy lives.
Because lactose — the sugar in milk — is made up of galactose and glucose, all milk-based products must be completely avoided. This applies from birth onwards. Infants with galactosemia must be switched immediately to a lactose-free or soy-based formula.
Foods to Avoid With Galactosemia
People with galactosemia must avoid all foods and ingredients that contain galactose or lactose. This requires careful reading of food labels at all times. The following items must be avoided:
Breast milk and all animal milks
Butter and cream
Cheese and yoghurt
Dry milk solids or milk powder
Sour cream and whipped cream
Milk chocolate and chocolate products containing milk
Casein and whey (common ingredients in processed foods)
Margarine containing dairy ingredients
Other Foods That May Need to Be Limited
In addition to dairy products, some other foods contain small amounts of galactose. A registered dietitian can help create a personalised meal plan. Foods that may need to be limited or monitored include:
Certain fruits and vegetables (such as watermelon, papaya, and some legumes)
Organ meats such as liver, heart, kidneys, and pancreas
Fermented soy products
Hydrolysed meat proteins
Monosodium glutamate (MSG)
Furthermore, some medications and supplements have coatings or fillers that contain lactose or galactose. Always read the label carefully. Ask your pharmacist to check ingredients before taking any new medication or supplement.
For a detailed overview of how metabolic disorders are managed through nutrition, Mayo Clinic’s galactosemia treatment guide offers helpful information reviewed by medical specialists.
Long-Term Outlook for People With Galactosemia
With early diagnosis and a strict galactose-free diet, many complications of galactosemia can be prevented. However, even with excellent dietary control, some individuals may still experience certain long-term challenges. Researchers believe this may be because the body produces small amounts of galactose on its own.
Possible long-term issues include speech and language delays, learning difficulties, and in females, premature ovarian insufficiency (early menopause). Regular follow-up with a metabolic specialist, dietitian, and other healthcare providers is important throughout life.
Many children and adults with galactosemia lead full and productive lives. Ongoing support from your healthcare team, including access to provincial programmes and specialist referrals, makes a real difference in long-term outcomes. You can also explore Healthline’s guide to living with galactosemia for practical lifestyle tips.
When to See a Doctor
If your newborn shows any signs of galactosemia — such as jaundice, vomiting, poor feeding, or unusual lethargy — contact your family doctor or go to a walk-in clinic right away. Do not wait for scheduled newborn screening results if you are concerned.
If your baby appears very unwell, go directly to your nearest emergency room. Galactosemia can worsen rapidly in the first days of life. Early treatment is the key to preventing serious, lasting harm.
If there is a family history of galactosemia or other metabolic disorders, speak with your family doctor before or during pregnancy. They can refer you to a genetic counsellor or metabolic specialist through your provincial health plan. As always, speak with a qualified healthcare provider before making any changes to your child’s diet or feeding routine.
Frequently Asked Questions About Galactosemia
What is galactosemia in simple terms?
Galactosemia is a rare genetic condition where the body cannot properly break down galactose, a sugar found in milk. Without a key enzyme, galactose builds up in the blood and damages organs. It is usually detected through newborn screening shortly after birth.
Can babies with galactosemia be breastfed?
No. Babies with galactosemia cannot be breastfed because breast milk contains lactose, which breaks down into galactose. Infants diagnosed with galactosemia must be switched immediately to a lactose-free or soy-based infant formula. Your healthcare provider will guide you on the right alternative feeding plan.
Is galactosemia screened for in Canada?
Yes. Galactosemia is included in newborn screening programmes across most Canadian provinces. A small blood sample is taken from the baby’s heel shortly after birth and tested for enzyme activity. Each province manages its own screening programme, so coverage may vary slightly.
Is there a cure for galactosemia?
There is currently no cure for galactosemia. The only treatment is a strict, lifelong diet that avoids all foods containing galactose or lactose. However, when managed carefully from birth, many complications of galactosemia can be prevented or minimised.
What happens if galactosemia is left untreated?
If galactosemia goes undetected and untreated, it can cause serious and permanent damage. This includes liver failure, intellectual disability, cataracts, and kidney damage. In severe cases, untreated galactosemia can be fatal, which is why newborn screening is so important.
Can people with galactosemia eat any dairy at all?
No. People with galactosemia must completely avoid all dairy products and any foods containing lactose or galactose. This includes milk, cheese, butter, cream, and many processed foods that use dairy as an ingredient. A registered dietitian can help create a safe and nutritious meal plan.
Key Takeaways
Galactosemia is a rare genetic disorder that prevents the body from processing galactose, a sugar in milk.
The most common and serious form is classic galactosemia, caused by a GALT enzyme deficiency.
Symptoms can appear within days of birth and include jaundice, vomiting, poor feeding, and seizures.
Canadian newborn screening programmes test for galactosemia shortly after birth in most provinces.
The only treatment is a strict, lifelong galactose-free diet, starting with lactose-free or soy-based infant formula.
Many medications and processed foods contain hidden lactose — always check labels and ask your pharmacist.
With early diagnosis and careful dietary management, many people with galactosemia live full, healthy lives.
If you have concerns about your newborn or a family history of galactosemia, speak with your family doctor or visit a walk-in clinic as soon as possible.
