What Is Glucose Galactose Malabsorption?

  • Maha AhmedMBBS, Intarnal Medicine and General Surgery, Cairo University, Egypt


When a child is born, parents try to identify which characteristics resemble them; sometimes, it could be the nose, eyes or smile of the child. The physical resemblance between a parent and a child involves genetic inheritance. Sometimes, children can also inherit disease genes from their parents. One of them is Glucose Galactose Malabsorption, also known as GGM. This is a rare genetic metabolic disorder that is caused by a deficiency in the transportation of glucose and galactose through the intestinal lining.1   

The disease usually starts very early in life, as early as the first day of life. The disease can cause severe and chronic diarrhoea if the patient consumes sucrose (table sugar), lactose (milk sugar), glucose and galactose, and it can cause death if they are not removed from the diet.2 It is important to highlight that GGM is not the same as lactose intolerance.  

Causes of glucose galactose malabsorption

GGM is caused by a genetic mutation in the protein called SGLT1, located on chromosome 22, responsible for the transportation of galactose and glucose from the digestive tract to the bloodstream.2 The SGLT1 protein is located through the intestinal tract and the kidneys. SGLT 1 in the kidneys is in charge of maintaining normal levels of blood glucose; it ensures that sugar goes back into the bloodstream and is not let out into the urine.1  

The mutation of the SGLT1 protein impedes the absorption of glucose and galactose, causing the water that is supposed to be carried across the membrane with the sugars to stay in the intestinal tract and evacuate through the stool.4 Which provokes severe dehydration and diarrhoea in patients.

This disease is inherited in an autosomal recessive pattern, which means that both parents carry one copy of the mutated gene and transmit it to the patient.2 Usually, the parents do not show any signs or symptoms of the genetic disorder. 2 

Signs and symptoms

The signs and symptoms of GGM are characterised by a dimension of gastrointestinal symptoms that are due to the inability to properly absorb glucose and galactose. The symptoms appear very early in life during exposure to breast milk or formulas because of their composition of glucose and galactose elements. Among the symptoms we have:5

  • Diarrhoea: it is the most prominent symptom of GGM; severe chronic diarrhoea can cause life-threatening dehydration.4
  • Abdominal pain: due to the range of gastrointestinal complications, a GGM patient might experience serious abdominal pain or discomfort. Sugar in the intestinal tract can provoke irritation and cramping.4 
  • Raised acidity in the blood and tissues, better known as acidosis. 
  • Bloating and Gas: the irregular presence of sugars in the intestines makes the body susceptible to gas production and bloating.3  
  •  Failure to Thrive: children with GGM  can experience poor weight gain and growth as a result of the disruption of nutrient absorption.5 
  • Sugar in the urine 
  • Growth of kidney stones 
  • Excessive urination 

Diagnosis of glucose galactose malabsorption

GGM is usually diagnosed after an individual presents signs of the disease, especially severe and ongoing diarrhoea.3 Doctors will do a clinical assessment, symptoms evaluation and a physical examination; these will help to tell the nature and duration of the symptoms and see if they align with GGM.4 If the symptoms align with a potential case of GGM, doctors will order a series of laboratory tests: hydrogen breath test, genetic testing and stool analysis. The first one consists of measuring the level of hydrogen after a couple of minutes of consuming a solution that contains glucose and galactose.5 An increased concentration level of hydrogen indicates malabsorption of glucose and galactose. The second one consists of identifying particular mutations in the SGLT1 gene.3 The third one identifies the presence of undigested sugars in the stool.1 

Management and treatment

Currently, there is no cure for GGM, but there are lifestyle changes to prevent patients from developing episodes of severe diarrhoea. 

  • GGM patients will go under dietary restrictions to prevent severe symptoms from appearing. Among the dietary restrictions is the recommendation to avoid high-glucose and high-galactose foods, such as specific vegetables, fruits, dairy products, and processed foods. Some of the sugars can be replaced by fructose-based nutrients as fructose is processed differently in the body from glucose and galactose.6   
  • A GGM patient must have a specialized dietitian to develop a healthy diet and ensure that the patient gets all the essential nutrients to need it. The dietitian will also provide advice about potential nutritional supplements that could need it.6  
  • Some health practitioners may recommend the use of probiotics and enzyme replacement therapy to help reduce digestive symptoms and better gut health.4  
  • Patients need regular monitoring to assess symptom severity, adjust management plans as needed, and check the nutritional status and growth (in the case of infants).3 

Risk factors and complications

If GGM is not treated at the correct time, it can lead to several potential risks and complications. 

