Lactose Intolerance

National Organization for Rare Disorders, Inc.

It is possible that the main title of the report Lactose Intolerance is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.


  • Alactasia
  • Disaccharidase Deficiency
  • Glucose-Galactose Malabsorption
  • Hypolactasia
  • Lactase Deficiency
  • Lactase Isolated Intolerance

Disorder Subdivisions

  • Congenital Lactose Intolerance
  • Neonatal Lactose Intolerance
  • Lactose Intolerance of Childhood
  • Lactose Intolerance of Adulthood

General Discussion

Lactose is the predominant sugar found in milk and milk products. People with Lactose intolerance (LI) cannot properly digest lactose because they lack or are deficient in the enzyme, lactase, which is key to the digestion of lactose. Lactose is a complex sugar made up of two different sugar molecules (disaccharide), galactose and glucose, each of which is a simple (monosaccharide) sugar and more readily absorbed in the body's stomach and intestine and processed in other organs.

LI is common among adults in the United States and elsewhere. It is worrisome and uncomfortable but not at all dangerous.

This disorder is an inborn error of carbohydrate metabolism characterized by the impaired ability to absorb nutrients from the small intestine (malabsorption syndrome).


March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains, NY 10605
Tel: (914)997-4488
Fax: (914)997-4763
Tel: (888)663-4637

NIH/National Institute of Diabetes, Digestive & Kidney Diseases
Endocrine Diseases Metabolic Diseases Branch
2 Information Way
Bethesda, MD 20892-3570
Tel: (301)654-3810
Fax: (301)496-7422

MUMS National Parent-to-Parent Network
150 Custer Court
Green Bay, WI 54301-1243
Tel: (920)336-5333
Fax: (920)339-0995
Tel: (877)336-5333

Genetic and Rare Diseases (GARD) Information Center
PO Box 8126
Gaithersburg, MD 20898-8126
Tel: (301)251-4925
Fax: (301)251-4911
Tel: (888)205-2311
TDD: (888)205-3223

For a Complete Report

For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc. ® (NORD). A copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see

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