  • Failure to Thrive. Children with untreated GGM may have inadequate growth and weight gain provoked by insufficient nutrient absorption.6 
  • Malnutrition. The failure to absorb glucose and galactose may lead to inadequate nutrient intake, which leads to malnutrition. This causes problems in development, growth and overall health.6 
  • Electrolyte imbalance and dehydration. Chronic diarrhoea leads to severe dehydration and electrolyte imbalance because there is not sufficient fluid intake to compensate for the fluid loss, causing low levels of potassium and sodium.4   
  • Bone issues. The recommended dietary restriction of dairy products can have an impact on the calcium intake of patients, which can lead to weakened bones and a risk of fractures.4 
  • Gastrointestinal discomfort. Untreated GGM drives several gastrointestinal symptoms, including abdominal pain, diarrhoea, gas and bloating, causing a decrease in the quality of life of the patients.2 
  • Reduced quality of life. Untreated symptoms and dietary limitations can impact deeply on the physical and emotional well-being of a patient. Limiting their participation in social activities, travel and enjoying a wide range of food types.5 


How can I prevent GGM?

Glucose Galactose Malabsorption is a genetic hereditary disease, which means that it cannot be prevented from developing. However, a patient can control their dietary intake and avoid episodes of gastrointestinal complications. 

How common is GGM?

Studies show that GGM is a very rare disease. There have been reported around 200 cases worldwide, and most of the cases are presented among female patients. It is also important to point out that approximately 10 % of the population may present a reduced capacity for glucose absorption without associated health problems.5 

What can I expect if I have GGM?

If a patient has GGM, he or she can experience several gastrointestinal complications, malnutrition and severe dehydration. The disease will have a deep impact on their quality of life and dietary adjustments. 

How important is early diagnosis and treatment for GGM?

Early diagnosis and treatment of GGM are crucial to prevent life-threatening symptoms among patients. Proper management of GGM improves patients' quality of life. Among very young patients, it is important to manage the disease to preserve proper growth and development.5

What else is it called?

  • GGM
  • Carbohydrate intolerance
  • SGLT1 deficiency
  • Complex carbohydrate intolerance
  • Congenital glucose-galactose intolerance 
  • Monosaccharide malabsorption

When should I see a doctor?

You should seek a doctor if you or someone that you know presents any of the symptoms mentioned before, especially if they experience severe diarrhoea and abdominal pain


Glucose Galactose Malabsorption is a rare genetic metabolic disorder that is caused by a deficiency in the transportation of glucose and galactose through the intestinal lining. GGM is caused by a genetic mutation in the protein SGLT1, located on chromosome 22, responsible for transporting galactose and glucose from the digestive tract to the bloodstream. The mutation of the SGLT1 causes the water in the digestive system that is supposed to be carried across the membrane with the sugars to stay in the intestinal tract and evacuate through the stool, which provokes severe dehydration and diarrhoea in patients. This disease is inherited in an autosomal recessive pattern, which means that both parents carry one copy of the mutated gene and transmit it to the patient. 


  1. Wright EM. I. Glucose galactose malabsorption. American Journal of Physiology-Gastrointestinal and Liver Physiology [Internet]. 1 November 1998 [cited 10 August 2023];275(5): G879-82. Available on: https://www.physiology.org/doi/10.1152/ajpgi.1998.275.5.G879
  2. Information (US) NC for B. Glucose galactose malabsorption [Internet]. National Center for Biotechnology Information (US); 1998 [cited 10 August 2023]. Available on: https://www.ncbi.nlm.nih.gov/books/NBK22210/
  3. Alderman H, Dilli D, Ceylaner S. A case of congenital glucose-galactose malabsorption with a new mutation in the slc5a1 gene. J Pediatr Genet [Internet]. December 2022 [cited 10 August 2023];11(04):317-9. Available on: http://www.thieme-connect.de/DOI/DOI?10.1055/s-0040-1719161
  4. Wang W, Wang L, Ma M. Literature review on congenital glucose–galactose malabsorption from 2001 to 2019. J Paediatr Child Health [Internet]. November 2020 [cited 10 August 2023];56(11):1779-84. Available on: https://onlinelibrary.wiley.com/doi/10.1111/jpc.14702
  5. Glucose-galactose malabsorption - metabolic support uk [Internet]. 2023 [cited 2023 Nov 15]. Available from: https://metabolicsupportuk.org/condition/glucose-galactose-malabsorption/
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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